Iray Programmer's Manual

Recommendations for materials

The following tips can help you to provide physically plausible material settings for Iray and benefit from photorealistic results with less noise and faster rendering times.

  • Don't use pure white colors. Pure white materials are rarely found in nature. They should be avoided. Avoid diffuse color values such as RGB=[1,1,1] (pure white), which could, for example, be replaced with [0.7, 0.7, 0.7] for white paper. Only few materials, such as pure snow, can reach values as high as 0.9.
Figure 1. Pure white (left) compared with physically realistic white (right)
File: images/recommendation_material_white.jpg
  • Don't use pure black colors: Purely black surfaces are rarely found in nature. They should be avoided as such. An RGB value like [0,0,0] could for example be replaced with the value [0.04, 0.04, 0.04] for charcoal or fresh asphalt.
Figure 2. Pure black (left) compared with physically realistic black (right)
File: images/recommendation_material_black.jpg
  • Avoid perfectly reflective materials when possible. In nature, a reflectivity ratio of 0.7 is already considered high. Set reflectivity to [0.7, 0.7, 0.7] instead of pure white. Freshly polished silver or chrome can reach reflectivities above 0.9, but oxidation and dust reduces this already.
Figure 3. Perfect reflectivity (left) compared with realistic reflectivity (right)
File: images/recommendation_material_reflectivity.jpg
  • Decide if emitting objects have to also reflect light. In most cases, this will not be necessary and materials without any BSDFs are cheaper to compute. If you do need a full material, test its setting first before adding emission. Otherwise, the brightness of the emission will make it hard to spot problems with the material setup.
Figure 4. Improperly set up glowing material (left) compared to properly set up glowing material (right)
File: images/recommendation_material_glow.jpg
  • Alpha maps embedded in textures are not used to automatically create holes. Use the cutout opacity feature of the MDL materials to create holes in objects.
Figure 5. Cutout opacity feature
File: images/recommendation_material_cutout.jpg