Name

    OES_vertex_type_10_10_10_2

Name Strings

    GL_OES_vertex_type_10_10_10_2

Contributors

    Daniel Ginsburg
    Gary King
    Petri Kero
    Aaftab Munshi
    Acorn Pooley
    Mark Callow
    Ben Bowman

Contact

    Aaftab Munshi (amunshi@apple.com)

Notice

    Copyright (c) 2006-2013 The Khronos Group Inc. Copyright terms at
        http://www.khronos.org/registry/speccopyright.html

IP Status

    None.

Status

    Ratified by the Khronos BOP, March 20, 2008.

Version

    Last Modified Date: July 17, 2007

Number

    OpenGL ES Extension #46

Dependencies

    This extension is written against the OpenGL ES 2.0 specification

Overview

    This extension adds the following data formats:
    
    Two new vertex attribute data formats: a signed 10.10.10.2 and an unsigned 
    10.10.10.2 vertex data format.  These vertex data formats describe a 3- or 4-tuple 
    stream which can be used to store normals or other attributes in a quantized
    form.  Normals, tangents, binormals and other vertex attributes can often be specified 
    at reduced precision without introducing noticeable artifacts, reducing the 
    amount of memory and memory bandwidth they consume.

Issues

    1.  Should VertexAttrib{1234}[v] functions take UNSIGNED_INT_10_10_10_2_OES and 
        INT_10_10_10_2_OES data formats?

    RESOLUTION: No.  
    
    There is no reason to support this, as these functions are not performance or memory 
    footprint critical.  It is much more important that the vertex data specified using 
    vertex arrays be able to support these new formats.  In addition, we would need a 
    new data type suffix (similar to "f" for float, "x" for fixed) to denote these two
    new data types which is not desirable.

    2.  Should unsigned 10.10.10.2 RGBA and unsigned 10.10.10 RGB texture formats be
        supported by this extension?

    RESOLUTION: No.

    This extension should focus on enabling 10.10.10{.2} vertex data formats.  
    The 10.10.10{.2} texture formats should be a separate extension.


New Procedures and Functions

    None

New Tokens

    Accepted by the <type> parameter of VertexAttribPointer

        UNSIGNED_INT_10_10_10_2_OES                 0x8DF6
        INT_10_10_10_2_OES                          0x8DF7

Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL Operation)

    Modifications to section 2.8 (Vertex Arrays)

        Add INT_10_10_10_2_OES and UNSIGNED_INT_10_10_10_2_OES as a valid <type> value in Table 2.4.
        
    Add a new section 2.8.1 - UNSIGNED_INT_10_10_10_2_OES and INT_10_10_10_2_OES vertex data formats  

        UNSIGNED_INT_10_10_10_2_OES and INT_10_10_10_2_OES vertex data formats describe packed
        3- or 4- component formats stored in a 32-bit word.  These components are expanded to 
        (x, y, z, 1.0) if <size> = 3, or (x, y, z, w) if <size> = 4.
    
        For UNSIGNED_INT_10_10_10_2_OES vertex data format, the x, y and z components are 
        represented as a 10-bit unsigned integer value and the w component is represented as a 
        2-bit unsigned integer value.
        
        For INT_10_10_10_2_OES vertex data format, the x, y and z components are represented 
        as a 10-bit signed two's complement integer value and the w component is represented 
        as a 2-bit signed two's complement integer value.  
        
        The <normalized> value is used to indicate whether to normalize the data to 
        [0, 1] (for unsigned type) or [-1, 1] (for signed type).

        The following figure describes how these components are laid out in a 32-bit word.

  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
  -------------------------------------------------------------------------------------
 |            x                |                y            |          z          | w |                   
  -------------------------------------------------------------------------------------

        Calls to VertexAttribPointer with <type> of INT_10_10_10_2_OES and 
        UNSIGNED_INT_10_10_10_2_OES  can only be made with <size> = 3 or 4.  
        <size> values other than 3 or 4 will return an INVALID_VALUE error.  


    Modifications to table 2.9 (Component conversions)

        Add the following entries:

            GLType                     Conversion of (x, y, z)  Conversion of w
            -------                    ----------------------   ===============
            INT_10_10_10_2_OES        (2c + 1)/(2^10 - 1)       (2c + 1)/(2^2 - 1)
            UNSIGNED_10_10_10_2_OES    c / (2^10 - 1)            c / (2^2 - 1)

Errors

    The error INVALID_VALUE is generated if glVertexAttribPointer is called
    with <type> = UNSIGNED_INT_10_10_10_2_OES or INT_10_10_10_2_OES and the
    <size> parameter is not set to 3 or 4.

New State

    None

Revision History

    March 2, 2006    Aaftab Munshi    First draft of extension.

    March 3, 2006    Aaftab Munshi    Changed DEC3N, UDEC3N to INT_10_10_10_2
                                      and UNSIGNED_INT_10_10_10_2 resp.
                                      use <normalize> parameter to mark
                                      whether data is to be normalized or not.

                                      Changed extension name to GL_ATI_vertex_type_10_10_10_2

                                      Changed error returned from INVALID_ENUM
                                      to INVALID_VALUE if <size> != 3

    March 3, 2006    Aaftab Munshi    Added Contributors section.

    April 10,2006    Aaftab Munshi    Support for *_10_10_10_2 as a texture format

    June  3, 2006    Aaftab Munshi    Renamed to use OES suffixes.

    June 14, 2006    Aaftab Munshi    Allow 10_10_10_2 to be (x,y,z,1) or (x,y,z,w)
                                      when used as a vertex attribute data format.

    Oct  20, 2006    Aaftab Munshi    Fixed errors to say 3- or 4- tuples instead
                                          of just 3- tuples.

    Jun  13, 2007    Aaftab Munshi    Removed 10.10.10{.2} texture formats.

    Jul  10, 2007    Aaftab Munshi    Clarified that each component is a signed 2's complement
                                      integer or unsigned integer value.
                                      Shorten the extension name from OES_vertex_data_type_10_10_10_2.

    Jul  17, 2007    Aaftab Munshi    Corrections to section 2.8