Materials define the visual properties of objects, for example:
- The color, reflection and refraction, and light emission properties of surfaces
- The scattering and absorption properties of volumes
- Modified geometric properties of surfaces such as displacement and normal perturbation (bump mapping)
Iray provides an example catalog of physically-based materials to apply to geometry, lights, and cameras. These materials are defined using NVIDIA Material Definition Language (MDL). Materials are defined based on distribution functions for reflection and refraction, for volume scattering effects, and for light emission properties.
Material definitions define "what to compute". The "how to compute" task is considered the domain of the renderer. This split of responsibilities enables all Iray rendering modes to use the same materials and is key to constructing a unified conceptual model of rendering.