Shader Writing in Open Shading Language

Mitch Prater's interest in graphics began at age 12 when he set out to build his own "Pong" game based on an article in Popular Electronics magazine. Mitch graduated from hardware to software implementations with Fortran IV programmed on punch cards and a line-printer for output. Through the 1980's and 1990's he progressed through CRT terminals, dedicated graphics hardware, integrated GPU chips, graphics libraries, and finally into rendering systems with dedicated shading languages when in 1988 he began working at Pixar using the Pixar Image Computer and was introduced to the 1.0 alpha version of RenderMan. From there Mitch wrote shaders and created new shading and lighting techniques for use in Pixar's commercials, short films, and all the features from Toy Story to Cars; and then again from ParaNorman to Missing Link at Laika. Throughout a career that now spans nearly 40 years, Mitch Prater continuously developed new shading and lighting techniques, shader code libraries, and production shaders for feature films, animated shorts, and real-time games.

Preface

1. Introduction

2. Variables

2.1 Data Types

2.2 Compound Types

2.2.1 Arrays

2.2.2 Structs

2.3 Global

2.4 Built In

2.5 Primitive

2.5.1 Parameter Access

2.5.2 getattribute() Access

2.6 Options and Attributes

2.6.1 OSL Attributes

2.6.2 RenderMan Options and Attributes

2.6.3 User Attributes

2.7 Example Shaders

2.7.1 Global Variables

2.7.2 Built In Variables

2.7.3 Primitive Variables

3. Coordinate Systems

4. Conversion Shaders

4.1 Simple Types

4.1.1 Float to Color

4.1.2 Color to Float

4.1.3 Type Connections

4.2 Artistic to Physical

4.2.1 Base Color and Metallic to Specular Face and Edge Colors

4.2.2 Specular Face and Edge Colors to Complex Refractive Index

5. Color

5.1 Color Models

5.1.1 RGB

5.1.2 HSV & HSL

5.1.3 CMYK

5.1.4 Spectral

5.2 Color Spaces

5.2.1 CIE 1931 XYZ

5.2.2 xyY

5.2.3 Television Standards

5.2.4 Web Standard

5.2.5 Academy Standards

5.3 Color Space Conversions

5.3.1 sRGB to Rec. 709

5.3.2 Rec. 709 to ACEScg

5.3.2 sRGB to ACEScg

6. Spaces and Transformations

5.1 2D Space

5.2 3D Space

5.3 2D Transform

5.2 3D Transform

7. Texture Patterns

7.1 File Names

7.1.1 String Functions

7.1.2 Tokens

7.2 t Inversion

7.3 Metadata

7.4 Data Access

7.5 Projections

7.5.1 Orthographic

7.5.2 Shear

7.5.3 Spherical

7.5.4 NDC

7.5.5 Rounded Cube

8. Procedural Patterns

8.1 Spatial Conversion

8.1.1 Float and Gray Outputs

8.2 Noise

8.3 Cellular

8.3.1 Tessellation

8.3.2 Worley

8.4 Spatial Warping

8.5 Fractals

8.5.1 Distortion

8.6 Ray Tracing

9. Signal Modification

9.1 Contrast

9.1.1 Average Value Interpolation

9.1.2 Range Remapping

9.1.3 Redistribution

9.2 Creasing

9.3 Skew

9.4 Range Clamping

9.5 Combining

9.5.1 Binary Operators

9.5.2 Weighted Mixing

9.5.3 Layering

9.5.4 Patterned Transitions

10. Displacement and Bumping

10.1 Common Space

10.2 Displacement

10.2.1 Height Patterns

10.2.2 Vector Patterns

10.2.3 Cascading Height Displacements

10.2.4 Geometry Inversion

10.3 Bumping

10.3.1 Vertex Shading Normals

10.3.2 BxDF Normal Orientation

10.3.3 Bump Conversion Shader

11. Shader Execution

11.1 JIT Optimization

11.2 Strings and Filenames

11.3 Displacement and BxDF Shading Phases

11.3.1 Micropolygon Dicing

11.3.2 Common Space

11.3.3 Surface Variables

11.3.4 "Original" Surface Variables

11.3.5 Ray Tracing

11.4 Differentiation

12. Interface Design

12.1 Naming

12.2 Metadata

12.3 Widgets

12.4 Types and Connections

12.5 Help Content

13. Development, Deployment, and Debugging

13.1 Source File Organization

13.2 Build System

13.3 Debugging

13.3.1 IT

13.3.2 printf()

13.3.3 The .rib File

Appendix

A. Pattern Dimension and the Fourier Slice Theorem

B. Fractal Dimension

C. Arbitrary Output Variables

D. Light Path Expressions

E. Build System

i. Top-level Makefile

ii. osl Makefile

iii. install_shaders.py