Thanks for these Precision!! I will test with double_illumination to 
see if this is correct for me :).

Thanks a lot.

Fabian.


> 
> Vahur Krouverk wrote:
> >
> > It seems to be bug in version 0.5, not self shadowing. Changes list
> > indicates, that "double illumination bug is fixed", perhaps this is the
> > reason. If I have time, then I try to verify it (hopefully Nathan will
> > take a look at it, as he probably knows better this matter).
> 
> I've made some renderings and it seems, that it is bug in POV-Ray. By
> default smooth height-fields were double illuminated, but from version
> 0.5 it is changed to not double illuminate. Seems like smoothing is
> changing some surface normals such way, that in intersection point it
> appears to be faced backward (inward, into the mountain) and when double
> illuminance is turned off, then it is drawn unlit.
> 
> In order to test my theory, I've added light source under the
> height-field:
> light_source {
>   <0.0, 0.0, 0.0>
>   color rgb <1.000, 1.000, 1.000>*1.4000
>   translate  <-2.0, -2.0, -50.0>
> }
> 
> after this most of the blackness is gone, i.e. those backward surfaces
> are lit by this additional light.
> 
> Also, when camera is moved upward, then those backward surfaces are gone
> too, so seems like there is error in heightfield intersection (normal)
> calculation. I don't know, whether it is due to some coding error or is
> it some insolvable or hard-to-solve problem.
> 
> In order to make this scene work, there are following possibilities:
> 1. Create height-field image, which is smoother than current. I imported
> it to leveller and smoothed it, after this most of wrong illuminated
> surfaces were gone.
> 2. Double illuminate it by adding double_illuminate keyword.
> 3. If this can't be done (double illumination is unacceptable from
> artistic point of view), then use "rough" height fields or move camera
> upward.
> 4. If this is unacceptable, correct error in POV-Ray source code ;-)
> 
> HTH

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