[Radiance-general] manipulate rtrace for desired outcome

[Mengdi Guo]

Hi,



Currently I'm using the ray tracing engine of radiance, trying to figure
out the ray paths connecting designated view points and light resources (in
cylinder and polygon type). In this process, I've encountered some
difficulties that I'd appreciate your assistance.

I'm mainly using light as primitive type, since I want to figure out the
possible ray paths between receiver point and artificial light sources.
However the ray paths is not what I’ve expected.

In the testing condition where there is one receiver and one polygon light
sources directly exposed to each other. The polygon light source is the
only light in this scene. The source and receiver are placed in the middle
of two building blocks. I’m controlling rtrace function with the parameters
‘ –ab’ ‘ –ad’ ‘–dj’ ‘– ds’ ‘-st’ ‘-ss’.

1.       No matter what parameters I’ve set for rtrace function, there’s
only one ray in the output. Yet, I’m expecting multiple rays emitted from
the receiver points to the light source, as described in radiance manual.

2.       I’d also like to know what parameters can control reflections
characters of rays. For instance, I want the rays to partly diffuse after
reflecting on the surface. The desirable condition is: for a bundle of rays
hitting the surface, 1) 70% of the rays will follow specular reflection,
30% will be scattered after reflection. 2) for the scattered part, I want
them to be reflected within an angle (e.g. 30 degree) to the specular
reflected ray.

Could you suggest me how to achieve the condition of 1 and 2 with radiance?
Is there any other suggestions on the setting of model or scene?

3.       Another question is: acknowledged that the emitted rays are not
evenly distributed for hemispherical sampling. I'm still wondering if it's
possible to evenly send rays with radiance.

Thank you very much with best regards,

Mengdi Guo
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