GL_ARB_transpose_matrix |

- Name
- Name Strings
- Contact
- Status
- Version
- Number
- Dependencies
- Overview
- IP Status
- Issues
- New Procedures and Functions
- New Tokens
- Additions to Chapter 2 of the 1.2 OpenGL Specification (OpenGL Operation)
- Additions to Chapter 3 of the 1.2 OpenGL Specification (Rasterization)
- Additions to Chapter 4 of the 1.2 OpenGL Specification (Per-Fragment Operations and the Framebuffer)
- Additions to Chapter 5 of the 1.2 OpenGL Specification (Special Functions)
- Additions to Chapter 6 of the 1.2 OpenGL Specification (State and State Requests)
- Additions to Appendix A of the OpenGL 1.2.1 Specification (Invariance)
- Additions to the GLX Specification
- GLX Protocol
- Errors
- New State
- New Implementation Dependent State
- Revision History

Name |

ARB_transpose_matrix

Name Strings |

GL_ARB_transpose_matrix

Contact |

David Blythe (blythe 'at' sgi.com)

Status |

Complete. Approved by ARB on 12/8/1999

Version |

Last Modified Date: January 3, 2000 Author Revision: 1.3

Number |

ARB Extension #3

Dependencies |

This extensions is written against the OpenGL 1.2 Specification. May be implemented in any version of OpenGL.

Overview |

New functions and tokens are added allowing application matrices stored in row major order rather than column major order to be transferred to the OpenGL implementation. This allows an application to use standard C-language 2-dimensional arrays (m[row][col]) and have the array indices match the expected matrix row and column indexes. These arrays are referred to as transpose matrices since they are the transpose of the standard matrices passed to OpenGL. This extension adds an interface for transfering data to and from the OpenGL pipeline, it does not change any OpenGL processing or imply any changes in state representation.

IP Status |

No IP is believed to be involved.

Issues |

* Why do this? It's very useful for layered libraries that desire to use two dimensional C arrays as matrices. It avoids having the layered library perform the transpose itself before calling OpenGL since most OpenGL implementations can efficiently perform the transpose while reading the matrix from client memory. * Why not add a mode? It's substantially more confusing and complicated to add a mode. Simply adding two new entry points saves considerable confusion and avoids having layered libraries need to query the current mode in order to send a matrix with the correct memory layout. * Why not a utility routine in GLU It costs some performance. It is believed that most OpenGL implementations can perform the transpose in place with negligble performance penalty. * Why use the name transpose? It's sure a lot less confusing than trying to ascribe unambiguous meaning to terms like row and column. It could be matrix_transpose rather than transpose_matrix though. * Short Transpose to Trans?

New Procedures and Functions |

void LoadTransposeMatrix{fd}ARB(T m[16]); void MultTransposeMatrix{fd}ARB(T m[16]);

New Tokens |

Accepted by the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev TRANSPOSE_MODELVIEW_MATRIX_ARB 0x84E3 TRANSPOSE_PROJECTION_MATRIX_ARB 0x84E4 TRANSPOSE_TEXTURE_MATRIX_ARB 0x84E5 TRANSPOSE_COLOR_MATRIX_ARB 0x84E6

Additions to Chapter 2 of the 1.2 OpenGL Specification (OpenGL Operation) |

Add to Section 2.10.2 Matrices <before LoadIdentity> LoadTransposeMatrixARB takes a 4x4 matrix stored in row-major order as Let transpose(m,n) be defined as n[0] = m[0]; n[1] = m[4]; n[2] = m[8]; n[3] = m[12]; n[4] = m[1]; n[5] = m[5]; n[6] = m[9]; n[7] = m[13]; n[8] = m[2]; n[9] = m[6]; n[10] = m[10]; n[11] = m[14]; n[12] = m[3]; n[13] = m[7]; n[14] = m[11]; n[15] = m[15]; The effect of LoadTransposeMatrixARB(m) is then the same as the effect of the command sequence float n[16]; transpose(m,n) LoadMatrix(n); The effect of MultTransposeMatrixARB(m) is then the same as the effect of the command sequence float n[16]; transpose(m,n); MultMatrix(n);

Additions to Chapter 3 of the 1.2 OpenGL Specification (Rasterization) |

None

Additions to Chapter 4 of the 1.2 OpenGL Specification (Per-Fragment Operations and the Framebuffer) |

None

Additions to Chapter 5 of the 1.2 OpenGL Specification (Special Functions) |

None

Additions to Chapter 6 of the 1.2 OpenGL Specification (State and State Requests) |

Matrices are queried and returned in their transposed form by calling GetBooleanv, GetIntegerv, GetFloatv, and GetDoublev with <pname> set to TRANSPOSE_MODELVIEW_MATRIX_ARB, TRANSPOSE_PROJECTION_MATRIX_ARB, TRANSPOSE_TEXTURE_MATRIX_ARB, or TRANSPOSE_COLOR_MATRIX_ARB. The effect of GetFloatv(TRANSPOSE_MODELVIEW_MATRIX_ARB,m) is then the same as the effect of the command sequence float n[16]; GetFloatv(MODELVIEW_MATRIX_ARB,n); transpose(n,m); Similar results occur for TRANSPOSE_PROJECTION_MATRIX_ARB, TRANSPOSE_TEXTURE_MATRIX_ARB, and TRANSPOSE_COLOR_MATRIX_ARB.

Additions to Appendix A of the OpenGL 1.2.1 Specification (Invariance) |

None

Additions to the GLX Specification |

None

GLX Protocol |

LoadTransposeMatrix and MultTransposeMatrix are layered on top of LoadMatrix and MultMatrix protocol performing client-side translation. The Get commands are passed over the wire as part of the generic Get protocol with no translation required.

Errors |

No new errors, but error behavoir is inherited by the commands that the transpose commands are implemented on top of (LoadMatrix, MultMatrix, and Get*).

New State |

None TRANSPOSE_*_MATRIX_ARB refer to the same state as their non-transposed counterparts.

New Implementation Dependent State |

None

Revision History |

* Revision 1.1 - initial draft (18 Mar 1999) * Revision 1.2 - changed to use layered specification and ARB affix (23 Nov 1999) * Revision 1.3 - Minor tweaks to GLX protocol and Errors. (7 Dec 1999) Conformance Testing Load and Multiply the modelview matrix (initialized to identity each time) using LoadTransposeMatrixfARB and MultTransposeMatrixfARB with the matrix: ( 1 2 3 4 ) ( 5 6 7 8 ) ( 9 10 11 12 ) (13 14 15 16 ) and get the modelview matrix using TRANSPOSE_MODELVIEW_MATRIX_ARB and validate that the matrix is correct. Get the matrix using MODELVIEW_MATRIX and verify that it is the transpose of the above matrix. Load and Multiply the modelview matrix using LoadMatrixf and MultMatrixf with the above matrix and verify that the correct matrix is on the modelview stack using gets of MODELVIEW_MATRIX and TRANSPOSE_MODELVIEW_MATRIX_ARB.

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