The diffuse amount map acts as a multiplier for the diffuse color setting. Applying a diffuse map of a simple grayscale brick texture (where the bricks are white and the grout is black) gives an effect that the material has no diffuse reflectance where the pixels of the map are black, up to the amount specified in the material where the pixels are white. A diffuse map can be used in conjunction with a pattern map to give more contrast to the diffuse reflection.