Details (CineRender Global Illumination)
These settings are available, as part of the optional Global Illumination effect, in the Detailed view of PhotoRendering Settings for the CineRender engine.
The effect of GI on glass is barely visible and can therefore unnecessarily take up render capacity. To avoid this, use the Glass/Mirror Optimization parameter. As a result, surfaces with a Brightness value (in the Transparency or Reflectance channels) greater than the value defined in this parameter will not be illuminated by GI. This may result in somewhat darker (but faster) renderings.
This parameter has no effect on Caustics!
For example, a lot of render time can be saved when visualizing a structure containing numerous large glass surfaces.
Tip: In order for this parameter to work, the surface channel “Color” must be disabled and no texture should be present in the Transparency channel.
Refractive Caustics/Reflective Caustics
Individually enables or disables Refractive and Reflective Caustics.
What are Caustics?
In the real world, caustics occur everywhere where light is clustered or reflected by refraction (see image above) or mirroring (e.g., on a metal ring).
There are two types of caustics in CineRender:
•Photon caustics in earlier versions of CineRender: Faster than GI Caustics but must be generated using individual light sources.
•Irradiance Cache GI Caustics: In conjunction with Primary Method IR. Not very precise but affect all luminous surfaces within a scene.
To generate caustics in previous versions of CineRender, it was necessary to create light source objects from which photons were beamed throughout the scene. In contrast, GI Caustics uses any available light source (exception: Only the reflected light of regular light sources can be included; use Polygon Lights instead).
GI Caustics require bright light (e.g. HDRI images with very bright regions or Area Lights) to come to fruition. Otherwise you can increase the strength of the Generate GI parameter in the Illumination channel of the Glass surface.
Tip regarding reflected GI Caustics: Reflected GI Caustics always require an active Reflectance surface channel. Otherwise, you can achieve the best quality caustics if GI Method is set to QMC.
Diffuse Illumination Only
Activating this option deactivates textures, reflections, light from surfaces illuminated directly by light sources, etc. All bothersome elements will be deactivated and only the brightness dispersion calculated by GI will be rendered. This also lets you judge the quality of the GI.
This option should be deactivated for the final rendering.
At top: normal rendering. Bottom: Rendering with active Diffuse Illumination Only option
(the sun is a real light source which means that its effects will be rendered
following the first reflection).
Show Samples
Shading points are displayed during the prepass phase for Irradiance Cache calculations. Sometimes these can be irritating when trying to assess the prepasses. To avoid this, disable the shading points’ display. The render time will be reduced slightly and the final render result will not be affected.