Bump map

A material's albedo (left) compared to its bump map.

The above material in-game.

A bump map is an RGB image that can be used to simulate a three-dimensional surface through a process known as normal mapping.

Each color channel in a bump map has a meaning:

1. The red channel defines horizontal facing (X-axis)

   0 = left

   128 = forward (facing viewer)

   255 = right

2. The green channel defines vertical facing (Y-axis)

   0 = up

   128 = forward (facing viewer)

   255 = down

3. The blue channel defines height (Z-axis)

   0 = deepest

   128 = maximum depth capable of receiving dynamic light (it's a bad idea to go under this)

   255 = at the material's surface

The three channels between them allow the engine to calculate a normal vector for every pixel, allowing it to generate shadows and highlights on a two-dimensional surface.

A bump map is largely useless for really flat surfaces like smooth concrete or metal, but even rough concrete sometimes has enough depth to it to make one worthwhile.

See also

• $bumpmap, for adding a bump map to a material
• Normal Map Creation
  • Normal Map Creation in The GIMP
• Normal2dudv a third party tool for converting normalmaps to Dx8-friendly du/dv maps.
• An old article that explains the concept well.