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Note: IOR has zero affect when transmission uses a texture map.
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Bump Map
This category enables you to make a surface appear rough or bumpy. The rendering engine simulates shadows along the surface to create the textured effect. For example, you can define a Leather texture.
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The supplied texture map is automatically converted to a normal map and therefore must be given in a classical RGB format to encode the elevation. The amount of bump can be tuned through the scale factor. White (RGB 0, 0, 0) equals the highest points in the map, and while Black (RGB 256, 256, 256) equals lowest points in the map.
Displacement
This category enables you to make a surface rough or bumpy. Unlike bump maps, Displacement actually alter the geometry used to render the object.
This allows you to give more details to surfaces without paying the cost of detailed modeling, users can setup their materials to use displacement mapping, however displacement will create a greater rendering time than bump maps
displacement The supplied texture map is automatically converted to a normal map and therefore must be given in a classical RGB format to encode the elevation. The amount of bump can be tuned through the scale factor. White (RGB 0, 0, 0) equals the highest points in the map, and while Black (RGB 256, 256, 256) equals lowest points in the map.