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19.3.2 Example: DrmMapping

This example demonstrates DRM of control inputs.

See
The virtual world contains four target objects as it initially displays: three in a central column (red, green, blue) and one to the right (magenta). A screen shot is provided in figure 19.5.

Do

• Drag the mouse (first button with SHIFT) in the display or use the ARROW keys (with SHIFT) to orbit the view in heading and elevation about the world origin.
• Drag the mouse (first button) on the top (red) target or use the ARROW keys to translate it along the display X-Y axes.
• Drag the mouse (first button) on the middle (green) target or use the ARROW keys to rotate it about the display Y axis.
• Drag the mouse (first button) on the bottom (blue) target or use the ARROW keys to scale it along the display X-Y axes.
• Drag the mouse (first button) on the right (magenta) target or use the ARROW keys to roll the target like a trackball relative to the display.
• Repeat the drag operations from different view directions.

Observe

• All target operations use mouseover to enable the operation.
• All coordinate mapping uses DRM, meaning that manipulation of targets occurs relative to the display and will always seem intuitive regardless of view direction.

The first code sample below is from the DrmMapping example class. It shows only those portions pertaining to the translation target and DRM mapping. DRM mapping is provided by the utility building block buildDrmTranslationMapper from the IntuitiveBlocks class, which is shown in the second code sample. This block and others like it combine the framework's intuitive mapping blocks into individual modules specialized for a given type of geometric manipulation.

Notice in the example code how two different forms are used to specify the DRM mapper's source space reference node. The first case, for DRM translation, uses dynamic source node specification. It specifies the source node as null, indicating that the source node is to be defined by the view associated with the input drag event's source display. For this form, the local-to-Vworld read capability must be set on all the view platforms in the application from which the mapper might receive events. The second one, for DRM rotation, uses static source node specification. It sets the source node explicitly as the view object, in which case the transform read capability is automatically set on the view object by the DRM plug-in. This approach is simpler, but can only be used if the application has a single view.

... 
// setup manipulation targets 
/// translation target 
AffineGroup affineXlt = new AffineGroup(new TestThing( 
 TestThing.BOX_TRANSLATION, TestThing.BALL_DEFAULT)); 

affineXlt.getTranslation().initActuation( 
 new Vector4d( 0, 3, 0, 0)); 
getWorld().addSceneNode( affineXlt); 
... 
// setup manipulation controls 
/// manipulation draggers, first button 
InputDragSplitter relDrag = new InputDragSplitter(); 

ActuationBlocks.buildRelativeDragger(relDrag, 
 getView(), Input.BUTTON_FIRST, 
 Input.MODIFIER_NONE, Input.MODIFIER_NONE); 

/// manipulation mappers 
InputDragTarget mapper; 

//// Ex: let event source display define source node 
getView().getView().getViewPlatform().setCapability( 
	 Node.ALLOW_LOCAL_TO_VWORLD_READ); 

mapper = IntuitiveBlocks.buildDrmTranslationMapper( 
	 affineXlt, null, true); 
relDrag.addEventTarget( mapper); 

//// Ex: use view object as source node 
mapper = IntuitiveBlocks.buildDrmRotationYMapper( 
 affineRot, getView(), true); 
relDrag.addEventTarget( mapper); 
...

... 
/** 
Creates an intuitive drag mapper and corresponding source 
drag mapper, configures them for DRM translation in view X-Y, 
and connects them to the target object. 
@param target Target object. 
@param view Source display. If null drag source is used. 
@param cumulative True if drag actions are cumulative. 
@return New building block. 
*/ 
public static final InputDragTarget 
 buildDrmTranslationMapper(AffineGroup target, 
 AppView view, boolean cumulative) { 

 // use target translation node as source space 
 DirectSourceDragPlugin plugin = 
  new DirectSourceDragPlugin( 
 target.getTranslation().getTargetNode()); 

 // build source mapper for target X-Y translation 
 SourceDragMapper mapper = new SourceDragMapper( 
  target.getTranslation(), plugin); 
 mapper.setCumulative(cumulative); 

 // build DRM mapper 
 DrmDragPlugin drmPlugin = new DrmDragPlugin(); 
 if(view!= null) drmPlugin = new DrmDragPlugin(view); 

 IntuitiveDragMapper drmMapper = new IntuitiveDragMapper( 
  mapper, drmPlugin); 

 // scale input drag 
 return new InputDragFilter( drmMapper, 
  new ScaleInputDragPlugin(new Vector2d(.025, .025))); 
 } 
...

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