Iray Programmer's Manual

Limitations

Result Canvases

Iray Realtime supports only the result and object_id canvas names from the Canvas names in render targets.

Simultaneous output to multiple canvases is not supported.

Iray Realtime cannot render light path expressions.

Materials

The Iray Realtime material model, which is based on MDL (Material Definition Language), has the following limitations:

  • The number of elemental BDSFs per material are restricted to a maximum of 16.
  • The total number of (procedural) texture functions for all materials is restricted to a maximum of 4096.
  • Texturing support is limited to the types bitmap, blend and noise.
  • Only Perlin noise is supported. Other noise types are not supported and will be rendered black.
  • Multiple bump maps per material are not supported.
  • User-defined MDL functions are not supported.
  • The material volume properties are ignored, i.e., no volumetric effects.
  • The rounded-corners feature is not supported.

Rendering

Iray Realtime has the following rendering limitations:

  • No volumetric effects.
  • No custom matte objects.
  • The number of supported light sources is limited to 128. If a scene has more light sources, they will be ignored. Which light sources are shown is undefined.
  • Light profiles are only supported on point lights.
  • Area lights are approximated with a point light.
  • IBL does not cast shadows except for the implicit ground plane shadow.
  • Emissive geometry does not illuminate the scene.
  • No support for refraction on transmissive materials.
  • Reflectivity and glossiness of the virtual ground plane is not supported.
  • HDR textures are only supported for environments. HDR textures on other material parameters are converted to LDR before rendering. This may result in some differences in comparison to the other Iray render modes.
  • No motion-blur.
  • Anisotropic reflectivity is not supported with IBL.
  • A limitation of the employed glossy IBL reflections technique may lead to light leaking from behind surface edges.
  • Tonemapping is applied to all overdrawn transparent fragments, resulting in brighter appearance.
  • No Bloom filter.
  • The instancing options do not have an effect on Iray Realtime. Since the speed concerns described in Instancing do not apply to this mode, instancing is always active.

Picking

Picking reports only the first hit as a result.