[Bf-cycles] Camera Ray is also Singular Ray?

[storm]

В Сб, 14/06/2014 в 23:16 +0200, Gottfried Hofmann пишет:
> Hello Cycles Dev Team,
> 
> according to Wiki, the "Singular Ray" is a property of reflection- or 
> transmission-rays: 
> http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Light_Paths#Ray_Types
> 
> But according to my tests, a ray coming directly from the camera is also 
> a singular ray.
> 
> Is this the intended behavior? According to the OSL spec, singular is a 
> property triggered by a scattering event, so a ray coming directly from 
> the camera should not be singular:
> 
> https://code.google.com/p/openshadinglanguage/wiki/LightPathExpressions
> 
> Cheers,
> Gottfried
> 

Singular mean that segment can be only connected in one way, so we have
no oportunity to connect vertices by sampling something else. Like
laser, or perfect mirror, or perspective camera. You can think in term
"specular" and "diffuse" verices as in many paper like Veach
dissertation.

Opposite example, diffusion to diffusion surface, or diffusion and
glossy with "Roughness" > 0 can be connected by many ways (sample
surface at other points), so we can use MIS or other tricks to reduce
noise w/o making bias.