Method

The Reflection Multi-Bounce node simulates specular lighting of solid objects accurately with support for multiple bounces with varying roughness and other material attributes. Only specular interactions are handled by this node, making it a good compliment for a baked diffuse lightmap pass. By only processing specular bounces it can be more efficient than using the Pathtracer node.
Results are achieved by casting lots and lots of rays, randomly distributed, and accumulating the results. The sum of all the random rays ends up with a smooth, converged image over time. As such this node can be slow and may not be suitable for real-time use.

Typically, only a very small number of rays per pixel can be cast per frame at real-time rates – but to produce a converged image, hundreds or thousands of rays must be accumulated per pixel. It is possible to use the “Samples” parameter to control how many rays are cast per pixel per frame at the cost of longer frame times. However, the more common solution is to use continuous refinement. This casts few or even only one ray per pixel per frame, varying that ray randomly each time and averaging the result, so the image converges from noisy to smooth. When anything in the scene changes or animation occurs, refinement resets. This allows you to work on your scene using a fast but noisy render as you edit it; then leave it to refine for a few seconds to see how it looks when converged.

Attributes

Name Description
Path Tracer Shader Loads in Pathtracer shader.
Samples The number of rays per pixel per frame.
Max. Glossy Depth The maximum number of glossy bounces per ray.
Stochastic Path Termination Randomly kills rays as they bounce and reduce in energy, to increase performance by avoiding processing of low-energy rays.
Ray Bias Biases the ray start position away from the spawning surface – to reduce fighting artefacts in exchange for less accuracy.
Sample Clamp The maximum brightness allowed for a given ray.

Environment Map

Name Description
Environment Brightness Sets the brightness of the environment map reflections.
Environment Specular Toggles on and off environment map specular.
Environment Filtering Sets the brightness off environment filtering.

Inputs

Name Description Typical Node Input
Object Nodes 3D Objects noded Inputted into the node will be the only objects that have RT Multi-Bounce Reflections. 3D object
Environment Map The input for the environment map node. Environment map
Transform Modifier Links all transform properties to the input node. Null
Target Node Always faces the x-axis towards the inputs anchor point. Null
Local Transform Override Override the transformation values of the node, relative to its parent. Null

Outputs

All nodes connected to this node are treated as if flowing to the parent node, and inherits any transformation changes along the chain.