Re: [Algorithms] Scaling Models

[Jamie F. <j.f...@re...>]

Off the top of my head: to get the normal back, you need to perform the inverse
scale on it, and renormalise.

Pass on the D3D / OpenGL gubbins, never used either :)

Jamie


John White wrote:

> If you set a scaling matrix as part of the transformation pipeline what
> happens to the normals?
> I currently use D3D\OpenGL to do the transformation but use my own lighting
> code. If I set a scaling factor to each of the 3 axes the angles of most of
> the faces in the model will change (unless the scaling factor is the same
> for all three axes). An extreme example is when XSc=ZSc=1.0f; YSc=0.0f; All
> normals will either become 0,0,0 (for triangles with a normal perpendicular
> to the Yaxis) or 0,1,0 for all other normals.
>
> Rebuilding the normal list is not an option as the models are shared
> multiple times with different scalings.
>
> Anybody else encountered this problem? And how does D3D\OpenGL cater for
> this?
>
> ----
> John White
> Senior Software Engineer
> Deep Red Games Ltd.
> jo...@de...
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