Light Material

The V-Ray Light Material is a special material provided with the V-Ray renderer. This material is generally used for producing self-illuminated surfaces. This material's light emission can be used as indirect, as well as direct, illumination in the scene.

This allows for light sources of any shape. The Light Material may even be assigned at the object level and at the face level for self-illuminating only portions of a mesh.

||V-Ray|| > Light Material

||Create|| > V-Ray > Light Material (disabled Separate menu for V-Ray materials)

Light Color – This parameter controls the color of the light material. A Texture can also be applied and blended with the color, using the Mix Strength option.

Color Multiplier – A multiplier for the Light Color. A Texture can also be applied and blended with the value, using the Mix Strength option. Determine how the two are blended using the Mix Type option.

Opacity – A color to use as opacity for the material. Note that making the material less opaque does not affect the intensity of the self-illumination color. This is so that you can create perfectly transparent materials that nevertheless still emit light. A Texture can also be applied and blended with the color, using the Mix Strength option.

Emit on Back Side – When enabled, makes the object emit light from its back side as well. If this is off, the back side of the material is rendered as black.

Compensate Exposure – Used when rendering with the V-Ray Physical Camera. When enabled, the intensity of the material is adjusted to compensate for the camera exposure.

Multiply by Opacity – When enabled, the color of the light material is multiplied by the opacity texture. Otherwise, the color and opacity act independently (so-called additive transparency).

Material ID – The color used by the Material ID render element. You can also use a shader here.

Multimatte ID – The integer ID of the material to be used by the Multi Matte render element.

Round Edges Enabled –  Enables the round edges effect, which uses bump mapping to smooth out the edges of the geometry during render time.

Radius – Specify a radius (in world units) for the round edges effect. Since the actual geometry is not being changed and only the normals of the faces are affected, large values here may produce undesirable effects.

Consider Same Object Only – When enabled, the rounded corners are produced only along edges that belong to the object, which has the attribute applied. When disabled, rounded corners are produced along edges formed when the object with the attribute intersects other objects in the scene. 

Corners – Choose which edges are considered in the calculation. Possible options are:

Covex and Concave – Considers all edges. 
Convex Only – Only applies Round Edges effect to edges with convex angles. 
Concave Only – Only applies Round Edges effect to edges with concave angles.