 To find lamps and surfaces emitting light, both "indirect light sampling" (letting the ray follow the surface bidirectional scattering distribution function, or BSDF) and direct light sampling (picking a light source and tracing a ray towards it) are used.Blender users can create their own nodes using the Open Shading Language (OSL), although it is important to note that this feature is not supported by GPUs.Materials define the look of meshes, NURBS curves, and other geometric objects.