[Bf-committers] Bump mapping computation issue

[Ton Roosendaal]

Hi,

Yes, bump mapping now happens in an object's local texture space,  
giving the errors as you've illustrated. This is an ancient issue in  
Blender.

> It seems to me that the problem comes from perturbated normal  
> computation made by blender.
> The formula for normal computation should be:
>     perturbated_normal=initial_normal+dI/du*dP/du+dI/dv*dP/dv
> where dI/du and dI/dv are the partial derivates of the texture color  
> in texture plane (these are scalars), and where dP/du and dP/dv are  
> the partial derivates of the position against texture coordinates  
> (vector dP/du "points" in the direction of greater "u").

Euh... I'm not sure about the notation you use here, but such parial  
derivates are used in Blender too. I think the only issue lacking is a  
proper transformation of the perturbation to global coordinates again,  
like the "shi->vn" is expressed in.

I think it's an interesting quality issue for Blender to solve once.  
Lemme give it a try now!

Thanks,

-Ton-

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Ton Roosendaal  Blender Foundation ton at blender.org  
http://www.blender.org