The OpenGL R Graphics System: A Specification (Version 3.3 (Core Profile) - March 11, 2010) Mark Segal Kurt Akeley Editor (version 1.1): Chris Frazier Editor (versions 1.2-3.3): Jon Leech Editor (version 2.0): Pat Brown Copyright c 2006-2010 The Khronos Group Inc. All Rights Reserved. This specification is protected by copyright laws and contains material proprietary to the Khronos Group, Inc. It or any components may not be reproduced, repub- lished, distributed, transmitted, displayed, broadcast or otherwise exploited in any manner without the express prior written permission of Khronos Group. You may use this specification for implementing the functionality therein, without altering or removing any trademark, copyright or other notice from the specification, but the receipt or possession of this specification does not convey any rights to reproduce, disclose, or distribute its contents, or to manufacture, use, or sell anything that it may describe, in whole or in part. 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Contents 1 Introduction1 1.1 Formatting of the OpenGL Specification . .1 1.2 What is the OpenGL Graphics System? . .1 1.3 Programmer’s View of OpenGL . .1 1.4 Implementor’s View of OpenGL . .2 1.5 Our View . .2 1.6 The Deprecation Model . .3 1.7 Companion Documents . .3 1.7.1 OpenGL Shading Language . .3 1.7.2 Window System Bindings . .3 2 OpenGL Operation5 2.1 OpenGL Fundamentals . .5 2.1.1 Floating-Point Computation . .7 2.1.2 16-Bit Floating-Point Numbers . .8 2.1.3 Unsigned 11-Bit Floating-Point Numbers . .8 2.1.4 Unsigned 10-Bit Floating-Point Numbers . .9 2.1.5 Fixed-Point Data Conversions . 10 2.2 GL State . 12 2.2.1 Shared Object State . 13 2.3 GL Command Syntax . 13 2.4 Basic GL Operation . 15 2.5 GL Errors . 18 2.6 Primitives and Vertices . 19 2.6.1 Primitive Types . 21 2.7 Vertex Specification . 26 2.8 Vertex Arrays . 28 2.8.1 Transferring Array Elements . 31 2.8.2 Packed Vertex Data Formats . 32 i CONTENTS ii 2.8.3 Drawing Commands . 32 2.9 Buffer Objects . 37 2.9.1 Creating and Binding Buffer Objects . 38 2.9.2 Creating Buffer Object Data Stores . 40 2.9.3 Mapping and Unmapping Buffer Data . 42 2.9.4 Effects of Accessing Outside Buffer Bounds . 47 2.9.5 Copying Between Buffers . 47 2.9.6 Vertex Arrays in Buffer Objects . 48 2.9.7 Array Indices in Buffer Objects . 48 2.9.8 Buffer Object State . 49 2.10 Vertex Array Objects . 49 2.11 Vertex Shaders . 50 2.11.1 Shader Objects . 51 2.11.2 Program Objects . 52 2.11.3 Vertex Attributes . 55 2.11.4 Uniform Variables . 58 2.11.5 Samplers . 74 2.11.6 Varying Variables . 75 2.11.7 Shader Execution . 77 2.11.8 Required State . 83 2.12 Geometry Shaders . 84 2.12.1 Geometry Shader Input Primitives . 85 2.12.2 Geometry Shader Output Primitives . 86 2.12.3 Geometry Shader Variables . 87 2.12.4 Geometry Shader Execution Environment . 88 2.13 Coordinate Transformations . 92 2.13.1 Controlling the Viewport . 92 2.14 Asynchronous Queries . 93 2.15 Conditional Rendering . 95 2.16 Transform Feedback . 96 2.17 Primitive Queries . 99 2.18 Flatshading . 100 2.19 Primitive Clipping . 100 2.19.1 Clipping Shader Varying Outputs . 103 3 Rasterization 104 3.1 Discarding Primitives Before Rasterization . 105 3.2 Invariance . 105 3.3 Antialiasing . 106 3.3.1 Multisampling . 107 OpenGL 3.3 (Core Profile) - March 11, 2010 CONTENTS iii 3.4 Points . 109 3.4.1 Basic Point Rasterization . 110 3.4.2 Point Rasterization State . 110 3.4.3 Point Multisample Rasterization . 111 3.5 Line Segments . 111 3.5.1 Basic Line Segment Rasterization . 111 3.5.2 Other Line Segment Features . 114 3.5.3 Line Rasterization State . 114 3.5.4 Line Multisample Rasterization . 114 3.6 Polygons . 115 3.6.1 Basic Polygon Rasterization . 116 3.6.2 Antialiasing . 118 3.6.3 Options Controlling Polygon Rasterization . 118 3.6.4 Depth Offset . 119 3.6.5 Polygon Multisample Rasterization . 120 3.6.6 Polygon Rasterization State . 121 3.7 Pixel Rectangles . 121 3.7.1 Pixel Storage Modes and Pixel Buffer Objects . 121 3.7.2 Transfer of Pixel Rectangles . 122 3.8 Texturing . 134 3.8.1 Texture Objects . 135 3.8.2 Sampler Objects . 137 3.8.3 Texture Image Specification . 139 3.8.4 Alternate Texture Image Specification Commands . 151 3.8.5 Compressed Texture Images . 158 3.8.6 Multisample Textures . 162 3.8.7 Buffer Textures . 163 3.8.8 Texture Parameters . 166 3.8.9 Depth Component Textures . 168 3.8.10 Cube Map Texture Selection . 168 3.8.11 Texture Minification . 170 3.8.12 Texture Magnification . 179 3.8.13 Combined Depth/Stencil Textures . 179 3.8.14 Texture Completeness . 179 3.8.15 Texture State and Proxy State . 181 3.8.16 Texture Comparison Modes . 183 3.8.17 sRGB Texture Color Conversion . 183 3.8.18 Shared Exponent Texture Color Conversion . 184 3.9 Fragment Shaders . 185 3.9.1 Shader Variables . 185 OpenGL 3.3 (Core Profile) - March 11, 2010 CONTENTS iv 3.9.2 Shader Execution . 186 3.10 Antialiasing Application . 192 3.11 Multisample Point Fade . 192 4 Per-Fragment Operations and the Framebuffer 193 4.1 Per-Fragment Operations . 194 4.1.1 Pixel Ownership Test . 195 4.1.2 Scissor Test . 195 4.1.3 Multisample Fragment Operations . 196 4.1.4 Stencil Test . 198 4.1.5 Depth Buffer Test . 199 4.1.6 Occlusion Queries . 200 4.1.7 Blending . 201 4.1.8 sRGB Conversion . 207 4.1.9 Dithering . 207 4.1.10 Logical Operation . 208 4.1.11 Additional Multisample Fragment Operations . 209 4.2 Whole Framebuffer Operations . 210 4.2.1 Selecting a Buffer for Writing . 210 4.2.2 Fine Control of Buffer Updates . 214 4.2.3 Clearing the Buffers . 216 4.3 Reading and Copying Pixels . 218 4.3.1 Reading Pixels . 218 4.3.2 Copying Pixels . 225 4.3.3 Pixel Draw/Read State . 228 4.4 Framebuffer Objects . 228 4.4.1 Binding and Managing Framebuffer Objects . 228 4.4.2 Attaching Images to Framebuffer Objects . 231 4.4.3 Feedback Loops Between Textures and the Framebuffer . 239 4.4.4.