6 Attributes, Positioning and Orientation 93
6.3 Orientation 102
Many PDMS elements have an Orientation attribute, e.g. SITE, ZONE, EQUI, SUBE, STRU, PANE, Primitives, etc.
Orientation in PDMS is expressed in terms of axes direction, e.g. Y is N and Z is U, meaning that the elements Y axis is pointing North and the elements Z axis is pointing Up. Only two axes need to be stated as the third axis direction is know because it conforms to the right hand rule, i.e. in this case X is E.
Axis directions do not have to follow Cardinal directions, they can include one or more angles and directions, e.g. Y is N 45 E, meaning that the Y direction is North 45º East or Y is N 45 E 30 U, meaning that the Y direction is North 45º East 30º Up are both valid directions. Any direction can be expressed in PDMS using this syntax.
Elements that have a rotation attribute have, essentially, their own axis system which is known as the frame of reference. For example, the Z axis for a cylinder (CYLI) primitive is along the length of the cylinder. If the Z axis is Up with respect to its owner, the cylinder is orientated in an ‘upright’ position. In order to place the
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cylinder horizontally, say with its Z axis pointing in an East/West direction, the orientation of the cylinderwould need to be expressed as Y is N and Z is E (and X is D)
As with positioning, orientation is given with respect to its owner and the same rules apply for owning elements that do not have an orientation attribute.
Orientations may be queried with respect to any other element that has a frame of reference by entering Q ORI WRT <element name> or <element type> in the Command Window. For example, Q ORI WRT /E1301 will give the orientation with respect to the element /E1301’s frame of reference, or Q ORI WRT SITE will give the orientation with respect to the elements owning Site’s frame of reference.
Frequently the orientation is required with respect to the World frame of reference. Entering Q ORI WRT /*
will give this orientation.
6.3.1 Display Axes on CE
An axes aid can be placed on the CE by clicking the Display Axes on CE button on the Utilities Toolbar or selecting Query>Axes… from the main menu. Both options also display the Define Axes form:
The axes are displayed at the origin of the CE and are labelled X, Y, Z, i.e. the local frame of reference. The Cardinal Directions checkbox toggles between the local frame of reference and the World’s Cardinal directions. The Label checkbox toggles the display of a label that shows the CE name. The Size textbox enables the size of the axes aid to be set. The default is 500mm.
The Close form menu has two options that close the form. The Retain axes option leaves the axes aid displayed and the Remove axes option removes it from the display.
The Select form menu options places the axes on the selected item, i.e. if a new CE is selected in Design Explorer, selecting the CE or Owner option displays the axes aid on the new CE or its owner, respectively.
The Pick and Pick Owner options prompts for an item to be picked and the axes aid is displayed on the picked item or its owner’s respectively.
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6.3.2 Setting Orientation using AxesThe Design applications have an Orientate form, displayed by selecting Orientate>Axes… from the main menu, via which an element may be re-orientated by modifying its axes directions.
The form displays, by default, the current X and Y axes directions, the third axes being automatically derived. The top axis option list contains X and Y and the bottom axis option list contains Y and Z. It is, therefore possible to set the required axes using these option lists. If one option list is changed, the other option list and the displayed third axis are updated. The direction of the selected two axes may be modified by entering a valid direction in the appropriate textbox. As soon as the Return key is pressed after entering a value, the other two axes are updated.
On opening the form or a new element selected, a ‘bounding box’ is placed around the extremities of the element and an axes aid placed at the elements origin, whether the element is displayed or not. On entering a new direction for one of the axis, the bounding box is re-orientated to the new orientation.
Clicking the Apply button re-orientates the element but retains the bounding box and axes aid. Clicking the
Dismiss button removes the aids and dismisses the form.
If an element does not have an orientation attribute a warning message is displayed.
6.3.3 Setting Orientation using Rotate
Rotating elements using the Appware in PDMS is carried using a Rotation Axis, the position and direction of which are set by the user.
Refer to Chapter 8, Introduction to Model Editor, for details of graphical rotation of elements.
Selecting Orientate>Rotate… from the main menu displays the Rotate form:
When the form is displayed, a Rotation Axis aid is placed at the origin of the CE. The aid shows the default direction of the axis and cardinal angle labels show the direction of positive rotation.
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The Cursor form menu contains the following options:• Element – this option prompts the user to pick an element in the graphic view. The Rotation Axis is placed at the origin of the picked element.
• Design Point – this option prompts for the selection of a Point, i.e. a Ppoint. • Pline – this option prompts for the selection of a Pline on a SCTN or GENSEC.
• Edge – this option prompts for the selection of a PANE edge. • Defaults… - this option displays the Cursor Defaults form.
This form enables the way cursor picks are interpreted when a position is picked in a graphical view.
The Pick Options setting specify how a pick along a linear item is to be interpreted as a position. The choices are:
Snap – (default) The position will be at whichever end of the item is nearest to the cursor. The textbox next to this option is not
applicable in the current context.
Proportional – a proportion, between 0 and 1, is entered in the adjacent textbox. The derived position will be at this proportion of the item’s length from the end nearest to the cursor.
Distance – a distance is entered in the adjacent textbox. The derived position will be at this distance from the end nearest to the cursor towards the cursor position A negative distance will give a position beyond the end.
Exact - The position will be exactly at the picked point.
The Pick Qualifier setting specifies how many picks will be used to identify the position, and how a single position is to be constructed from multiple picks. The choices are:
Single pick - the position will be as determined by the Pick Options setting for a single pick. Mid-point of two picks - each of two picks will be interpreted as determined by the Pick Options
setting and then the mid-point of the two will be constructed to give the final position.
Centroid of multi-picks - each of two or more picks will be interpreted as determined by the Pick Options setting and then the centroid of the points will be constructed to give the final position. Pressing the Esc key terminates the picking.
L
Any modified cursor defaults will remain in force for all subsequent picking operations until they arereset.
The Intersection menu options enables a position to be defined by picking two directional items using the cursor in a graphical view.
The derived position will be at the intersection of the two items or, if they do not actually intersect, at a point on the first picked item which corresponds to the projection of the second item onto the first.
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• Element - this option prompts the user to pick any element which has its principal axis pointing throughor towards the required position.
• Design Point - this option prompts the user to pick any design point , which is aligned through or towards the required position.
• Pline - this option prompts the user to pick any Pline which is aligned through or towards the required position.
• Edge - this option prompts the user to pick any PANE edge which is aligned through or towards the required position.
If the Rotation axis position is set using one of the methods described above, the Rotate form automatically updates the coordinate information. The coordinates may be edited or set manually by entering values in the appropriate axis textbox.
Having positioned the Rotation Axis, its direction may be set by entering a direction in the Direction textbox. If necessary, the wrt (with respect to) textbox may be used to identify the element whose axis system is to be used as the reference.
The required rotation angle is entered in the Angle (º) textbox. The entry may be positive or negative depending on the rotation direction required.
A different element may be selected for rotation position by using the pull-down at the top of the form: The pull-down has the following options:
• CE – this option uses the CE as the element to move
• Pick – this option allows an element to be selected from a graphical view.
• List – this option uses the elements in the current list. All elements in the list are rotated. Clicking the Apply button on the Rotate form rotates the selected element(s). Clicking the Apply button again will rotate the element(s) again.
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