Visualising a 3D Scene

The Render Module

The Render module generates the 3D visualisation output in IRIS Explorer ^TM. It takes Geometry data (see the Data in IRIS Explorer section) and produces a 3D scene from it. This chapter provides an overview of how to use the Render module.

The Render module takes the geometry data present at its input ports and combines it into a scene. It follows the concept of a camera pointing at scene. A wide range of controls are available via the pull-down menus along the top of the window and a pop-up menu, obtained by clicking with the right-hand mouse button in the window. Additional controls on the interface can be toggled on and off by pressing the right-hand mouse button in the window and selecting Decoration. Controls will appear around the edge of the window. When they are switched on, the window will look like this:



Figure 9.1: The Render module with the Decoration visible

Viewing and Picking in Render

Render supports two modes which determine how mouse interactions will be dealt with. These are:

• Viewing - camera parameters can be changed
• Picking - objects can be manipulated, or queried

The Cursor icon in the drawing area depends on the mode:

• Viewing - hand
• Picking - arrow

Switching between them can either be achieved using two of the decoration buttons (see Push Buttons in Render below), or by pressing the <Esc> key.

Viewers in Render

Changing the camera attributes is done via a Viewer. The default Viewer is called Examiner. Other viewers are available from the Viewing menu.

The mouse controls in Examiner behave as follows.
• Left-hand button - Rotate the scene (using a virtual trackball)
• <Shift> + left-hand button - Translate up, down, left, right
• <Shift> + <Ctrl> + left-hand button - Dolly in, out
Alternatively, these functions can be accessed via the controls displayed when the Decorations are switched on.



Figure 9.2: The Decoration functions

Picking in Render

There are two modes for picking in Render which can be switched between using the Viewing menu.

1. Pick/Edit mode

In this mode, picking is done by clicking the left-hand mouse button on an object in the scene. The selected object then has a red box drawn around it and you can then edit the objects:

• appearance using the Material Editor
• colour - using the Color Editor
• scale, orientation and location - using the Transform Sliders

These editors are available from Editors on the menu bar. See also Manips on the menu bar for manipulators which can be used to transform the selected object.

The selected object is also passed out of Render's Picked Geometry output port for use by another module. The Edit menu can be used to control the picking behaviour.

2. User Pick mode

Information about selected object is written to a Pick data type and passed out of Render's Pick output port for use by other modules.

Push Buttons in Render

When the Decoration is switched on, the buttons on the right-hand edge of the window deliver some of the most useful controls for viewing. The top seven are generic, the others are viewer specific. Their functions are:

Switch to picking mode

Switch to viewing mode

Bring up the help screen for the current viewer

Return camera to home position

Save the current camera position as the home state

Move the camera to view all of the geometry currently in Render (very useful for finding lost objects!)

Move the camera to seek the next selected geometry, and to centre it in the viewing area

Switch between perspective and orthographic cameras (Examiner viewer only)

The Menu Bar in Render



Figure 9.3: The Render module menu bar

• File:
  
  Options for printing and saving the current scene (in Inventor, VRML, or image format), and the environment.
• Edit:
  
  Controls the way in which picked geometry is passed out of the module. The whole scene may be picked, or individual components. In the latter case, single elements may be selected (when Single Selection is turned on), or the picked scene may be accumulated by picking on the separate elements (when Toggle Selection is turned on). In Shift Selection mode, the two behaviours may be switched by depressing the Shift key when picking.
• Viewing:
  
  Picking, viewer selection, special effects (fog, anti-aliasing, transparency). Also contains editor for background colour of scene. The background colour is saved when the map containing the module is saved.
• Editors:
  
  Material properties, colour, transformation - of currently selected object.
• Manips:
  
  Further ways to transform the currently selected object.
• Lights:
  
  Create and edit lights in the scene.

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© The Numerical Algorithms Group Ltd. Oxford, UK. 1999