[osg-users] transforming normals

Paul Melis paul at science.uva.nl
Fri Mar 20 09:03:09 PDT 2009

Paul Melis wrote:
> Can Hosgor wrote:
>> I'm writing a simple nodevisitor to compute the lightmap of a given 
>> node. This nodevisitor treats transforms and geodes specially, so 
>> that each vertex in the geometry is multiplied with the most recent 
>> transform matrix in order to obtain world coordinates. So far the 
>> above code works well except that i don't know how to transform the 
>> normals. Can I obtain the normal matrix directly from the 
>> transformation matrix, if so how?   
> If M is your transformation matrix then (M^-1)^T transforms your 
> normals (that's the transposed inverse of M).
You might have to rescale your normals so they become unit length again, 
after using the above matrix


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