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This example demonstrates the effect of the fog Color. Note how color only changes the way the volume reacts to light, and not the volume transparency. A sphere shaped as the V-Ray logo has been used to confine the fog volume with the VRayEnvironmentFog set as the Volume material in the shading group of the sphere. The opacity of the sphere's Surface material has been set to be 100 transparent by 100 transparent by changing its Opacity Map to a black color. This means the Surface material has no contribution to the shading of the sphere, only the VRayEnvironmentFog material.

For the last 2 images, the fog Color has been mapped with a texture. The texture is plugged into a 3D projection node with the gizmo wrapping the object. 

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