Re: [Algorithms] Scaling Models

[<ro...@do...>]

Jim Offerman  wrote:

>I think OpenGL handles normals in the same way (and if I am not mistaken,
>OpenGL also uses some sort of inverse transform on normals, instead of
>feeding them to the 'normal' pipeline, which I presume is to counter the
>effects of scaling etc. on the normals...)
>

Actually it needs to apply the transpose of the inverse of the matrix
to the normals, then renormalize, to be always correct.  But this
would be wasteful in the majority of the cases that the
transformations are orthogonal.  APIs need to have a provision for the
programmer to hint whether of not the transformations are orthgonal.