Hi
Instead of organizing and reorganizing the scene graph so that you have the
proper nine cubes that need to rotate together, why don't you rotate each
individual cube? You would define a cube that had colored faces, and that
could rotate in certain predefined ways on its own (or by passing data into
an animation method). You could give each cube a thread and update them
simultaneously, or you could use one thread and do the rotation in very
small increments so that it appears that the cubes are all rotating at once.
This would save you the trouble of performing costly scenegraph
manipulation. And if you made your cube generic enough that it could accept
all kinds of animation data, it would be easy to use in other kinds of
applications.
B.D.
>From: Fred Klingener <[EMAIL PROTECTED]>
>Reply-To: Fred Klingener <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Subject: [JAVA3D] Kinematic Inversions (Was: Java3D - Rubic's Cube)
>Date: Sat, 4 Aug 2001 19:04:46 -0400
>
>From: John Wright <[EMAIL PROTECTED]>
>Date: Saturday, August 04, 2001 3:17 PM
>
>
> >To make nine cubes rotate together you'll want to form them into
> >Transform groups. It might be hard to do this for a rubic's cube as the
> >nine cubes that need to rotate together change constantly.
>
>
>I've been meaning to bring up this subject for some time. The summer
>doldrums seem to be as good a time as any.
>
>The problem of modeling a Rubic's Cude on a scene graph is an instance of
>the general problem of representing kinematic inversions. "Kinematic
>inversions" can be roughly described as different mechanical behaviors that
>result from different fixities applied to a basic structure.
>
>Start with a fourbar linkage. A particular linkage that has fixed length
>links pinned in a fixed order has four inversions, the behaviors of which
>depend on which of the four links is considered as the foundation.
>
>Gear boxes or planetary gear sets might have a single kinematic structure,
>but the behavior (the ratio between input and output speed) depends on the
>fixity (which clutches are engaged or released) or the position of
>countershafts.
>
>A formal representation of a walking or running human figure would be based
>on successive kinematic inversions as first one foot is attached to the
>foundation while the other is free, and then they are swapped. I'm not
>sure
>why this problem hasn't motivated more interest in kinematic inversions.
>So
>far, I suppose, reorganizing the scene graph for every step of the figure
>has been so computationally expensive that it hasn't been seriously
>considered. Still, it may be practical some time in the future when we
>have
>more compute power and we're more interested in solving the physics
>directly.
>
>The Rubic's Cube is an extreme example. It's easy to draw the scene graph
>once the move (the rotation of a face) is decided. But to represent
>successive rotations of different faces, the scene graph has to be
>disassembled and reassembled.
>
>It seems clear that any particular inversion can be represented directly on
>the scene graph, but a different inversion requires reconstruction. Java
>3D
>certainly has the parent and child gets and sets to reorganize the scene
>graph, so the crux seems to be designing the super object that expresses
>the
>basic kinematic structure and that supplies the methods for construction of
>the scene graph that expresses behavior of the particular inversions.
>
>How 'bout it?
>
>Fred Klingener
>Brock Engineering
>
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