Hi everyone,
I'm currently working with a system that contains multiple coordinate
systems, organized through transform groups. Each transform group has a
PointArray under it. There is also a "global" point array whose transform
is identity. What I want to do is take a "global" point - one defined under
a transform group with the identity transform, and add that point to a
"local" system - one with a transform defining a rotation and translation.
The catch is that I don't want the point to move in the virtual world - I
want to convert the coordinates so that it can be "copied" to the local
system, but in the scene it looks like there is no change.
I tried to do this by getting the transform defining the local system,
inverting it, applying it to the global point, then adding the new point to
the local system. I thought the application of the inverted transform,
followed by the application of the original transform would cancel, but it
doesn't and the point appears out of place. Perhaps there is an element of
matrix multiplication that I am forgetting.
This is a pseudocode of what I tried:
clickPt = (pi.getClosestVertexCoordinatesVW()); // where pi is a
PickIntersection and getClosestVertexCoordinatesVW() returns the "global"
coordinates of that point
Transform3D tempTransform = new Transform3D(localSystem.t3D); // get
the transform which defines the destination local system
tempTransform.invert(); // invert this transform
tempTransform.transform(clickPt); // apply it to the point
localSystem.addPoint(clickPt); //add the point -> t3D will be
applied to it and cancel the application of tempTransform to result in no
overall change in position
Please let me know if you have any suggestions on how to do this!
Chris
__________________________________________________
Christopher Collins http://www.ucs.mun.ca/~a62cmc
Oceanic Consulting Corporation (709) 754-2357 [home]
Memorial University of Newfoundland (709) 749-4383 [cell]
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