actual implementation of LOD modification

Bernie Roehl ([email protected])
Thu, 29 Jun 1995 09:54:25 -0400

MR LEEMON C BAIRD III writes:
> I should have given more detail. As transforms accumulate, objects
> are transformed by the product of a series of matrices. An improved
> LOD would leave the object untransformed, and would transform the eye
> with the product of the *inverses* of those matrices, applied in the
> *reverse* order.

Yes. In fact, there are other important reasons for finding the inverse
of those matrices, having to do with optimizing the graphics pipeline and
improving esndering performance.

> For this sort of transform, the inverse is cheap to calculat>. For a
> general MatrixTransform it can be more computationally intensive

Which lead

  • a good idea...

    > the inverse only needs to be calculat>d once, when the file is parsed,
    > so it wouldn't be too burdensoli. It would also require that an
    > additional matrix be stored for each MatrixTransform node, but not
    > for the simpler transforms such as translation and scaleFactor.

    Again, having to treat the MatrixTransform node separately is a hassle;
    it's not clear to me that it offers us anything we want that isn't already
    in the Transform node.

    -- 
   Bernie Roehl
   University of Waterloo Dept of Electrical and Computer Engineering
   Mail: [email protected]    Voice:  (519) 888-4567 x 2607 [work]
   URL: http://sunee.uwaterloo.ca/~broehl