VRayMtl Options and Hardware Shading

Cutoff Threshold – A threshold below which reflections/refractions are not be traced. V-Ray tries to estimate the contribution of reflections/refractions to the image, and if it is below this threshold, these effects are not computed. Do not set this to 0.0 as it may cause excessively long render times in some cases. This parameter is not available when the renderer is set to GPU.

Use Irradiance Map – When enabled, the irradiance map is used to approximate diffuse indirect illumination for the material. If this is off, brute force GI is used, in which case the quality of the brute force GI is determined by the Subdivs parameter of the Irradiance Map. You can use this for objects in the scene which have small details and are not approximated very well by the Irradiance Map. This option is ignored when the renderer is set to GPU.

Fix dark edges – When enabled, fixes dark edges that some times appear on objects with glossy materials.

This is the standard Maya hardware texturing rollout. It enables you to choose which texture connected to the VRayMtl will be displayed in the viewport.

The Viewport Shading Quality option corresponds to the global viewport shading settings. They can be set individually for each material.

Viewport Shader Quality – Controls the VRayMtl's quality in the viewport. Note that this option overrides the global viewport shading setting for the material.

Use Global Settings – Uses the global viewport shading settings.
Low – Renders only the direct diffuse and specular (Fresnel, metalness and specular BRDFs) components.
Medium – In addition to the ones rendered with Low setting, it includes environment sampling (reflections and refractions), sheen and coat.
High – In addition to the ones rendered with Medium settings, includes normal/bump mapping, diffuse roughness and GTR gamma other than 2.0.