I'm trying to dynamically adjust the bounds of a scene graph object so that the
"apparent" size
(i.e. percentage of the field-of-view i.e. span of the object in pixels)
remains the same
no matter what the VWorld "z" distance from the object to the eyepoint is.
That is, I'm trying to "undo" the shrinkage due to perspective.
Reason why is I'm trying to make a Raster Shape3D pickable.
Now don't worry, I've got the performance aspect of this covered.
I need help figuring out the amount by which I should shrink or expand the
bounding box
of the object as the view moves toward or away from the object.
(I'm going to use a Billboard to make sure the boundingbox stays with a face
facing the view.)
So far, I know how to get the eyepoint position in VWorld coords, so I can
calculate the VWorld distance from the object to the eyepoint.
I think I also know how to calculate what the size of the bounds should be
(in VWorld coords) if the "z" position of the object were right up forward at
the image plate "z".
Can anyone help with what function of the VWorld distance I should use
in expanding the bounds of the object as the object recedes further into the
scene.
Part of what I don't understand is how the viewing projection works and what
the
effect of that projection on my expansion function should be.
Eric
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