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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA
Computer animation / editors, Jaron S. Wright and Lloyd M. Hughes. p. cm.
ISBN 978-1-61209-078-8 (eBook)
C
ONTENTS
Preface vii
Chapter 1 Computer Animation Applied to the Recovery of Preindustrial Heritage: A New Approach
1
José Ignacio Rojas-Sola and Francisco Javier Contreras-Anguita
Chapter 2 Virtual Engineering in Augmented Reality 57
Pier Paolo Valentini, Eugenio Pezzuti and Davide Gattamelata
Chapter 3 A Survey of Popular 3D Soft-Body Animation Compression Approaches
85
S. Ramanathan and A.A. Kassim
Chapter 4 Virtual Emotion to Expression: A Comprehensive Dynamic Emotion Model to Facial Expression Generation Using the MPEG-4 Standard
113
Paula Rodrigues, Asla Sá and Luiz Velho
Chapter 5 Example-Based Performance-Driven Animation of an Anatomical Face Model
129
Yu Zhang
Chapter 6 Dynamics for Managing Occlusion of Buildings in Panoramic Maps
145
Neeharika Adabala
Chapter 7 Constraint-Based and Feature-Based CAD Systems and Applications
157
Ioannis Fudos and Vasiliki Stamati
Chapter 8 Computer Aided Geometric Design with Powell-Sabin Splines 177
Hendrik Speleers, Paul Dierckx and Stefan Vandewalle
Chapter 9 An Ontology of Computer-Aided Design 209
Udo Kannengiesser and John S. Gero
P
REFACE
During the last decades, computer-aided engineering (CAE) methodologies have deeply changed the way of designing and developing products, systems and services. Thanks also to significant hardware and software improvements, CAE techniques are widely used by designers from the early conceptual phases up to the final stages of engineering processes. At the industry level, these methodologies have become a fundamental tool to be competitive and to ensure high quality standards. In industrial engineering, computer-aided methodologies typically are instrumental for design teams in shape modeling, behavioral simulations, digital mock-ups and realistic animations. They are able to follow the development of a product from conception to production, also managing its life-cycle. Character animation is one of the key research areas in computer graphics and multimedia. It has applications in many fields, ranging from entertainment, games, virtual presence and others. This new important book gathers the latest research from around the globe in this dynamic field.
The heritage of the preindustrial period is today coming under examination more often, as engineering must accept the study of its evolution as a discipline, from a technical as well as a historical perspective.
Engineering therefore provides industrial Archaeology and the history of technology with an important element in order to complete the study of industrial heritage. These studies are generally considered from the perspectives of history, ethnography, philology and architecture, but do not usually include studies from an engineering perspective.
Chapter 1 provides a detailed examination of the infographic work carried out on a Manchegan windmill (La Mancha – Quixote), as an example of preindustrial heritage, in order to obtain a computer animation, so that the procedure followed can be extrapolated to other examples of preindustrial heritage.
One of the reasons for choosing the windmill is that flour mills represented an important nucleus of the economy and of the industrial and social development of society. For this reason its study is important, especially for industrial history.
The study and analysis of these windmills is especially important owing to their general state of abandonment and deterioration, including analysis of the techniques used in their construction and those used in the working of the windmill. Computer animation is a key element in the recovery of this interesting preindustrial heritage.
In addition, the chapter discusses the advantages of this technique compared with others such as virtual reality, and why the majority of museum interpretation centres already possess these tools.
CAD-CAE (Computer-Aided Design/Computer-Aided Engineering) techniques provide through computer animation a fundamental tool to present an integral study from the perspective of engineering of any example of preindustrial heritage.
The importance of this chapter resides in that it presents in an innovative and structured way the procedure for generating a computer animation of preindustrial heritage.
In Chapter 2 the authors discuss several approaches in order to integrate computer-aided engineering instruments into Augmented Reality environment. Engineers and designers often develop their creative ideas in front of a computer monitor using mouse and keyboard. Although the integration between numerical computation and graphics leads to the generation of very realistic digital mock-ups, they are still far from the real context and the user has limited interaction with them. The purpose is to illustrate how recent development in computer graphics and image processing can improve the realism and interactivity with digital mock-ups. Starting from the interactive modeling of 3d shapes, the chapter presents some examples about the integration of real-time mechanism motion simulation, structural and fluid dynamics analysis post-processing.
In Chapter 3, the authors review 3D dynamic mesh compression algorithms and investigate how vertex clustering, which chiefly contributes to animation coding complexity, affects compression performance. The authors finally conclude this chapter with observations that need to be effectively addressed by future 3D animation coding algorithms.
In Chapter 4 the authors present a framework for generating dynamic facial expressions synchronized with speech, rendered using a tridimensional realistic face. Dynamic facial expressions are those temporal-based facial expressions semantically related with emotions, speech and affective inputs that can modify a facial animation behavior.
The framework is composed by an emotion model for speech virtual actors, named VeeM (Virtual emotion-to-expression Model), which is based on a revision of the emotional wheel of Plutchik model. The VeeM introduces the emotional hypercube concept in the R4 canonical space to combine pure emotions and create new derived emotions.
The VeeM model implementation uses the MPEG-4 face standard through a innovative tool named DynaFeX (Dynamic Facial eXpression). The DynaFeX is an authoring and player facial animation tool, where a speech processing is realized to allow the phoneme and viseme synchronization. The tool allows both the definition and refinement of emotions for each frame, or group of frames, as the facial animation edition using a high-level approach based on animation scripts. The tool player controls the animation presentation synchronizing the speech and emotional features with the virtual character performance. Finally, DynaFeX is built over a tridimensional polygonal mesh, compliant with MPEG-4 facial animation standard, what favors tool interoperability with other facial animation systems.
Recent development of physics-based face modeling that emulates the anatomical structure including skin, muscles, and skull allows us to create detailed, realistic animations. However, synthesis of facial expressions on such complex models often involves significant manual work due to the difficulty in determining appropriate values of the muscle actuation parameters. Chapter 5 presents an example-based performance-driven method to automatically estimate facial muscle actuation parameters from markerless video footage. The authors method is based on an efficient face tracker which uses a facial deformation subspace model. During the training phase of the tracker a set of templates associated with the subspace basis is computed to alleviate the online computation. At runtime, the tracking algorithm establishes temporal correspondence of the face region in the video sequence by
simultaneously determining both motion and appearance parameters. Using a set of example pairs that consist of the appearance and animation parameters corresponding to the key expressions, we learn the relationship between facial appearances and animation parameters. It enables the animation parameters to be computed in real-time from the appearance parameters obtained by the tracker, allowing animation of the anatomical model at interactive rates.
Panoramic maps depict urban areas in oblique view. This form of cartography was prevalent from the late sixteenth century to the early nineteenth century, when there were not many skyscrapers in urban areas. But oblique view maps in the current urban scenarios suffer from loss of details due to occlusion among closely located multistory buildings. In Chapter 6 the authors leverage the time dimension to overcome the clutter in space dimension by introducing functional dynamics. The authors define a parameter called occlusion index for an urban scene at a given viewpoint. Solving the problem of occlusion involves devising methods for visualizing the urban scene that reduce/minimize the occlusion index. They explore occlusion reduction techniques that involve selecting optimal viewpoints, displacing buildings, making buildings transparent and changing building heights. The authors demonstrate these approaches by presenting screen shots of the solution applied to a prototype city block, and discuss the advantages and disadvantages of these solutions. This work is pioneering in its approach to applying animation in cartography, which has previously used animations only to depict time-dependent phenomena or fly-throughs.
A new generation of Computer Aided Design systems has become available in which geometric constraints can be defined to determine properties of large designs. The new design concept, often called constraint-based design or design by features offers users the capability of easily defining and modifying a design, but introduces the problem of solving complicated, not always well defined, constraint problems. Traditional parametric models can also be enhanced to partially support declarative constraint-based descriptions. In Chapter 7 the authors provide an overview of representation schemes for CAD applications. Then they present a survey of methods for geometric constraint solving appropriate for Computer Aided Design. The authors demonstrate how these representations and constraint solving methods can be combined or adapted to support a broad range of CAD applications by presenting two example cases of successfully using a feature-based constraint-based representation scheme to support two different CAD applications.
Powell-Sabin splines are bivariate C1-continuous quadratic splines defined on an arbitrary triangulation. Their construction is based on a particular split of each triangle in the triangulation into six smaller triangles. In Chapter 8 the authors give an overview of the properties of Powell-Sabin splines in the context of computer aided geometric design. These splines can be represented in a compact normalized B-spline basis with an intuitive geometric interpretation involving control triangles. Using these triangles one can interactively change the shape of the splines in a predictable way. The authors describe the simple subdivision rules for Powell-Sabin splines, and discuss some applications. The authors consider a new efficient spline visualization technique based on subdivision. The authors also look at two useful generalizations of the Powell-Sabin splines, i.e., QHPS splines and NURPS surfaces. The QHPS splines are a hierarchical variant of Powell-Sabin splines. They have very similar properties as the Powell-Sabin splines, and their hierarchical nature allows a local refinement of the spline in a very straightforward way. The NURPS surface is the rational extension of
the Powell-Sabin spline. By means of weights they give extra degrees of freedom to the designer for the modelling of surfaces.
Chapter 9 develops an ontology of computer-aided design, based on the function-behaviour-structure (FBS) ontology. It proposes two complementary views of the process of design. The object-centred view applies the FBS ontology to the artefact being designed. Integrating an ontology of three “design worlds”, this view establishes a framework of designing as a set of transformations between the function, behaviour and structure of the design object, driven by interactions between the three design worlds. Building on this framework, the process-centred view applies the FBS ontology to the activities defined by the object-centred view. This increases the level of detail and provides a more well-defined set of representations of these activities. The authors ontological framework can be used to provide a better understanding of the functionalities required of existing and future computer-aided design support.
Editors: J.S. Wright and L.M. Hughes, pp. 1-56 © 2010 Nova Science Publishers, Inc.
Chapter 1
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José Ignacio Rojas-Sola
*and Francisco Javier Contreras-Anguita
University of Jaén, Department of Engineering Graphics, Design and Projects,Campus de las Lagunillas, s/n, Jaén 23071, Spain
Abstract
The heritage of the preindustrial period is today coming under examination more often, as engineering must accept the study of its evolution as a discipline, from a technical as well as a historical perspective.
Engineering therefore provides industrial Archaeology and the history of technology with an important element in order to complete the study of industrial heritage. These studies are generally considered from the perspectives of history, ethnography, philology and architecture, but do not usually include studies from an engineering perspective.
This chapter provides a detailed examination of the infographic work carried out on a Manchegan windmill (La Mancha – Quixote), as an example of preindustrial heritage, in order to obtain a computer animation, so that the procedure followed can be extrapolated to other examples of preindustrial heritage.
One of the reasons for choosing the windmill is that flour mills represented an important nucleus of the economy and of the industrial and social development of society. For this reason its study is important, especially for industrial history.
The study and analysis of these windmills is especially important owing to their general state of abandonment and deterioration, including analysis of the techniques used in their construction and those used in the working of the windmill. Computer animation is a key element in the recovery of this interesting preindustrial heritage.
In addition, the chapter discusses the advantages of this technique compared with others such as virtual reality, and why the majority of museum interpretation centres already possess these tools.
*
E-mail address: [email protected]. Tel: +34-953-212452; Fax: +34-953-212334; Corresponding author. Professor Dr. José Ignacio Rojas-Sola. University of Jaén, Department of Engineering Graphics, Design and Projects, Campus de las Lagunillas, s/n, Jaén 23071. Spain.
CAD-CAE (Computer-Aided Design/Computer-Aided Engineering) techniques provide through computer animation a fundamental tool to present an integral study from the perspective of engineering of any example of preindustrial heritage.
The importance of this chapter resides in that it presents in an innovative and structured way the procedure for generating a computer animation of preindustrial heritage.
Introduction
A Google search for the term “computer animation” shows up 2,650,000 results, while a search for the term “heritage” gives 117,000,000 results. A search for both terms together gives 91,400 results (search carried out on the 22nd December 2008). This shows the increasing importance of heritage in any of its facets.
This importance can also be seen in the numerous prestigious international congresses on the subject, such as “World Heritage in the Digital Age" (organized by UNESCO's World Heritage Centre) or VAST Conferences (International Symposium on Virtual Reality, Archaeology and Cultural Heritage). We must also consider the existence of high-impact journals, such as the Journal of Cultural Heritage (JCR) among others, the large number of websites dedicated to the issue [1], [2], or the European Union’s 7th Framework [3].
The UNESCO World Heritage [4] defines heritage as “our legacy from the past, what we
live with today, and what we pass on to future generations”.
In terms of the virtual heritage which concerns us here, researchers believe that it can serve to encourage people to visit the actual site, and can provide a complement to such a visit [5]; visitors can benefit from the changes and opportunities it offers [6].
Current trends in work on virtual heritage point to three different steps: complete 3D documentation, 3D representation (from historical reconstruction to visualization) and 3D publication (from immersive reality to augmented reality) [7]. Many applications have been developed which deal with historical sites or buildings, and in 2000 it was already forecast that in the following decade work would be centered on virtual industrial heritage [8].
Industrial heritage has a close relationship with Industrial Archaeology. Much has been written on this subject, defining it variously as the discovery, analysis, record and preservation of past industrial remains [9], the discovery, cataloguing and study of physical remnant of the industrial past, in order to learn about significant aspects of the world of work and technical and production processes [10], or the study of material culture and aspects linked to production, distribution and consumption, in the future and un connections with the past [11].
Today there are many examples of industrial heritage that are about to disappear, and in many cases in ruins. Many organizations are working to study and analyze these cases, some linked to industrial archaeology, such as TICCIH (The International Committee for the Conservation of Industrial Heritage) [12], AIA (Association for Industrial Archaeology - UK) [13], or linked to the history of technology, such as SHOT (Society for the History Of Technology - USA) [14], as well as branches of UNESCO which study the many aspects of heritage; architectural, industrial, cultural, ethnographic, to name but a few.
The recovery of heritage is in many cases linked to the history of technology, as it is a fundamental element in the study of the technological evolution of any invention. Engineering Graphics, and more specifically infographic techniques, play an essential role in the study of the history of technology, given the universal character of graphic language, as is
shown by the large number of articles in print which deal with graphic reconstructions of various inventions and devices [15 - 19].
However, in many cases the efforts of conservationists, archaeologists and restorers are not enough. In particular, the heritage provided by ruined buildings and constructions, whether architectural or industrial, is often lost owing to the interests of urban development or the lack of a renovation project which could give life to the area and bring opportunities for work. This loss is more clearly shown in the case of preindustrial heritage1, which has been part of production processes, not only because of the wideness of its scope, but also because older machines suffer greater deterioration when they are no longer used.
On many occasions initiatives are in put in place to conserve examples of industrial heritage, for example Museums of Science and Technology, which are becoming increasingly frequent, as they are a way of safeguarding a form of culture linked to the socio-economic development of a given area [20]. This example is all the more evident in the case of elements related to proto-industrialization (windmills, watermills, fulling mills, or oil presses, among others), as they date from the preindustrial period, and their age makes them more susceptible to deterioration and disappearance.
The role of synthesis images in the conservation of industrial heritage has grown exponentially in recent years. They allow an area, building or object to be preserved and interpreted in ways otherwise impossible to imagine, using photographic techniques. The most important factor is however that when using virtual models, it is not necessary to disturb or modify the original item.
There are also other advantages, stemming from the computer animation itself. Firstly there is a socio-cultural objective in the conservation of the ‘collective historical memory’ of an area where a given type of heritage was prevalent, providing information on the evolution of that society. Secondly, there is a clear educational objective in showing details of an abandoned culture [21]. Thirdly, there is also technological interest, as the use of computer animation techniques and processes provides valued know-how. A computer-generated image should be as faithful as a figure in a journal, although this is rarely possible [22].
In sum, whenever an element of a society’s heritage is lost, it also becomes impossible to study, analyze and value its impact on that society.
This chapter presents a new approach to the use of computer animation techniques applied to an element of preindustrial heritage, the Manchegan windmill (La Mancha, Spain), which were built in the 16th century, and some of which remain in near-perfect condition today. The specific windmill under study is the ‘Sardinero’, one of the 10 which still stand in the area of Campo de Criptana (Ciudad Real, Spain); it has also been declared of special cultural interest by the Spanish Government. These famous windmills appear in the masterpiece of Spanish literature, Don Quixote, by Miguel de Cervantes.
The Windmill
The windmill is one of the devices that has most been used over the centuries to obtain flour, an essential part of the human diet. A detailed study of their working mechanisms [23-25] and
1
their design codes allows us to develop a computer model and conserve completely this example of heritage, leaving a legacy which can be studied by future generations.
Architecture
Although there are various different types of windmills both in Spain and in other countries, the original architecture of a Manchegan windmill has three different floors. The ground floor (cuadra) is where the cereal was received and the canvas sails were stored. The first floor (camareta) is where the flour was packed into sacks, and the second floor (moledero) housed all the machinery necessary for milling the cereal [26].
The windmill had a cylindrical masonry tower about 8 m in height, capped with a conical cover (windmill cap) made of zinc, about 3.5 m in height. This rested on a ring on the top of the tower, which allowed this part of the windmill to turn to face the prevailing wind.
Working
The way a Manchegan windmill worked can be explained using the following photographs, which were taken by the author.
Figure 1 shows an exterior view of the ‘Sardinero’ windmill in Campo de Criptana. The photograph shows different functional elements of the windmill, such as the sails (which would be covered with canvas to increase their surface area), the windshaft and the windmill cap. SAILS WINDMILL CAP WIND SHAFT UPPER WINDOWS
Figure 2. Close-up view of the sails.
Figure 3. Close-up view of the join between the sails and the windshaft.
Each windmill has two rotation systems: a horizontal system, formed by the windshaft, the sails and other elements which will be described below; and a vertical system formed by the windmill cap and the tailpole. This vertical rotation system allowed the windmill cap to turn so that the sails faced the prevailing wind. This was done by the miller, who would use
the 12 small upper windows around the windmill to determine which way the wind was blowing.
Figure 2 shows the geometry of the sails, which have become deformed over time. They measure some 16 m from tip to tip, and are formed by 2 central stocks, and each of the sails had the central stock, four long ways struts and 19 crossways struts, giving rigidity to the sail. Figure 3 shows the detail of the join between the sails and the windshaft, and the three struts which provide rigidity to the sails.
FIRST FLOOR WINDOW ENTRANCE TAILPOLE TRIPOD STONE MARKERS
Figure 4. Front View of the Entrance.
Figure 4 is a view of the front of the windmill, showing the only entrance to the ground floor (cuadra), the window of the first floor (camareta) which provided the only source of natural light, the tailpole, which allowed the windmill cap to turn into the wind, the tripod or support for the tailpole, and the 12 stone markers which marked the 12 possible positions of the tailpole.
Figure 6. Entrance to the ground floor, with the counterweight which was used to separate the milling stones.
In the entrance to the ground floor there was an area where the sail canvasses were stored (Figure 5), and where the counterweight hung (Figure 6). This counterweight could be pulled down manually in order to separate the two milling stones.
Figure 8. Beams (marranos) supporting the milling floor.
The spiral staircase (Figure 7) which leads up to the first floor runs alongside the two huge beams (marranos), which supported the second floor (milling floor) (Figure 8). On this floor there was a flour channel (Figure 9) through which the milled flour passed directly to be put into sacks.
The mechanism which separated the milling stones (relief mechanism) (Figure 10) was located on the milling floor, and was activated by the counterweight shown in Figure 6.
Figure 11 shows the runner and the bedstone, between which the cereal was milled. These stones were normally grooved to aid the milling process. The photograph also shows the outlet for flour which led to the flour channel shown in Figure 9.
MECHANISM FOR SEPARATING MILLING STONES
Figure 10. Stairway to milling floor.
BEDSTONE RUNNER
FLOUR CHANNEL
Figure 12 shows gearing between the wallower and the brake wheel (fixed to the windshaft), which were the gear wheels which transmitted movement to the milling mechanism. The brake wheel had 40 cogs, and the wallower had 8 segments in which the cogs fitted, giving a gear ratio of 1:5 (8/40). Therefore, when the sails turned (normally at around 9 rpm), the brake wheel transmitted movement to the wallower, which in turn drove the rotation of the runner stone via the iron wallower axle.
A further important element in the working mechanism was the brake rim, which was activated using a set of struts and a rope.
Figure 13 shows the joint between the tailpole and the windmill cap, which were joined by a wooden block called the fraile. This linked the tailpole to the roof structure of the windmill, which was strengthened by wooden ribs.
BRAKE WHEEL WALLOWER IRON WALLOWER AXLE BRAKE RIM COG
Figure 12. Detail of the gearing between the wallower and the brake wheel.
WINDMILL CAP STRUCTURE
FRAILE
TAILPOLE
Figure 14 shows the hopper where the cereal was housed and the channel which fed the cereal into the central hole in the runner stone.
Lastly, Figure 15 shows the roof structure (formed by perpendicular beams called madres and manzanos), which was the wooden structure on which the ribs of the roof section of the windmill rested, as well as the tailpole, which allowed the windmill cap to turn. It turned on a ring (rueda terrera), which was greased in order to avoid excessive friction. The photograph also shows the windshaft and one of the two stones on which it rested, the forestone (fuélliga), and the tailstone (rabote).
HOPPER CENTRAL HOLE IN THE
RUNNER STONE
CHANNEL
Figure 14. Hopper and channel feeding the hole in the runner stone.
WINDSHAFT ROOF STRUCTURE
TAILSTONE
Methodology
Computer animation forms part of an innovative methodology for the conservation, diffusion and updating of industrial heritage [27].
In order to systemize the process of acquisition, classification, treatment and distribution of the available sources of information dealing with the object of study (plans, photographs, documents, slides, analogue recordings, hard-copy texts) and thereby both improve the conservation of this material and help to generate formats with higher added value, a working methodology was developed, as shown in Figure 16.
UPDATING EXECUTION VERIFICATION TARGET MATERIAL Corrective actions
Figure 16. Diagram of the methodology proposed for the recovery and updating of industrial heritage.
The Updating stage is divided into three sections: • Location, classification, nomenclature and storage. • Digitalization of the original material.
• Classification in digital repositories. The Execution stage has four steps:
• Identification of the technical requirements. • Definition of functional features.
• Workflows between applications.
• Analysis of the creation and publication processes. The Verification stage has two parts:
• Development of tests. • Analysis and verification.
This methodology provides an organized sequence of procedures, structured in three stages. A computer animation forms part of the first stage of the procedure, digitalization of the original material, as it consists of creating a sequence of frames in sequence, which when played at an adequate speed forms a video animation.
There are many programs for modeling, synthesizing images and computer animation, and a comparative study of them [28] shows the most well known characteristics of each. Two of the most outstanding are Autodesk 3ds MaxTM and Autodesk MayaTM. Although either of the two could have been chosen for this study, Autodesk 3ds Max was chosen owing to the need to create particles (grains of wheat and flour).
One of the critical phases of this process was the generation of digital models of the object, in order to create realistic images from the original sources. The applications and processes used in this task are described in the following sections.
The work process followed these steps:
1. General outline of the virtual recreation of the ‘Sardinero’ windmill 2. Creation of CAD model with AutoCAD and import to Autodesk 3ds Max
2.1. Fieldwork 2.2. Modeling
2.2.1. From AutoCAD, by exporting .3ds files
2.2.2. From Autodesk 3ds Max, by importing .dwg files 3. Cameras and illumination
3.1. Camera movement. Creation of path 3.2. Illumination
4. Animation of working parts
4.1. Runner Stone raising mechanism 4.2. Brake rim mechanism
5. Materials and maps. Mapping coordinates 6. Creation of textures
7. Rendering and video creation 8. Postproduction
Development
1. General Outline of the Virtual Recreation of the ‘Sardinero’ Windmill
It is recommendable, when working with industrial heritage, to perform two sequences or videos: a virtual ‘static’ view, which shows the object and its surroundings, and a second, ‘dynamic’ view, showing the working of the object, following the logical order of the productive process.This is how the work has been carried out in the case of the ‘Sardinero’ windmill studied here, establishing a playback speed of PAL frames of 25 frames per second.
Given the nature of this work we decided to create a single file in Autodesk 3ds Max which included both sequences (static and dynamic) so as not to have to make adjustments in texture and illumination in various files.
Lastly, we chose .avi as the file format, defined by Windows as its Video for Windows technology, as it is a format which is compatible with most video players. The file was created from the frames rendered individually in .png format.
2. Creation of CAD Model with AutoCAD and Import to Autodesk 3ds Max
Although there are many existing procedures to digitalize industrial heritage objects in 3D [29], such as Empirical techniques, Topographic techniques, Laser scanning techniques or Photogrammetry, we have used empirical techniques, owing to their ease of use, their transferability and to the fact that precision measurement was not a determining factor. In addition, the geometry is relatively simple, with a cylindrical tower which could easily be modeled using CAD techniques, and from the perspective of engineering graphics this technique allows us to obtain all types of views, perspectives and sections of the windmill. This in turn allows us to make comparisons with other forms.Two examples of the plans obtained are shown in Figures 17 and 18.
Figure 17. Section Perspective of the windmill modeled in 3D.
The development of the empirical approach applied to the ‘Sardinero’ windmill is based on two fundamental previous sections: fieldwork and graphic reconstruction.
2.1. Fieldwork
The fieldwork necessary for the project includes both taking photographs and drawing sketches of the building and its mechanisms. The quality of the computer animation depends on that of the photographs, as the texture captured from them is applied to the model in order to provide a high degree of realism in the final video.
Figure 19. Transition from sketch to 3D CAD model.
We used a Nikon D-200 digital camera to take the photographs, with an ISO setting of 800. This allowed us to obtain clear images, and we took around 500 photographs of the
exterior and of the three floors of the windmill. The windmill was measured using a 10 m tape measure in order to draw the sketches. The inside areas and mechanisms of the windmill were measured using an engineer’s scale. As the windmill is not a precision-built construction, various references were taken and measurements had to be adjusted.
The precision of the final model depends on the accuracy of the sketches and measurements taken. It is also necessary to bear in mind that the geometrical data obtained also allow us to infer certain technological considerations, and to make possible comparisons with other types of windmills.
2.2. Modeling
After sketching, the next step is modeling, which is necessary in the graphic reconstruction to plan the virtual tour of the windmill. From the perspective of engineering, modeling is a powerful tool which allows for an accurate study of each part of the machinery, as well as giving an overall idea of how the different parts of the mechanism worked together.
Some of the measurements taken ‘in situ’ were not completely accurate, and so further measurements had to be taken in order to shed light on certain assembly details which were not totally clear.
The program used for modeling was AutoCAD. To obtain a model which is a faithful as possible to the original is a complex task, as there are often limiting factors, such as the measurement of certain elements which cannot be measured by hand, and other techniques have to be used. In this way the CAD model is obtained from the hand-drawn sketches (Figure 19).
Given that AutoCAD and Autodesk 3ds Max were developed by the same company, it is easy to exchange information between them; for example, a point with coordinates x, y, z in AutoCAD corresponds exactly to another with coordinates u, v, w in Autodesk 3ds Max. This is an added advantage, because although there are neutral exchange files such as IGES, STEP or VDAS, these files sometimes produce a loss of information.
This exchange of information can be made in two ways: 2.2.1. From AutoCAD, by Exporting .3ds Files
Using this method it is possible export all the parts which are necessary, avoiding the need to debug later all the non-necessary elements, but they must by solids surfaces, lines, 3D polylines or 3D faces, among others. However, there are some disadvantages:
Sometimes when working with complex geometry AutoCAD cannot obtain the 3ds file format. In order to avoid in Autodesk 3ds Max curved surfaces which have a multi-sided appearance, it is necessary to increase a variable in AutoCAD (facetrees) from a default value of 0.5 to a value of 10, which causes a notable slowing of the program.
For these reasons, we chose the second option:
2.2.2. From Autodesk 3ds Max, by Importing .dwg Files
The model created in AutoCAD can be imported directly with the extension .dwg, although it is necessary beforehand to configure the .max receiver file in Autodesk 3ds Max with a series of options such as the measurement units, considerations about AutoCAD primitives, geometry, layering and rendering options of the splines.
Once the model has been imported, the screen is divided into four windows, called graphic windows (Figure 20), in order to create the sequences from different angles and perspectives. The active window is marked with a thick grey line, and all options can be accessed from a contextual menu using the right mouse button.
Figure 20. Working Screen in Autodesk 3ds Max.
3. Cameras and Illumination
Cameras can be used to obtain personalized views of a scene much in the same way as with real cameras. Here, they need lens adjustments which are measured in millimeters.
Autodesk 3ds Max has two types of cameras: Target and Free. The first is centered on the given object and the area around it, giving an independent animation of the object, while the free type simple records a scene in the direction in which it is pointing, without being linked to a specific object. In the case of the ‘Sardinero’ windmill, we used target cameras to obtain general plans of the exterior views, and of the first and second floors. Free cameras were used to focus in specific elements or movements, for example the counterweight relief mechanism used to life the runner stone.
Although Autodesk 3ds Max provides a wide variety of groups of lenses, from 35 mm to 200 mm, in the windmill cameras with a focal distance of 24.29 mm were used, which is the default setting, in order to obtain wide angle views of the scene. As well as the lens, it is necessary to adjust the field of vision (FOV) which is measured in degrees (Figure 21). This
is linked directly to the focal length and measures the visible part of the scene. In the case of the default focal distance, the program adjusts the value directly to 45º.
Figure 21. Camera with adjusted FOV.
3.1. Camera Movement. Creation of Path
Although a free camera is usually the better option if it is in movement and a target camera is more useful in situations where the camera does not move, we chose to use a target camera to produce the static video of the windmill (that is, a virtual visit where the windmill is not working), animating both the ‘body’ of the camera and the objective.
It is very important to maintain a constant and appropriate speed during the path of the camera, and therefore movement constraints were used, which link objects to others or to the path of the camera. Autodesk 3ds Max offers different constraints, such as:
• Attachment constraint • Surface constraint • Path constraint • Position constraint • Link constraint • LookAt constraint • Orientation constraint
Figure 22. Path of the camera following a spline curve.
In this case, the path constraint has been used, so that the camera follows a spline curve previously created in Autodesk 3ds Max (Figure 22). Using the appropriate commands, the following path was created, which is the path of the camera outside and inside the ‘Sardinero’ windmill.
Once the path has been generated, this has to be assigned to the ‘body’ of the camera. Although this can be done directly, in this case it was done indirectly, by assigning the path to a false object (Dummy) and then linking the camera to this object. This allows us to create camera travelling, at the same time as the camera uniformly followed its path; this is very useful to position objects and measure dimensions.
A simple cube was used as the Dummy, with a pivot point in the centre, which was not rendered and which had no parameters. The link was then made between objects lower and higher in the kinematic chain.
Finally, camera lens was animated independently of the ‘body’ of the camera using key frames. A helper was also linked, and moved through the scene by movement transformations, which does not imply any changes in the geometry of the object, but rather a modification of its initial state.
The following figure shows the situation of the camera which travels the path through the windmill.
3.2. Illumination
Illumination is the most intricate and complex part of the creation of any scene, as it forms the basis of the work carried out with textures and materials, and also determines to a large extent the rendering.
In cases of complex examples of industrial heritage such as a windmill, simplicity should be a key factor, in order to find an optimum balance between rendering time and the quality of the result. The configuration of the materials in the scene will also be a conditioning factor. In this example, we have used different types of lights from Autodesk 3ds Max, including the Daylight system to simulate natural sunlight (Figure 24) with its various options, in which the software simulates the position of the sun at a specific time and date, and from a specific direction.
It is also necessary to activate shadows by selecting the ray traced type (Figure 25), which are very accurate, as AutoDesk 3ds Max calculates the shadows according to each ray of light which enters the scene. In addition, we activated the option which determines the transition between bright areas and areas without illumination, and the exponential attenuation of light with distance.
The other values are default values, and the color and intensity of the light are according to the geographical location selected earlier.
It is also necessary to include fill light which does not generate shadows in areas where the principal light does not provide illumination. This fill light projects light from a defined area rather than from a single point, and with a lower intensity than that of the principal light. In the windmill these lights have been placed in each of the small upper windows (Figure 26).
Figure 24. Simulation of sunlight.
Figure 26. Fill light situated in the upper windows.
4. Animation of Working Parts
The following working subgroups were studied and animated:
1. Runner Stone raising mechanism. Inverse kinematics was used, which allow the designation of the movements of objects higher in the kinematics chain through the movement of the objects lower in the kinematics chain.
2. Brake rim mechanism. Here, inverse kinematics was also used, as well as Free Form
Deformation (FFD), which allows elastic deformations of objects.
3. Creation and animation of ropes. Here the Reactor module has been used, and so once the approximate forms have been created, gravity is applied, giving a realistic curve.
4. Brake wheel–wallower. In this case we have used forward kinematics, that is, to determine the movements of the objects lower in the kinematics chain acting on the objects higher in the kinematics chain.
5. Obtaining flour from grains of wheat. This operation was carried out in two phases: in the first a Reactor module was used to achieve the effect of the grains of wheat, stored in the hopper, falling into the channel through an opening and from there falling to the milling stones. In the second phase, the particle systems were introduced, which are elements which generate groups of objects called particles, which behave as a single unit, and which allow the creation of real-time simulations of natural phenomena such as rain, dust and snow, among others.
6. Movement of the sail canvases. Here an independent simulation system called Cloth is used, which allows the creation and animation of deformable material. Autodesk 3ds Max also has a specific modifier called Garment Maker, which transforms geometric primitives into material patterns.
As it would take up too much space to give a detailed explanation of each of these subgroups, we have chosen two as examples: the runner stone raising mechanism and the brake rim mechanism.
4.1. Runner Stone Raising Mechanism
In order to animate this mechanism which separates the milling stones, we used inverse kinematics, which allows us to determine the movements of objects higher in the kinematics chain by controlling the objects lower in kinematics chain. This is more effective than forward kinematics.
Autodesk 3ds Max includes various methods to animate using inverse kinematics, such as
IK Solvers, and traditional methods, Interactive IK and Applied IK.
IK solvers are helpers which apply inverse kinematics to systems of linked objects. For example, there is a History-Dependent solver which is recommended in mechanical systems with sliding joints in inverse kinematics, as it has controls for damping, priority, and spring back.
Figure 28. Control Element and actions on the other elements.
Interactive IK allows the positioning of a hierarchy linked to objects in different frames, and Autodesk 3ds Max interpolates all the key frames. This is not an accurate method, although it uses a minimum number of keys. Finally, applied IK is a method which applies a solution in a range of frames, calculating the keys in each frame; it is more accurate that Interactive IK, although it creates a large number of key frames.
In this case we used inverse kinematics applying both methods. Once the necessary links between the objects had been established using Interactive IK, their behavior was observed, and the animation was carried out using Applied IK.
To animate the movement of the separation mechanism of the milling stones, the raising mechanism of the runner stone, the elements have to be renamed, as when the AutoCAD model is imported into Autodesk 3ds Max, a predetermined name is given to all elements in the scene, and these names are not clear when there are many elements. Therefore, it is necessary to re-designate all the elements (Figure 27).
Then, the control element for inverse kinematics is established. This is the element which will be animated manually, to be used as the basis for the animation (Figure 28).
The next step is to determine the links between the control element and the other elements. This is the most difficult and time-consuming step, as it is necessary to use helpers and to relocate the pivot points of some objects. We added 6 helpers, to allow for the interconnection between all the elements and the combination of movements of some of them, for example in the runner stone which must turn and rise at the same time.
Figure 29. Positions of helpers.
Figure 29 shows the functions of the helpers in the mechanism:
Helper 01: Linked to the runner stone (including rings), the wallower (including rings
and cogs) and to the iron wallower axle, which is the object higher in the kinematics chain. It allows the transmission of circular movement to these elements.
Helper 02: Linked in the same way as helper 01, and transmits higher and lower
movement hierarchy to this set of elements.
Helper 03: Linked to the lever-beam joint, acting as a link between this and the other
elements.
Helper 04: Linked to the exterior raising beam, allowing for two pivot points on this
element.
Helper 05: Linked to the exterior raising beam, at the point where this joins the interior
raising beam. Its function is to connect these two beams.
Helper 06: This helper is lower on the hierarchy than the interior raising beam and its
function is to create two pivot points and also to connect the interior and exterior raising beams.
In addition, it is necessary to link two elements which are already joined, helper 04 and helper 03. In the same way, helper 06 is linked to helper 05, and helper 02 to helper 05.
It is then necessary to define the constraints of the joints of each element, as each has six degrees of movement: rotation and movement along the X, Y and Z axes. The Rotational
Each joint has three sections referring to each of the three axes, and if the Active option is deselected, that axis is constrained; that is, if the active option of the x axis of the interior raising beam is deselected in the rotational joints window, the element cannot turn on this axis. In the same way, if the same option is deselected in the sliding joints window, the joint cannot slide along this axis. This is how the joints are defined for the rest of the elements of the mechanism.
The rings of the runner stone, the wallower, and the screw and bolts which form part of the mechanism do not have defined joints, as they are linked solidly to elements which already have these joints defined.
Once the links and joints have been established (rotational and sliding) interactive IK is used to check that the elements of the mechanism move correctly. The button select and rotate shows another transformation of the three available in Autodesk 3ds Max, which does not imply any change in the geometry of the object, but rather a modification of its initial state (Figure 31).
It can be seen that from a certain angle of the control element, the joints do not function as in real life; specifically, from 30º, the elements begin to intersect with one another. To solve this problem, other animation tools can be used such the Reactor plug-in, which allows the creation of key frames when objects interact according to the laws of physics.
Figure 31. Inverse Kinematics and select and rotate buttons.
However, it would be time-consuming to configure the scene using the Reactor module, and given that the runner stone has a movement of approximately 1 cm, for which the angle at which the control element turned was not more than 6º, this simulation is unnecessary. Therefore it is only necessary to apply the inverse kinematic solution using applied IK, which can be applied to any range of frames. The required animation is therefore obtained, as the program calculates the key frames for the other elements according to the control element and the links established.
4.2. Brake Rim Mechanism
Inverse Kinematics has also been used to simulate the mechanism which brakes the brake wheel. In addition, a Free Form Deformation (FFD) modifier has been used to achieve the elastic deformation of the brake rim (Figure 32).
In this case the elements which are present in the animation are the linking beam, counterweight beam, hook joint with windmill cap, counterweight-linking beam joint, linking beam-counterweight joint, pin flange, pin and bolt (Figure 33). The ring and the rim itself will be animated once the movement of the other parts has been determined.
The control element is the linking beam, which is also the real-life control element (Figure 34).
The links are then made between the control element and the other elements. A helper has been added, not to link objects, but to make possible the presence of two pivot points on the counterweight beam. This beam is then established as higher in the kinematics chain than the pin, pin flange, bolt, hook joint with windmill cap, counterweight-linking beam joint, as well as the helper, and lastly, the control element is designated as higher in the kinematics chain than the linking beam-counterweight joint.
The counterweight-linking beam joint is linked to the linking beam-counterweight joint; specifically, the counterweight-linking beam joint is made to follow the linking beam-counterweight joint, and finally, the constraints of the joints are defined in these elements in the same way as before, using the Rotational Joints and Sliding Joints options.
Figure 33. Elements of the brake rim mechanism.
As before, correct movement is checked using interactive inverse kinematics, turning the control element with respect to its y axis, and observing the behavior of the other elements. Applied IK is then used as it can be applied to a given range of frames. Once the animation of the beams has been completed, the brake rim and its metal ring are animated. For this, the FFD modifier is used, as it can model rounded deformations without arrises, adjusting the control points of a lattice.
Figure 34. Control element and actions on the other elements.
Figure 36. Cylindrical Geometry of the FFD modifier, and surface adjustment button.
Figure 37. Modifier adjusted to fit the geometry of the rim.
The selection which is closest to the geometry of this example is cylinder type, FFd (cyl). The geometry of the modifier is then situated in the desired location (Figure 36).
Figure 38. Control points selected two by two.
The lattice is then selected and its resolution and size is configured, so that it coincides as much as possible with the brake rim and the ring. The higher the resolution, the better the results in the elastic deformation of the object, but more time is required. In this case, the resolution of the lattice was set at 42 control points, giving a perfect fit with the geometry of the rim, and also allowing us to animate it quickly.
Figure 37 shows the geometry of the FFD modifier (cyl) after making these adjustments. The brake rim and its ring are then linked to the animation, similarly to the way objects are linked using the command Select and Link. Finally, the lattice control points are animated using key frames, defining an initial and final state using movement transformation. Therefore, the control points should be selected two by two (Figure 38) in order to achieve a good result, and to ensure that the elastic deformation of the rim coincides with the movement of the beams.
Figure 39 shows the effect of the FFD modifier on the geometry of the brake rim after moving the control points vertically upwards.
5. Materials and Maps. Mapping Coordinates
Autodesk 3ds Max uses materials to cover objects to imitate the effect of light on these objects. Maps or textures are elements which are applied to materials in order to achieve a realistic appearance, using mapping coordinates which are defined as how the objects are aligned using three-dimensional coordinates u, v and w.
Autodesk 3ds Max has various types of materials, and their choice depends to a great extent on the rendering motor used and the type of illumination, among other factors. In the case of our windmill we have used standard materials to give realism to the animation, which are found in the Material Editor (Figure 40). Below is a description of the process used for the ‘dustcover’, a piece of wood which covered the milling stones.
In many cases it is necessary to create a new material because it does not exist in the library contained in the software. In our case, as the element which is to be textured is formed by a series of wooden staves, a material was created for each stave with a similar texture, so that the final appearance of the surface of the element does not have repeated patterns.
It is also necessary to define the shader to be used, as this is the algorithm which calculates the appearance of the material according to the specified parameters. In this case the Blinn shader has been used (the default setting), as it renders simple circular projections and softens adjacent surfaces.
This shader has color panels to configure the Ambient, Diffuse and Specular colors, which determine the appearance of the final color of an object. However, we used maps and textures taken from images of the original model in the texturizing process, using the Diffuse component through another shader.
It is also possible to obtain better results by configuring some aspects of the indirect illumination in the rendering motor, although this takes more time. This decision depends ultimately on the designer.
It is then necessary to define the mapping coordinates in the element to be texturized. We have used the UVW Map modifier, with a projection gizmo, which defines how the map will be projected onto the surface and how the material will be applied (Figure 41).
Figure 42. Adjustment of dimensions of gizmo to those of the image.
Figure 43. Final Result of Mapping.
However, the visualization of the texture on the surface of the element it not correct, as the adaptation of the gizmo to its geometry implies uneven steps, and therefore when the
texture is applied it seems stretched or compacted. Final adjustments have to be made to ensure that the dimensions of the gizmo are proportional to those of the image (Figure 42).
Figure 43 shows the final result, which is very similar to real life.
6. Creation of Textures
Maps or textures are applied to the materials to obtain a realistic effect. In our case the textures (Figure 44) are taken from digital photographs taken of the real object and edited with Adobe PhotoshopTM.
Figure 44. Texture taken from digital photograph.
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Figure 45. Exterior ground of the windmill processed by Adobe Photoshop.
Figure 46. Wooden door from which repetition texture is extracted.
The digital model was divided into a number of pixels with color and intensity, giving images which Adobe Photoshop can work with. These textures can be repeated indefinitely without the sensation of a repeated pattern. This is shown in Figure 45 applied to the ground of the exterior of the windmill. The upper part of the image has not been processed with
Adobe Photoshop and edges of the images do not match; however, the lower part of the image shows how this problem is solved.
Figure 47. Image with corrected perspective and area to be cut selected.
The first step when using Adobe Photoshop is to select the color mode RGB (Red-Green-Blue) and the 8 bits /channel option, which is a standard mode found in televisions and color monitors. Files used should be saved in format .psd. The first step is extract the area of the photograph (texture) which is to be applied, using the lens correction and cut tools. The example shows the process used for the wooden door of a food store (Figure 46).
The lens correction tool is used to correct the perspective, eliminating the divergence of parallel line, and the cut tool is then used to extract the desired area of the photograph (Figure 47).
As digital photographs are already illuminated, it is necessary to adjust the brightness in order to ensure that the textures extracted are not excessively bright. The brightness has therefore been reduced by between 10% and 20% in photographs taken inside the windmill, and between 25% and 30% in photographs taken outside.
Once this has been done, the image is cut and adjusted, obtaining a texture which can be repeated on the model without clear edges. This is undoubtedly one of the most complex stages of the work, to give a texture which has a high degree of realism (Figure 48).
7. Rendering and Video Creation
Rendering is a process which calculates the properties of objects before they are shown on screen, that is, it generates a synthesis of the scene created. Autodesk 3ds Max has a rendering motor called Mental Ray and an additional plug-in called VRay, which give excellent results thanks to the representation of light through rays. Rendering is done in the active window, which is marked by a thick border (Figure 49).
Figure 50. Render process window.
The Rendering drop-down menu includes the Render command where the configuration is done, defining the rendering motor, the range of frames to render, the format and size of the images, among other factors.
We chose the format .png (Portable Network Graphics), with a color configuration RGB 26 bits (16.7 million), with alpha channel and interlinking activated, which is one of the best image formats for computer animation. The resolution of the image is 768x576 pixels, with a width to height ratio of 4:3, although the final video format is a DVD.
Once the configuration has been done, the rendering process itself starts, and a dialogue box shows the adjustments made and the progress of the process (Figure 50).
Before rendering the final image is configured, defining the range of color and the output levels of the final image. This stage is very important, as it controls the clarity of the colors of the scene (not the illumination), the intensity of the tones, the intensity of the standard lights, and adjusts the colors so that they correspond to an exterior scene.
Once the rendering process is complete, the frames are linked together using the Video
Post command, which allows the inclusion of many effects; this command is also found in the Rendering menu.
The first operation to obtain video is to include the rendered images to make up the list of images. Then the output format AVI (Audio Video Interleave) is set, as it a simple and standard digital video format, and a compression codec is chosen to reduce the size of the final video so that it is more manageable. The resolution of the final video file is also set, in this case PAL 768x576 pixels. We obtained a video of 720 MB for the static sequence (a virtual tour with the windmill not working) and a video of 8.41 GB for the dynamic sequence (virtual tour with of the working windmill).
The sequence is executed and the following window appears (Figure 51).
The following 25 images obtained using rendering show the degree of realism obtained in the computer animation process.
8. Postproduction
The final stage in any Project in the graphic conservation of industrial heritage is the post production or editing of the video, to create an audiovisual document combining effectively audio, video and text. The object is to give a clear idea of the heritage and its setting in the production process.
This stage has been carried out with Adobe Premiere, which is a very versatile and intuitive program with a wide range of video, audio and transition effects.
The final video has the configuration DV-PAL with the Standard 48 kHz, allowing it to be shown anywhere using any equipment, and with options which allow the user to personalize the video.
First, the sound and video files are loaded, and the title and subtitles are created using a text editor. These are then added to the timeline, to set the order and timing of each element, and the transitions between videos are established. Lastly, the video is exported with the necessary settings.
Conclusion
This project shows that to create a realistic computer animation requires a great deal of time and effort. This process is usually carried out by a team of designers equipped with powerful computers with various high-speed microprocessors, sufficient RAM and graphic cards with large amounts of memory. In our case, two people and three computers took almost one year to complete the project.
Another important conclusion to be drawn is the importance of the technical training of the person who carries out the virtual recreation of the apparatus and devices which make up the element of preindustrial heritage, as in order to create a true-to-life animation it is necessary to know how these devices worked and were originally designed. Without such knowledge, it would be impossible for example to reproduce real working speeds of the machinery in the animation. At the same time it is extremely useful to be familiar with forward and inverse kinematics, as it makes working with Autodesk 3ds Max much easier.
Generating a high quality computer animation requires great effort, not only in learning the main software packages used, but also in learning to use other graphic programs, such as video editing software and photographic software, which offer many possibilities.
There has been a great deal of progress in the field of virtual reality, for example augmented reality, which is especially useful in the design of virtual scenes where real-life images are mixed with virtual images. However, computer animation using specific software still gives very high quality results, which makes it very useful when the objective is to show in detail how old machinery worked and its environment.
Computer animation using specific software provides a better solution when dealing with complex machinery than a virtual reality in which the user interacts with the system, as the user would need to know in detail how the machinery worked. For example, in the case of a windmill, how to use the regulation elements such as the counterweight which operates the raising mechanism of the runner stone or the mechanism which controls the brake rim; this is specialist knowledge which a normal user is unlikely to possess.
