Page History
This page provides information about the Light Cache GI Engine in V-Ray for SketchUp.
Overview
Light caching (called "light mapping" in older versions of V-Ray) is a technique for approximating the global illumination in a scene. This method was developed originally by Chaos Group specifically for the V-Ray renderer.
This rollout is available only if Light Cache has been chosen as either the Primary Rays or Secondary Rays GI engine in the Global Illumination Settings.
UI Path
||V-Ray Asset Editor|| > Settings > Global Illumination > Light Cache
(When Light Cache is set as the Primary or Secondary Rays engine.)
Parameters
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Example: The Subdivs Parameter
The Subdivs parameter controls the number of rays that are shot into the scene and the "noise" quality of the light cache samples.
Here is a scene rendered with different settings for the Subdivs parameter (all other settings are the same). As more samples are added, the noise is reduced, but the render times increase. When the Subdivs parameter is increased twice, the light cache takes approximately 4 times as long to calculate.
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Example: The Sample Size Parameter
The Sample size parameter controls the size of the individual light cache samples. Smaller values produce a more detailed lighting solution, but are noisier and take more RAM. Larger values produce less detail, but take less RAM and may be faster to calculate.
Here is a scene rendered with different values for the Sample size parameter. All other values are the same. Note the light leak from the wall on the right in the last image - this is because samples from the other side of the wall are quite large (because of the Screen Scale) and end up being used on the side facing the camera (compare this with the World Scale in the above example). Note the difference in the noise level between the samples as well.
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Example: The Retrace Parameter
The first set of images shows how the Retrace parameter can be used to reduce light leaks due to the light cache interpolation. The scene is an interior scene with parts of the exterior visible. The bright light cache samples from the exterior blend with the darker samples from the interior causing light leaks when the irradiance map is calculated. The Retrace option (with the default value of 1.0) successfully resolves the problem at the expense of slightly increased calculation time for the irradiance map. Without retracing, light cache samples from the bright exterior are mixed with the dark samples in the exterior causing light leaks. With light cache retracing enabled, the light leaks are successfully eliminated at the expense of slightly longer irradiance map calculation time.
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Disk Caching
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Notes
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