This page describes the Environment Priority setting and how it affects renderings.
Environment Override
The Environment Priority setting must be explained in the context of the Environment Override option.
The Environment Override option allows V-Ray to override the global Maya/Max/etc environment (background). This can be done for the whole scene by using Environment override settings in the V-Ray renderer, or it can happen per V-Ray material using its own custom Environment map override. When a variety of environment overrides are at play then the Environment priority setting determines the one to use.
V-Ray provides individual control for the GI, Reflections and Refractions override from its Render settings which is handy for optimizing your scene. You may this way use a low resolution environment map for faster/cleaner GI calculations and keep a high resolution map for crisp reflections and refractions. Furthermore you can set a separate map for Secondary Matte Environment and this way all your matte objects will use the custom map for shading the reflections and refractions on them.
Environment for reflections and refractions can be discretely set and rendered per material with V-Ray. Simply link your custom map to the Environment slot of the VRayMtl.
Here are some terms to be aware of when thinking about Environment Overrides in general:
Background – What renders in the scene if all objects are hidden (black by default) and no dome light is used.
Secondary Matte Environment – The background environment seen in reflections/refractions of matte objects (can be different than environment background).
VRaySky – A natural candidate for Environment overrides.
Example: Environment Override
This example demonstrates the effect of the Environment Override parameter. In the first image, the Environment Override option is off and the scene is rendered with the default environment. In the second image, a Gradient map is assigned and used as a reflection environment.
Environment Priority Setting
Objects in a scene may have different environment override maps assigned to their material. The Environment Priority is a technique that allows you to choose which environment map to be dominant and to be used during rendering. Simply put, the Environment Priority is the precedent of one override over another when one overridden material is reflected in another overridden material, then in another and so on. The environment map with the greatest Environment Priority is used. The Environment Priority value starts from 0 for the lowest priority and greater values describe higher priority.
Example: Environment Priority
This example demonstrates the effect of the Environment Priority parameter. Here, a teapot and a mirror-like plane have different environment maps assigned to their materials. In the first example, the texture map of the teapot has a higher priority than the texture map of the mirror. Each object reflects its own environment map as seen from the camera. However, the mirror also reflects the teapot's texture map as seen from the camera. This happens because the teapot's environment priority value is higher.
In the second image, the texture map of the teapot has a lower environment priority than the texture map of the mirror. Again, each object reflects its own environment map as seen from the camera. This time the reflection of the teapot in the mirror has changed. It uses now the environment of the mirror material because it has higher priority.
If both materials have equal environment priority for their environment maps then they are rendered in each-other's reflections the same way as when directly seen from camera.
