The Environment section in V-Ray render parameters is where you can specify a color or a texture map to be used during GI and reflection/refraction calculations. If you don't specify a color/map, then the background color and map specified in the SketchUp Environment dialog will be used by default.
For all volumetric environment effects, check Volumetric Environment page.
UI Path: ||V-Ray Asset Editor|| > Render Settings > Environment rollout
Background – Sets a color or a map to act as a background during rendering. Press the checkerboard button to select a texture. If a texture is selected, it will override the color as long as the texture checkbox is enabled.
GI (skylight) – Specifies the environment (skylight) color.The effect of changing the GI environment is similar to a dome light. Note that Global Illumination (GI) must be enabled.
Reflection – V-Ray will use the specified Color and Texture during reflection/refraction calculations. Note that you can also override the reflection environment on a per material basis (see VRay Material | VRayBRDF) or a per map basis. If you do not enable the Refraction override, this group of controls affects both reflections and refractions. If you enable the Refraction override, then this group affects only reflections.
Refraction – Specifies the environment color for refractions. This color is ignored if there is an environment texture specified.
Secondary Matte – Specify a color/texture to override the Environment rays affecting Matte objects.
The above GI environment overrides have the following common controls:
On – Enables or disables the specified GI environment override.
Texture – Specifies a color or texture for the specified override. Note that Texture Enable must be enabled to have an effect on the scene.
Texture Enable – Enables or disables the specified GI texture.