[Algorithms] Scaling Models

[John W. <jo...@de...>]

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...

Privileged/Confidential Information may be contained in this message.  If 
you are not the addressee indicated in this message (or responsible for 
delivery of the message to such person), you may not copy or deliver this 
message to anyone.  In such case, you should destroy this message and 
kindly notify the sender by reply email. Please advise immediately if you 
or your employer does not consent to Internet email for messages of this 
kind.  Opinions, conclusions and other information in this message that do 
not relate to the official business of my firm shall be understood as 
neither given nor endorsed by it.