The Override Material node is a utility node provided with the V-Ray renderer. It allows a surface to look different, depending on whether it is seen through reflections, refractions, or GI.

With this material you get fine control over the color bleeding, reflections, refractions, and shadows of the objects.

If you wish to disable the material preview or adjust its quality to save processing power, you can do so from the Material Node.

Base Material –  Specifies the material node V-Ray uses while rendering the object.

Enable GI Material – When enabled, the specified GI Material overrides the Global Illumination in the scene.

GI Material – Specifies the material node V-Ray uses while calculating the GI solution.

Enable Reflection Material – When enabled, V-Ray uses the connected material node when the object is seen in reflections.

Reflection Material – Specifies the material node for the object, when the object is seen in reflections.

Enable Refraction Material – When enabled, V-Ray uses the connected material when the object is seen in refractions.

Refraction Material – Specifies the material node for the object, when the object is seen in refractions.

Enable Shadow Material – When enabled, V-Ray uses the specified material for the object's shadows.

Shadow Material – Specifies the material node that is used to render shadows cast from the object.

Filter – Creates a Filter color or texture for the BRDF material attached.

MATERIAL ID

Material Id Enabled – Enables the use of Material ID.

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

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 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 also 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.