Dynamic size box in Java 3D

Question

Hi,
I have two problems regarding the dynamic box in java 3D:
1. how can I change size of the box during runtime? I want to draw a 3D bar chart like using box.
2. what is "Exception in thread "AWT-EventQueue-0" javax.media.j3d.BadTransformException: TransformGroup: non-affine transform"? I encountered this when using a percentage (a value / max value) to create a box.
below is my portion of code:
I have methods to set the propValue, maxValue, sideX and sideZ. I update these values using setter to change the Box, but I think I need to have one more method to update the box (calling createSceneGraph() ).
protected Group createSceneGraph()
visualRep = new BranchGroup();
float scaleFact = 1.0f; // scaleFact is used only for debugging purpose
float percentage = propValue / maxValue;
// I want to move the height to half of its height, they are different for each
// module since the height is affected by the percentage. But, every time I add
// percentage to the "itsHeight", it gives me error : Exception in thread
// "AWT-EventQueue-0" javax.media.j3d.BadTransformException:
// TransformGroup: non-affine transform
//float itsHeight = ( HEIGHT * percentage );
float itsHeight = ( HEIGHT );
// 1. Create the box
Box vis = new Box(
sideX * percentage * scaleFact,
itsHeight * scaleFact,
sideZ * percentage * scaleFact,
Box.GENERATE_NORMALS,
LCMPlanning.getInstance().getAppearance( this.getModule(),
LCMPhysical.DEFAULT_WALL ) );
vis.setCapability( Box.ENABLE_APPEARANCE_MODIFY );
// 2. Move the first box to the top of the ground level
Transform3D t3d = new Transform3D();
t3d.setTranslation( new Vector3f( 0.0f, itsHeight, 0.0f ) );
TransformGroup tg = new TransformGroup( t3d );
tg.addChild( vis );
tg.setCapability( TransformGroup.ALLOW_TRANSFORM_WRITE );
visualRep.addChild( tg );
return visualRep;
thanks a lot.
Daniel

Answer 1

Hi,
Nobody answered your questions so far? Here's my take.
Changing the size of the box at runtime:
The easiest way to do that is to scale the transform using transformName.set(double scale) or transformName.setScale(double scale).
Non-affine transform error:
I get this error every once in a while. With me it happens when I try to assign a value of infinity or a NaN (not a number) to one of the params in the transform. I suggest printing the params you are using to create the box.
sideX * percentage * scaleFact,
itsHeight * scaleFact,
sideZ * percentage * scaleFact,
You may not be specifying what you think you are specifying.
Hope that helps.