Le 09/06/2010 19:31, sparky nous fit lire :
> A new technical paper has just been uploaded which shows
> that an initial projection of the gradient is needed to do proper normal
> perturbation of height functions.
> 
> http://jbit.net/~sparky/sfgrad_bump/
> 
> Most of the paper is aimed at rendering on GPUs but an equation (eq. 4) is
> presented which produces Blinn's perturbed normal but in a unified (2D/3D bump
> function) formulation.
> 
> Section 5 gives more details regading differences though the analysis is given
> in section 3.
> 
> The point is that simply adding or subtracting the 3D gradient of the function
> gives visual errors and is not equivalent to the normal of the displaced
> function nor a good approximation. Since it is an easy fix I would recommend
> that it is worked into povray.

You are of course aware that it cannot be a fix: existing scenes might
rely on actual behaviour and the Guardians of the Temple will not allow...

If it is easy, you might suggest the code correction (on beta code ?).

The paper looks like scholar... but fails to have an abstract, explicit
demonstration and rely a lot on asserting evidences (without formal
demonstration/mesurement/estimation).

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