EVPS DEVELOPMENT PROCESS

One of the objectives of the research is to streamline the EVPS development process so that the amount of time and effort required to create interactive virtual prototypes of healthcare facilities can be reduced. The steps for developing information exchange workflows to develop the EVPS are as follows:

- Identify modeling and interaction tools

- Identify and list file format that can be exchanged between the applications - Test exchange of model information using different file formats

4.4.1 Design Information Workflows

The system and process design phase helps identify the ideal modeling and software implementation tools based on the goals and objectives established for developing the EVPS. While some projects may need to be modeled from scratch, others may already have existing highly detailed models used from the project team. Once the modeling application is chosen, it is important to identify the file formats (see Figure 4-11) that can be exchanged between the chosen software applications

The intent of testing various workflows is to transfer as much model content as possible into the Unity game engine to ensure that limited amount of modeling is needed within it. Experiments with transferring model data using different file formats tested the amount of data that comes through various applications and noted any issues or missing information. The tests Figure 4-11. Interoperable file formats to transfer geometry content between tools.

identify the most efficient workflow and record this design information exchange process from 3D modeling software to interactive tools.

Various workflows were tested to best utilize 3D content from different BIM authoring tools for use in the Unity game engine. The advantage of using existing BIM authoring tools, such as Revit Architecture was that it allowed the use of existing building information models for the development of the interactive virtual prototypes. For this purpose, workflows to transfer model content from building information modeling tools such as Autodesk Revit along with other visualization and 3D modeling tools such as Autodesk 3D Studio Max, and Google SketchUp. Another benefit of directly exporting models into Unity was that design changes made to the model in native authoring tool (such as Autodesk Revit) could simply be exported again with changes that would be automatically updated in Unity.

4.4.2 Information exchange challenges

During workflow development, certain interoperability issues were encountered while importing models from Revit into Unity which were primarily related to textures, lighting, and overall organization of the model hierarchy. Interoperability is the ability of several systems, identical or completely different, to communicate without any ambiguity and to operate together. Maldovan et al. (2006) and Dunston et al. (2010) note that the lack of interoperability inhibits development of virtual mock-ups. Data are lost when models are transferred between applications and when models are sent to immersive virtual environments. Furthermore, depending on the type of display output, most applications do not support 3D stereoscopic visualization of models in real-time.

While 3D meshes of the lighting fixtures did transfer successfully into Unity, the lighting characteristics did not. Lighting for the spaces can be added within the Unity engine. Typically, a

large amount of time is required in making the lighting as realistic as possible; hence successfully carrying through these characteristics can translate into potential time savings for the project team. One possible solution to this lighting issue could be incorporating the use of baked textures within the lighting workflow. By importing a facility model into 3D Studio Max and using render to texture for the objects, baked textures depicting the lighting effect can be transferred to the Unity model. However, this may also raise the issue of redoing this entire process whenever revisions are made to the design of the model in Revit before being transferred again to Unity.

4.4.3 Real-time rendering challenges

Building or facility models typically contain walls, ceilings and floors that partition space into rooms. The geometric content of these models comprises of 3D meshes, textures, and lighting attributes. Larger models have larger polygon count that requires more resources for rendering and can affect performance of the real-time simulation.

According to Funkhouser et al. (1996), visual realism with short response times as well fast and uniform rate is desirable in virtual simulation prototypes of facility models. The level of detail needed is quite high to purvey the sense of presence and realism comparable to the true constructed space (Nikolic 2007) ; Zikic, 2007). Sense of realism is low when response to user input is slow. Latency between user input and display response is the product of many system components – input devices, computation of world physic, graphical rendering routines and formats.

The higher the frame-rate (number of images displayed per second), the smoother (lagging is greatly reduced) the real-time images are presented. This allows users to experience the virtual prototypes of facilities to a greater level of immersion and interaction (Shiratuddin

2007). Occlusion culling for models where large portions of the models can be hidden or occluded by polygons in front of the user’s viewpoints can be used to improve frame rate.

4.4.4 Optimal information exchange workflow

It was found that the most efficient workflow for embedding interactivity in virtual prototypes was by importing files into Unity game engine as an FBX file format (see Figure 4- 12). One of the benefits of using a FBX file format was that when files were transferred within the Autodesk suite, it retained information pertaining to 3D meshes, texture and camera locations. However, when a FBX file format was exported into Unity, it lost any type of textural

information associated with the model and the materials and textures had to be reapplied. Since the Unity engine had an extensive in-built library of textures and material, basic realistic textures can be applied within Unity with relative ease although it requires additional effort. Other workflows, particularly through other visualization applications, may not encounter this texture issue, although it has not been uncommon to have similar issues when moving from CAD / BIM authoring applications to interactive game engines.