Le 18-04-17 à 17:48, MichaelJF a écrit :
> Am 14.04.2018 um 21:37 schrieb clipka:
>> Yum.
>> Looks crispy.
>>
> Many thanks, hope it is a little bit more crispy now...
> 
> Here my final image with SSS at the tiles implemented. It was a lot of 
> guess work since I did not really understand the central parameter of 
> translucency. The docs are a little bit silent about this parameter and 
> the sample source gives very high values. So I had to play a little bit. 
> But learning is no waiste of time;)
> 
> First I observed strange artefacts at the white tiles around the black 
> ones: Irregular thin black lines. Since they turned blue as I made a 
> test with a blue colored version of the round tiles, I played around 
> with the reflection parameters, but without any success. Then I came up 
> with the strange idea to use UberPov instead of POV 3.7: the artefacts 
> (and some radiosity artefacts under the "`cookie"' as well - can be seen 
> at my first post here) disappeared completely.
> 
> The remaining issue were the black tiles. I observed strange artefacts 
> at the surface and no specular reflection. I played around with the 
> parameters but got the best result by using a very dark grey finally 
> (White*0.0001). The SSS feature seems to call for some - even very small 
> - amount of colour and seems to run into problems by specifying no 
> colour (black) as the pigment.
> 
> Rendering time extended to 2 h 51 m 39 s at the same machine.
> 
> I have no other ideas what can be done with the floor so far.
> 
> Best regards
> Michael
> 

You are right, translucency break when you have zero value components in 
the colour. Don't use rgb <1,0,0> for your red, but something like 
rgb<1, e-5, e-5>

The sample use large values to model wax and some highly translucent 
stone, and also, so that the effect is more visible.
The translucency represent the average distance that light will travel 
into the object before comming back out and is a representation of the 
average light travel distance between interaction.
As the translucency value get similar, then larger than, to the 
thickness of the object, you start to see through that object.

Is your grout made out of a plane ? If yes, then you can slightly see it 
under the surface of the tiles. It can be seen as artefacts. Try carving 
out the body of the tiles into that plane, or model only hte part of the 
grout that lies between the tiles using many box and cylinders in an union.

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