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The IPR samples provides a separate Max Samples and Pixel Variance for IPR rendering.  By default, this is set lower than render settings for quick feedback.

Interactive refinement uses a technique to sparsely sample the image and then refine it over time to provide faster feedback on updating the scene. The levels are 0 - 6 where 0 is off and 6 allows the renderer to be the most aggressive at deciding how few pixels to update at a time. The fewer the pixels that are updated the more likely you may see some blurry or ghosting artifacts at first while it resamples the frame but provide you with an update hint more quickly.

Integrator

Lets you choose the Integrator to use for the render.  The default, PxrPathTracer is a fine choice for most rendering situations.

See the page for each integrator for information about their settings:

• PxrDefault PxrDebugShadingContext
• PxrDirectLighting
• PxrOcclusion
• PxrPathTracer
• PxrVCM
• PxrValidateBxdf
• PxrVisualizer

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