prman_20.Home

Introduction

The prman_20 branch of Laika's Shading Library is the last version based on the Physically Plausible Shading system and the RenderMan Shading Language.

The foundation of Laika's Shading Library is based on a few core concepts:

• One Material shader (template) is used to create surface shaders.
• Multiple Material shaders can be attached, as an ordered set of coshaders, to a given surface to layer multiple materials onto the surface.
• Displacement in each Material Layer is influenced by the displacements of the materials under it in an automatic, but user-controllable way. In this manner, a Material shader represents a true physical material and not simply a set of illumination responses.
• The illumination produced by light sources can be influenced by specialized coshaders called Light Effectors, which can alter any characteristic of the illumination produced by the light. In this way, a small number of atomic light source shaders can be used to create an infinite variety of lights and lighting effects. These Light Effector effects can be associated with light sources, surfaces, or both.
• An extensive Override mechanism. This allows any shader's effect or Override any shader parameter's normal value to be easily overridden in highly specific and broadly configurable ways within the scene in order to tailor the rendered image as needed.
• The Material shader itself is composed of a layered set of illumination Responses. Individual Responses are added to a given Material shader as determined by the characteristics of the material and the shader author. The interaction of these responses with each other and to illumination is, by default, designed to be energy conserving and physically correct.