Name 

    EXT_gpu_program_parameters 

Name Strings 

    GL_EXT_gpu_program_parameters 

Contributors

    Pat Brown
    Haroon Sheikh
   
Contact 

    Pat Brown, NVIDIA Corporation (pbrown 'at' nvidia.com) 
    Geoff Stahl, Apple Computer, Inc. (gstahl 'at' apple.com)

Status 

    Shipping for GeForce 8 Series (November 2006) 

Version 

    Last Modified Date:         4/17/08
    Revision:                   7

Number 

    320 

Dependencies 

    ARB_vertex_program or ARB_fragment_program is required. 

    This specification is written against the spec language from the 
    ARB_vertex_program extension. 

Overview 

    This extension provides a new set of procedures to load multiple 
    consecutive program environment parameters more efficiently, via a single 
    GL call instead of multiple calls.  This will reduce the amount of CPU 
    overhead involved in loading parameters. 

    With the existing ARB_vertex_program and ARB_fragment_program APIs, 
    program parameters must be loaded one at a time, via separate calls. 
    While the NV_vertex_program extension provides a set of similar functions 
    that can be used to load program environment parameters (which are 
    equivalent to "program parameters" in NV_vertex_program), no such function 
    exists for program local parameters. 

New Procedures and Functions 

    void ProgramEnvParameters4fvEXT(enum target, uint index, sizei count, 
                                   const float *params); 

    void ProgramLocalParameters4fvEXT(enum target, uint index, sizei count, 
                                     const float *params); 

New Tokens 
    
    None. 

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

    (modify ARB_vertex_program and ARB_fragment_program, add paragraph after
    introduction of ProgramEnvParameter* calls) 

    The command 

      void ProgramEnvParameters4fvEXT(enum target, uint index, sizei count, 
                                      const float *params); 

    updates the values of the program environment parameters numbered <index>
    through <index> + <count> - 1 for the given program target <target>.
    <params> points to an array of 4*<count> values, where the first four are
    used to update the program environment parameter numbered <index> and the
    last four update the program environment parameter numbered <index> +
    <count> - 1.  The error INVALID_VALUE is generated if <count> is less than
    zero or if the sum of <index> and <count> is greater than the number of
    program environment parameters supported by <target>.

    (modify ARB_vertex_program and ARB_fragment_program, add paragraph after
    introduction of ProgramLocalParameter* calls) 

    The command 

      void ProgramLocalParameters4fvEXT(enum target, uint index, sizei count, 
                                        const float *params); 

    updates the values of the program local parameters numbered <index>
    through <index> + <count> - 1 belonging to the program object currently
    bound to <target>.  <params> points to an array of 4*<count> values, where
    the first four are used to update the program local parameter numbered
    <index> and the last four update the program local parameter numbered
    <index> + <count> - 1.  The error INVALID_VALUE is generated if <count> is
    less than zero or if the sum of <index> and <count> is greater than the
    number of program local parameters supported by <target>.

Additions to Chapter 3 of the OpenGL 2.0 Specification (Rasterization) 

    None. 

Additions to Chapter 4 of the OpenGL 2.0 Specification (Per-Fragment 
Operations and the Frame Buffer) 

    None. 

Additions to Chapter 5 of the OpenGL 2.0 Specification (Special Functions) 

    None. 

Additions to Chapter 6 of the OpenGL 2.0 Specification (State and 
State Requests) 

    None. 

Additions to Appendix A of the OpenGL 2.0 Specification (Invariance) 

    None. 

Additions to the AGL/GLX/WGL Specifications 

    None. 

GLX Protocol 

    Two new GL commands are added.  The following commands are sent to the
    server as part of a glXRender request:

        ProgramEnvParameters4fvEXT 
            2           16+16*n         rendering command length 
            2           4281            rendering command opcode 
            4           ENUM            target 
            4           CARD32          index 
            4           CARD32          n 
            16*n        FLOAT32         params 

        ProgramLocalParameters4fvEXT 
            2           16+16*n         rendering command length 
            2           4282            rendering command opcode 
            4           ENUM            target 
            4           CARD32          index 
            4           CARD32          n 
            16*n        FLOAT32         params 

Errors 

    INVALID_VALUE is generated by ProgramEnvParameters4fvEXT or
    ProgramLocalParameters4fvEXT if <count> is less than zero.

    INVALID_VALUE is generated by ProgramEnvParameters4fvEXT if <index> plus
    <count> is greater than the number of program environment parameters
    supported by <target>.

    INVALID_VALUE is generated by ProgramLocalParameters4fvEXT if <index> plus
    <count> is greater than the number of program local parameters supported
    by <target>.

New State 

    None. 

Issues 

    (1) Should a set of ProgramEnvParameters*EXT() calls be added, or is using 
        NV_vertex_program's ProgramParameters*NV() sufficient? 

      RESOLVED:  We should add an ARB-style ProgramEnvParameters*() call for 
      naming consistency. Also ProgramParameters*NV() are not available on 
      all platforms.

    (2) Should an equivalent set of calls be added to query multiple program 
        parameters at once? 

      RESOLVED:  No. 

    (3) Should double-precision versions be supported? 

      RESOLVED:  No.  Double-precision parameter values will be converted to 
      single-precision in current driver implementations, anyway. 

    (4) Why is this spec called "EXT_gpu_program_parameters"?

      RESOLVED:  The functionality provided by this spec applies to more than
      one program type.  The term "GPU" was used in the extension name to
      indicate functionality common to all supported program types, which are
      commonly executed on a GPU.

    (5) Is it an error to load multiple parameters with a <count> of zero?

      RESOLVED:  No.  However, it was illegal in versions of the spec prior to
      9/27/07.  The spec was changed to resolve differences between the
      shipping implementations from NVIDIA (which did enforce the error) and
      Apple (which did not).  The new behavior is more consistent with the
      standard OpenGL practice of allowing zero to be passed to GLsizei
      parameters, and avoids the need for special-case behavior to
      handle/avoid zero counts in both drivers and applications.  Since
      loading zero program parameters has no actual effect, the only
      difference between the two behaviors is the update of the GL error
      state.


Revision History 

    Rev.    Date    Author    Changes 
    ----  --------  --------  -------------------------------------------- 
    7     04/17/08  pbrown    Fix GLX protocol section to indicate two
                              functions instead of four.

    6     09/27/07  pbrown    Change the spec to indicate that it's not
                              illegal to load zero parameters, just
                              pointless.

    5     11/06/06  mjk       Indicate shipping

    4     06/28/06  barthold  Make clear that this spec modifies both
                              ARB_vertex_program and ARB_fragment_program.

    3     06/27/06  pbrown    Fix incorrect error language in checking the
                              sum of <index> and <count>, added an issue
                              about the spec name.

    2     06/02/06  haroon    Changed to EXT. Added contributors.

    1     04/24/06  pbrown    Initial revision.