bumpdisplacement

Bump displacement is a computer graphics technique that displaces the geometry of a surface along its normals based on a height or displacement map to create the appearance of relief. Unlike bump mapping, which only perturbs shading normals to simulate detail, bump displacement alters the actual vertex positions, producing real geometric variation that can affect silhouettes and shadows. It is often used as a form of displacement mapping that relies on a height map to drive the displacement amount.

In practice, a grayscale height map provides a scalar value for each texel that determines how far to push the corresponding point on the surface. The displacement is typically applied in the vertex stage or, more commonly in modern pipelines, during tessellation and the subsequent evaluation stage. A tessellation control shader can generate additional geometry, and the tessellation evaluation shader applies the height-based offset along surface normals. Proper results depend on the alignment of the height map resolution with the mesh density and the chosen displacement scale.

Trade-offs include a higher computational cost and the need for sufficient mesh density or tessellation to avoid visible artifacts. Displaced surfaces also require careful handling of UVs and may introduce seams or popping if the height data is not continuous or the tessellation level changes abruptly. Nonetheless, bump displacement provides more accurate interaction with lighting and shadows and is well suited for materials that benefit from tangible geometric detail, such as rock, wood, brick, and fabric surfaces.

See also: displacement mapping, bump mapping, normal mapping, parallax mapping.