Compositor

The RealityServer Compositor is a set of commands that allows you to split your rendering up into separate components which are then later combined using operations to generate variations of the originally rendered image without having to re-render the content.

This is extremely useful where you need to generate hundreds, thousands or even millions of combinations of colours, texture and other properties of a scene but it is impractical to fully render all of these combinations. Of course this technique involves some compromises but in most use cases is it perfectly adequate and much faster.

Using these techniques you can perform a single, high quality render of your scene in a special mode which outputs a large quantity of additional image data and metadata. This information is then used to modify material and lighting properties of the scene without re-rendering.

The Compositor builds on Iray's Light Path Expression (LPE) feature as well as the rendering of multiple simultaneous buffers (up to 20 at a time). The entire system is implemented as a set of V8 Server-side commands in JavaScript and the source code is provided should you wish to customise the system.

It is important to understand that the Compositor is not using traditional alpha channel compositing. In fact alpha channels are not even present in the images being rendered. All compositing is performed through a linear addition of the image data. This has a lot of advantages, including removing ringing and edge artifacts frequently seen with alpha or depth compositing.