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Shading

Bump maps

Bump maps are grayscale textures you map to objects to create the illusion of surface relief (elevations and depressions) on an otherwise flat object.

With bumps maps depressions and elevations look real, but are not, because they don’t alter the geometry of the surface the way Displacement maps do. Bump maps just change the direction of the surface’s normals based on the bump map’s Alpha Gain value.

Use bump maps to create very shallow reliefs. For example, you can make objects look like they are embossed, have shallow rolling hills, and so on.

Because bump maps are not true surface relief, they:

• cannot cast or receive shadows
• cannot be seen if you silhouette the mapped object
• take less time to render than displacement maps

Note File textures that are used for bump mapping are usually connected via their outAlpha attribute. If the corresponding texture image file does not provide an alpha channel, then the bump effect may be missing when using certain image formats. To avoid this, turn on the Alpha is Luminance attribute in the Color Balance section of the File Texture node. For more information, see File.

Related topics

	About surface relief
	Texture mapping
	Map a 2D or 3D texture

Tips Map surface relief (bumps or displacements) to the Blinn surface material to reduce highlight roping or flickering. The soft highlights on Blinn surfaces are less likely to cause roping or flickering than the harder highlights on Phong surfaces. Although scratches are like little depressions, you can more easily achieve them with 2D texture.