hi,

On 10/09/2017 20:57, clipka wrote:
> Am 10.09.2017 um 21:22 schrieb jr:
>> do I understand this correctly?  if I trace some object with a regular
>> pigment it will work, but the trace will fail if the object's
>> pigment/colour is "not simple"?  seems .. strange.
> 
> No, the `trace` function works perfectly fine for what it was designed
> for: It gives you the point in 3D space where a given ray intersects a
> given geometric object. In and of itself, it has nothing to do with
> pigments whatsoever.
> 
> Likewise, the `eval_pigment` function works perfectly fine for what it
> was designed for: It gives you the colour of a given pigment for a given
> point in 3D space. In and of itself, it has nothing to do with geometry
> whatsoever.
> 
> And that's where the problem with UV-mapped textures arises: Since
> `trace` knows nothing about textures, and `eval_pigment` knows nothing
> about geometry, the two can only be combined for good effect if there is
> a direct mapping between geometry and pigment via 3D XYZ space. But with
> UV-mapping that's not the case, and hence the /combo/ of the two
> functions breaks down there.

thanks.

regards, jr.

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