Sampling (CineRender Global Illumination)

This setting is available, as part of the optional Global Illumination effect, in the Detailed view of PhotoRendering Settings for the CineRender engine.
Left (Discrete Area Sampling and Discrete Sky Sampling disabled): At the first point of contact, several samples are sent out in a hemispherical direction (this is exactly what the Hemispherical Sampling option is meant for).
Center (Discrete Area Sampling is enabled and Discrete Sky Sampling is disabled): In addition to the hemispherical sampling, several samples are also sent out in the direction of GI Portals and (polygonal) Area lights.
Right (Discrete Area Sampling and Discrete Sky Sampling enabled): In addition to the hemispherical sampling and the Area light sampling, additional samples are sent out in the direction of the sky.
Left (Discrete Area Sampling and Discrete Sky Sampling disabled): This is not a viable option for this particular Project. The image itself is very grainy (the result of random samples hitting the Area light). The shadows are even more grainy. Bright points are also visible, the result of very few random samples hitting the (HDRI) sky’s sun.
Center (Discrete Area Sampling enabled and Discrete Sky Sampling disabled): The general graininess has been greatly reduced because additional samples are being sent to the Area light (each point visible to the camera is analyzed, which results in a highly defined shadow for the Area).
Right (Discrete Area Sampling and Discrete Sky Sampling enabled): In addition to the hemispherical sampling and the Area light samples, additional samples are sent in the direction of the sky. This abolishes the bright points, because every point visible to the camera is precisely analyzed with regard to the sky’s influence (including its effect on the remaining project elements).
The description of the following settings applies to the QMC Primary Method. The same applies to the IR method, except that sampling takes places for each shading point, rather than for each pixel.
Method: Two methods of defining sample count are used:
Selecting Custom Sample Count lets you manually define the Sample Count value
Selecting Custom Accuracy lets you manually define the Accuracy value
Accuracy: Use this setting to define an optimized sample count. The optimal count depends on the Project (and in IR GI Mode, on the other Irradiance Cache settings as well) and of course the defined Accuracy value.
Sample Count: This setting defines the fixed number of samples to be used. A higher value produces a correspondingly better render quality (for QMC this can be seen in the graininess; for IR the number of spots is reduced).
Check Use Area Sampling to enable this method.
In order for this sampling type to work, the GI Area Light option must be enabled in the Surface’s Illumination channel.
Force Per-Pixel: This option is only advantageous in IR Primary Method. Normally every light will be taken into consideration for the cache when an Irradiance Cache is created. However, this does not work if you have very small, bright Area lights. The result will be spotty images. If you enable the Force Per-Pixel option, the calculation of the Area lights will be split from the cache and calculated separately (as the QMC method does by default) for each potential pixel (object surfaces but no backgrounds or skies, for example).
Check Use Sky Sampling to enable this method.
Force Per-Pixel: This option has advantages only for the IR Primary Method. When an Irradiance Cache is created, the sky will normally be sampled and taken into consideration for the cache. For bright regions (sun) or those with smaller surfaces, this method has limits and will result in spotty renderings.
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