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6.1. Image and region size

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These are controlled from the SettingsOutput plugin, but it is one of the few exceptions where you should not touch the plugin directly. The AppSDK has APIs for setting image and region size.

6.2. Image sampling and filtering

V-Ray has several types of image samplers. These are algorithms that determine how many samples to take for each pixel. This is combined with an image filter, which can soften or sharpen the final image.

The image sampler is controlled from SettingsImageSampler. These are the four types of its type parameter:

• type=0, Fixed sampler - It simply uses a fixed number of samples for each pixel. This is controlled by the fixed_subdivs parameter. This sampler type is not recommended.
• type=1, Adaptive sampler
• type=2, Adaptive subdivision sampler
• type=3, Progressive sampler

The progressive sampler produces whole images iteratively, refining them with each pass. The other samplers work on small "buckets" and only return an image when it is complete.

For details on the adaptive and progressive sampler see this page. You can also see what our CTO has to say about sampling: https://www.youtube.com/watch?v=tKaKvWqTFlw.

Some of the default values when you create (or if you don't) the SettingsImageSampler plugin are not optimal. They are currently kept for compatibility reasons. Here are some guidelines for changing them:

• min_shade_rate - Use a value between 6 and 8.
  
  For Adaptive sampler:
• dmc_minSubdivs - Keep at value 1.
• dmc_maxSubdivs - Start with 24 and increase if noise doesn't go away.
• dmc_threshold - Start with 0.005 and decrease it if increasing dmc_maxSubdivs doesn't help with noise. You could keep it higher like 0.01 of course, if you want fast renders.
  
  Progressive sampler:
• progressive_minSubdivs - Keep at value 1.
• progressive_maxSubdivs - Use between 60 and 100.
• progressive_threshold - Similarly to dmc_threshold, start at 0.005 and reduce if noise persists. Don't go below 0.001.
• progressive_maxTime - This is a render time limit in minutes, so unless you want a safety limit, leave it at 0.

Most filters have just one size parameter for the kernel radius. Catmull-Rom has no parameters.

• FilterBox
• FilterArea
• FilterTriangle
• FilterGaussian
• FilterSinc
• FilterLanczos (currently default in V-Ray for 3dsMax and Maya)
• FilterCatmullRom
• FilterCookVariable
• FilterMitNet - Mitchell-Netravali filter. It has additional blur and ringing parameters.

6.3. Global illumination

SettingsDMCSampler - use_local_subdivs=0

6.3.1. Irradiance map

6.3.2. Light cache

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6.8. Stereo rendering

6.9. Miscellaneous

The SettingsRaycaster plugin has one parameter of interest: embreeUse. You'd want to set this to 1 (default is 0), because it increases raytracing performance.

6.10. RT Engine

7. Minimal renderable scene

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