Diffuse

Diffuse reflection is the component of surface reflection where incoming light scatters approximately equally in all directions. A perfectly diffuse surface looks equally bright from every viewing angle — it has no highlights, no glare, just a uniform surface color modulated by the lighting direction. Idealized chalk or fresh matte plaster comes close to fully diffuse behavior; most real materials are partially diffuse.

Diffuse reflection is the part of surface response that gives us our perception of color. The 'red' of a red apple, the 'beige' of a beige sofa, the 'gray' of a concrete wall — those are diffuse colors. The specular component (the mirror-like reflection) doesn't carry color information in the same way; it just bounces back what's being reflected.

In AI rendering, diffuse properties show up implicitly through material descriptions. 'Matte painted plaster' or 'raw cotton' or 'unfinished wood' will produce mostly diffuse surface response — soft, color-carrying, low-highlight rendering. If your output is looking too shiny, the fix is usually to push the material descriptions toward more diffuse terminology: 'matte', 'unfinished', 'raw', 'soft'. The default AI behavior tends toward slightly glossier than reality for most materials.