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#declare Window_Glass =
texture{
pigment{ rgbf<0.98,0.98,0.98,0.8>}
finish { diffuse 0.1
reflection 0.2
specular 0.8
roughness 0.0003
phong 1
phong_size 400}
} // end of texture -------------- |
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max_trace_level: The meaning of the keyword "max_trace_level"
is easyly to recognize by the following effect:
By using transparent textures and materials we sometimes unexpectedly can
"look some dark side of things" - some parts of glass surfaces are gone black!
At a surface of glass the raytracer calculates the through passing of 2 interfaces. At 2 panes
one behind the other we have already 4 interfaces.
If there are located more than 2 panes of glass one behind each other somewhere in our scene,
so POV-Ray by default will stop calculating the tracing of the rays
after the 5th interface (this means inside the 3rd pane!),
because in general the surfaces more behind do not make any relevant contribution to the total brightness.
The according effect will take place by multiple reflection at mirror surfaces.
The threshold of the number if interfaces where the tracing of rays will stop is defined by the keyword
"max_trace_level". It's default value is 5, it can be set up to a maximum of 256..
There are many cases where this is not enough, than at these parts we see gray or nearly total black surfaces!
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global_settings{ max_trace_level 5 }
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global_settings{ max_trace_level 17 }
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Remedy against dark spots: To avoid these dark spots we should encrease
somewhere at the to of our scene file the max_trace_level by i.e. the following line:
global_settings{ max_trace_level 20 }
Attention: Don't overdo!
Don't use unnecessarily high values, because each additional interface have as a consequence
an additional calculation of rays for each point,
provided that the interfaces before were transparent at least a little bit!
(The right image neads a 4 times longer time for caclculation then the left!)
Test renderings in "QUICK" mode:
If for test rendering we have choosen a resolution like i.e.
"320x240, quick, mosaic"
glass surfaces are only shown in black or in the defined "quick_color"!
Transparency or filter are not calculated in this mode!
