• 16 Light path expressions

16 Light path expressions

A light path expression (LPE) expresses a series of light and object interaction events using symbols to describe the reflective and tramissive properties of surfaces. NVIDIA provides other documents describing the structure of LPEs — their grammar — in detail. The following sections show the LPEs defined as part of Iray for Maya 2.0 that can serve as an introduction for artists to this powerful and flexible capability of Iray.
16.1Examples of light path expressions
Light path expressions are a complex and powerful way to control the content of various canvases. Some artists may find it difficult to develop an intuitive understanding of LPEs — but it is definitely worth a try. This section gives you some practical hints for many typically useful tasks.
The example Maya scene LPE_example_scene.mb contains a simple setup with a few objects, a Sun and Sky environment light and a light emitting polygon plane. The scene is available for download at the [0x1] website.
In the following chapter this is used to explain LPEs and to split the image in a set of framebuffer that can be used for composing.