Albedo

Albedo comes from physics, where it describes how much of the light falling on a surface is reflected back. Fresh snow has a very high albedo, asphalt a very low one. In rendering, the albedo map (base colour) is the pure colour information of a material, with no shadows, highlights or reflections baked in.

Why a photo is not an albedo map

Photograph a brick wall and the image also contains the direction of the sun, shadows in the joints and the reflection of the sky. Use that photo as a texture and the light in the picture is added on top of the light the render engine calculates, so the result looks inconsistent. A good albedo map has those effects removed, leaving flat, even colour.

Practical points

• Pure white or pure black albedo is almost never used; real materials do not reach those extremes.
• Very bright albedo values make light bounce too much in GI and leave rooms unrealistically bright.
• Even white paint is not fully white; a slightly lowered value looks more natural.

In architectural visualization, correct albedo values directly affect the light balance of interiors. The more light the walls reflect, the brighter the room is calculated to be, so choosing a colour is a lighting decision as well as an aesthetic one.