Shading Languages

Shading Languages By Markus Kummerer

State of the Art Shading

Overview • RenderMan Interface • Shape vs. Shading • Types of Shaders • Shading Language • Examples • Interactive Multi-Pass Shading

RenderMan Interface • Powerful set of primitive surface types • Quadric surfaces • Polygons • Parametric surfaces • Hierarchical modeling, geometry • Constructive solid geometry • Camera model • Generalized shading model

Shape vs. Shading • Shape • Geometric configuration of objects • Shading • Calculates the appearance of an object in a scene under a set of light sources • Result defined by • Colors of the surface and the light source(s) • Position and orientation of the surface relative to the light • Roughness of the surface

Shading Pipeline • Three basic parts of the shading process • Emission at the light source • Interaction of the light with the surface • Atmospheric effects between the surface and the viewpoint

Types of Shaders • RenderMan Interface supports • Light source shaders • Surface shaders • Volume shaders • Transformation shaders • Displacement shaders • Imager shaders

Light Source Shader • Calculates the intensity and color of light sent by the light source to a point on a surface

Surface Shader • Determines the color of light reflecting from a point on a surface in a particular direction

Volume Shader • Generalizes the idea of atmosphere affecting light passing through space between a surface and the eye

Shading Language • Orthogonal definition • Rendering environment • Special data types • Uniform and varying variables • Integration constructs • Filtered map access • Function library

Examples

Example: Surface Shader

Example: Displacement Shader

Interactive Programmable Shading • OpenGL acts as an assembly language for shader execution • Compiler is introduced between the application and the graphics library

Interactive Programmable Shading • Results

Conclusion • Shading in software • Common technique for production animation • Offers generalized shading models • Provides a highly flexible approach • But is not interactive... • Shading in hardware is needed for interactivity

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Shading Languages