Re: [Algorithms] Scaling Models

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

Peter Warden  wrote:


>Just out of interest, one thing I did a while back when I needed to treat
>both normals and vertex positions uniformly when applying an animation
>matrix to them was set the W component of the normals to 0, whilst leaving
>the W component of the positions at 1. This worked because the animation
>matrix never contained a scale, and I just wanted to not translate the
>normals. Is this a well-known technique that I just haven't run across
>before, and is there any theoretical basis for it?
>

This is  the correct way to treat the w components WHETHER OR NOT
the transformation contains a scale. You never need to "translate
normals" because the translation of a vector (as opposed to the
translation of a point) is always the vector itself.   It is inherent
in the meaning of "vector".  See my response to the original post of
this thread.