The OpenGL
®
ES Shading Language
Language Version: 1.00
Document Revision: 17
12 May, 2009
Editor: Robert J. Simpson
(Editor, version 1.00, revisions 1-11: John Kessenich)
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Copyright (c) 2006-2009 The Khronos Group Inc. All Rights Reserved.
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Version 1.00 Revision 17 (12 May, 2009)
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Table of Contents
1 Introduction................................................................................................................................1
1.1 Change History...................................................................................................................1
1.2 Overview............................................................................................................................6
1.3 Error Handling....................................................................................................................6
1.4 Typographical Conventions...............................................................................................7
2 Overview of OpenGL ES Shading.............................................................................................8
2.1 Vertex Processor................................................................................................................8
2.2 Fragment Processor............................................................................................................8
3 Basics.........................................................................................................................................9
3.1 Character Set......................................................................................................................9
3.2 Source Strings....................................................................................................................9
3.3 Logical Phases of compilation.........................................................................................10
3.4 Preprocessor.....................................................................................................................11
3.5 Comments........................................................................................................................15
3.6 Tokens..............................................................................................................................16
3.7 Keywords..........................................................................................................................16
3.8 Identifiers.........................................................................................................................17
4 Variables and Types.................................................................................................................18
4.1 Basic Types......................................................................................................................18
4.1.1 Void..........................................................................................................................19
4.1.2 Booleans...................................................................................................................19
4.1.3 Integers.....................................................................................................................19
4.1.4 Floats........................................................................................................................21
4.1.5 Vectors......................................................................................................................21
4.1.6 Matrices....................................................................................................................22
4.1.7 Samplers...................................................................................................................22
4.1.8 Structures..................................................................................................................22
4.1.9 Arrays.......................................................................................................................24
4.2 Scoping.............................................................................................................................25
4.2.1 Definition of Terms..................................................................................................25
4.2.2 Types of Scope.........................................................................................................25
4.2.3 Redeclaring Variables...............................................................................................26
4.2.4 Shared Globals..........................................................................................................26
4.2.5 Global Scope............................................................................................................27
4.2.6 Name spaces and Hiding..........................................................................................27
4.2.7 Redeclarations and Redefinitions Within the Same Scope......................................27
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4.3 Storage Qualifiers.............................................................................................................29
4.3.1 Default Storage Qualifier..........................................................................................29
4.3.2 Constant Qualifier....................................................................................................29
4.3.3 Attribute....................................................................................................................30
4.3.4 Uniform....................................................................................................................30
4.3.5 Varying.....................................................................................................................31
4.4 Parameter Qualifiers.........................................................................................................32
4.5 Precision and Precision Qualifiers...................................................................................32
4.5.1 Range and Precision.................................................................................................32
4.5.2 Precision Qualifiers..................................................................................................33
4.5.3 Default Precision Qualifiers.....................................................................................35
4.5.4 Available Precision Qualifiers..................................................................................36
4.6 Variance and the Invariant Qualifier................................................................................36
4.6.1 The Invariant Qualifier.............................................................................................37
4.6.2 Invariance Within Shaders........................................................................................38
4.6.3 Invariance of Constant Expressions.........................................................................39
4.6.4 Invariance and Linkage.............................................................................................39
4.7 Order of Qualification......................................................................................................39
5 Operators and Expressions.......................................................................................................40
5.1 Operators..........................................................................................................................40
5.2 Array Subscripting...........................................................................................................41
5.3 Function Calls..................................................................................................................41
5.4 Constructors.....................................................................................................................41
5.4.1 Conversion and Scalar Constructors........................................................................41
5.4.2 Vector and Matrix Constructors...............................................................................42
5.4.3 Structure Constructors..............................................................................................43
5.5 Vector Components..........................................................................................................44
5.6 Matrix Components..........................................................................................................45
5.7 Structures and Fields........................................................................................................46
5.8 Assignments.....................................................................................................................46
5.9 Expressions......................................................................................................................47
5.10 Constant Expressions.....................................................................................................49
5.11 Vector and Matrix Operations........................................................................................50
5.12 Precisions of operations.................................................................................................51
5.13 Evaluation of expressions..............................................................................................51
6 Statements and Structure..........................................................................................................52
6.1 Function Definitions.........................................................................................................53
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6.1.1 Function Calling Conventions..................................................................................54
6.2 Selection...........................................................................................................................56
6.3 Iteration............................................................................................................................56
6.4 Jumps................................................................................................................................57
7 Built-in Variables.....................................................................................................................59
7.1 Vertex Shader Special Variables......................................................................................59
7.2 Fragment Shader Special Variables.................................................................................60
7.3 Vertex Shader Built-In Attributes....................................................................................61
7.4 Built-In Constants............................................................................................................61
7.5 Built-In Uniform State.....................................................................................................62
8 Built-in Functions....................................................................................................................63
8.1 Angle and Trigonometry Functions..................................................................................64
8.2 Exponential Functions......................................................................................................65
8.3 Common Functions..........................................................................................................66
8.4 Geometric Functions........................................................................................................68
8.5 Matrix Functions..............................................................................................................69
8.6 Vector Relational Functions.............................................................................................70
8.7 Texture Lookup Functions...............................................................................................71
9 Shading Language Grammar....................................................................................................73
10 Issues......................................................................................................................................84
10.1 Vertex Shader Precision.................................................................................................84
10.2 Fragment Shader Precision.............................................................................................84
10.3 Precision Qualifiers........................................................................................................84
10.4 Function and Variable Name Spaces..............................................................................88
10.5 Local Function Declarations and Function Hiding........................................................88
10.6 Overloading main()........................................................................................................88
10.7 Error Reporting..............................................................................................................88
10.8 Structure Declarations....................................................................................................89
10.9 Embedded Structure Definitions....................................................................................89
10.10 Redefining Built-in Functions......................................................................................90
10.11 Constant Expressions...................................................................................................90
10.12 Varying Linkage...........................................................................................................91
10.13 gl_Position....................................................................................................................91
10.14 Pre-processor................................................................................................................91
10.15 Phases of Compilation..................................................................................................92
10.16 Maximum Number of Varyings...................................................................................92
10.17 Unsized Array Declarations.........................................................................................93
Version 1.00 Revision 17 (12 May, 2009)
