Nicolas Alvarez <nic### [at] gmailcom> wrote:
> Hmm I don't think nonlinear transformations would cause the ray to be a
> curve.

  Well, the very definition of "non-linear transformation" *is* that
straight lines don't necessarily remain straight after the transformation.

  Conversely the very definition of "linear transformation" is that any
straight line remains straight after the transformation.

> Non-linear transf. are already possible in isosurfaces.

  In the same sense as non-linear transformations are "possible" for
triangle meshes (although not really, but almost).

  You are not really transforming the isosurface object. You are modifying
its function, which is a different thing (from the point of view of
raytracing). You can't do that for other primitives.

> All you need is a different matrix for each pixel. Or rather, instead of
> using a matrix you multiply with, use a generic function.

  Simply changing the direction of the ray according to a function, while
keeping the ray straight, is *not* enough to achieve non-linear
transformations of objects.

-- 
                                                          - Warp

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