Page History

...

Note that some specific image features, like high-frequency detail often found in fur and hair, or high-contrast zones, will likely always try to reach the maximum sampling, so some red will appear there. This is perfectly normal and doesn't slow down the rest of the rendering while ensuring the problematic parts of the image will clean up as per the user's settings.

...

UI Path: ||Render Settings windowToolbar|| > V-Ray Menu icon > Render Elements tab > VRayRenderElement > Sample  Sample Rate

Properties

...

The Sample Rate render element has no controllable properties.

Common Uses

...

VRaySampleRate can be used with both the Bucket and Progressive image samplers.

Bucket Image Sampler

The Sample Rate Render Element is useful for fine tuning render settings using a "red is bad" rule.

Below is a scene with minimal red in the Sample Rate Render Element, indicating that the sampler had a high enough Max Subdivs value to hit the desired noise level. 

In the next image, the sampler did not have a high enough Max Subdivs value to hit the desired noise level. The high amount of red shows that the image sampler cut off sampling before the image hit the desired noise level. Noise can be decreased by increasing the Max Subdivs parameter to allow the image sampler to reach the desired noise level. Click on the image to view a larger version.

The primary samples can be allocated to the complex areas of the image by increasing both the Max Subdivs and the Noise Threshold values. This way, V-Ray has available enough primary samples to lower the noise of the complex areas in exchange for an overall slight increase in noise, while still keeping the render times down.

Section
Column width 10%   Column width 40% Image Added The Sample Rate Render Element   Column width 40% Image Added Render time = 8m 37s, Max Subdivs = 30, Noise Threshold = 0.02, Min shading rate = 6 Sample Rate Render Element with not enough max subdivs. The Image sampler was mostly not able to reach the specified noise threshold.   Column width 10%

Alternatively, the image sampler can allocate primary and secondary samples by changing the Min shading rate value.

For this scene, increasing the Min shading rate will allow the sampler more secondary samples to focus on cleaning the lighting, GI, reflections and refractions. In exchange, some of the fog and high contrast areas are a bit noisier as there are not enough primary samples taken for those areas.

Section
Column width 10%   Column width 40% Image Added The Sample Rate Render Element   Column width 40% Image Added Render time = 14m19s, Max Subdivs = 18, Noise Threshold = 0.01, Min shading rate = 20 Sample Rate Render Element with not enough max subdivs.  Less primary samples were needed to hit the desired noise level since more secondary samples were taken.   Column width 10%