Name

    ATI_vertex_streams

Name Strings

    GL_ATI_vertex_streams

Contact

    Benj Lipchak, AMD (benj.lipchak 'at' amd.com)
    Evan Hart, NVIDIA (ehart 'at' nvidia.com)

Version

    Date: 11/4/2006
    Revision: 0.31

Number

    249

Dependencies

    OpenGL 1.0 is required.
    ARB_vertex_blend is required.
    This extension is written against the OpenGL 1.2.1 Specification.

Overview

    This extension adds the ability to handle sets of auxilliary
    vertex and normal coordinates. These sets of auxilliary
    coordinates are termed streams, and can be routed selectively
    into the blend stages provided by the vertex blending extension.
    This functionality enables software animation techniques such
    as keyframe vertex morphing.

    
IP Status

    Unknown, but believed to be none. 

Issues

     
New Procedures and Functions

    void VertexStream{1234}{sifd}(enum stream, T coords)
    void VertexStream{1234}{sifd}v(enum stream, T coords)

    void NormalStream3{bsifd}(enum stream, T coords)
    void NormalStream3{bsifd}v(enum stream, T coords)

    void ClientActiveVertexStream(enum stream)

    void VertexBlendEnv{if}(enum pname, T param)

New Tokens

    Accepted by the <pname> parameters of GetIntegerv, GetFloatv, and
    GetDoublev:

      MAX_VERTEX_STREAMS_ATI           0x876B

    Accepted by the <stream> parameters of VertexStream and
    ClientActiveVertexStream:

      VERTEX_STREAM0_ATI:              0x876C
      VERTEX_STREAM1_ATI:              0x876D
      VERTEX_STREAM2_ATI:              0x876E
      VERTEX_STREAM3_ATI:              0x876F
      VERTEX_STREAM4_ATI:              0x8770
      VERTEX_STREAM5_ATI:              0x8771
      VERTEX_STREAM6_ATI:              0x8772
      VERTEX_STREAM7_ATI:              0x8773


    Accepted by the <pname> parameter of VertexBlendEnv:

      VERTEX_SOURCE_ATI:               0x8774


Additions to Chapter 2 of the OpenGL 1.2.1 Specification (Operation)

    - (2.6, p. 12) Second paragraph changed to:

          "Each vertex is specified with two, three, or four
          coordinates. In addition, current auxilliary vertices, 
          a current normal, auxilliary normals, current texture
          coordinates, and current color may be used in processing
          each vertex. Normals are used by the GL in lighting
          calculations; the current normals are three-dimensional
          vectors that may be set by sending three coordinates that
          specify them. Texture coordinates determine how a texture
          image is mapped onto a primitive."

    - (2.6, p. 12) Added after the second paragraph:

          "Each auxilliary set of vertex and normal coordinates
          is refered to as a vertex stream. The vertex coordinate and
          normal for a vertex are the 0th stream, and each auxilliary
          set rpovided by the implementation after that is refered to
          as the ith stream. The number of streams supported by an
          implementation is return by Get when the pname parameter is
          MAX_VERTEX_STREAMS_ATI."

    - (2.6.3, p. 19) First paragraph changed to:

          "The only GL commands that are allowed within any Begin/End
          pairs are the commands for specifying vertex coordinates,
          auxilliary vertex coordinates, vertex color, normal
          coordinates, auxilliary normal coordinates, and texture
          coordinates (Vertex, VertexStream, Color, Index, Normal,
          NormalStream, TexCoord), the ArrayElement command (see
          section 2.8), the EvalCoord and EvalPoint commands (see
          section 5.1), commands for specifying lighting material
          parameters (Material commands; see section 2.13.2), display
          list invocation commands (CallList and CallLists; see
          section 5.4), and the EdgeFlag command. Executing any other
          GL command between the execution of a Begin and the
          corresponding execution of End results in the error
          INVALID_OPERATION. Executing Begin after Begin has already
          been executed but before an End is executed generates the
          INVALID_OPERATION error, as does executing End without
          a previous corresponding Begin."

    - (2.7, p. 20) Added after the first paragraph:

          "Alternatively, vertices and auxilliary vertices can be
          specified with the commands

              void VertexStream{234}{sifd}(enum stream, T coords)
              void VertexStream{234}{sifd}v(enum stream, T coords)

          These commands operate identically the the corresponding
          Vertex commands, but they may specify which stream the
          vertex data is to be placed in. If the stream parameter
          specifies a stream greater than the one minus the maximum
          number of streams reported by Get, then the error
          INVALID_ENUM is generated."

    - (2.7, p. 20) Added after the third paragraph:

          "The normals and auxilliary normals may also be specified
          with the commands

              void NormalStream3{bsifd}(enum stream, T coords)
              void NormalStream3{bsifd}v(enum stream, T coords)

          These commands operate identically to the corresponding
          Normal commands, but they allow the specification of which
          vertex stream the normal is to be used with. If the stream
          parameter is VERTEX_STREAM0_ATI, then this is the default
          current normal. Otherwise, it is one of the auxilliary
          normals. If the stream parameter specifies a stream greater
          than one minus the maximum number reported by Get, then
          the error INVALID_ENUM is generated."

    - (2.8, p. 23) Added after the second paragraph:

          "Additionally, auxillary vertex and normal data can be 
          specified through the VertexPointer and NormalPointer
          commands. Whether these commands are affecting the primary
          coordinates or the auxilliary coordinates is controlled by
          the command:

            void ClientActiveVertexStream(enum stream)

          This sets the current client vertex stream, so that all
          following VertexPointer and NormalPointer commands
          affect that client stream. If ClientActiveVertexStream
          is called with a stream greater than is reported as being
          supported by get, then the error INVALID_ENUM is
          generated."

    - (2.10, p. 29) Added after the first paragraph:

          "When vertex blending is enabled, and the vertex is
          being transformed by multiple modelview matrices,
          the auxiliary sets of vertex and normal data my be
          supplied to a vertex unit to be transformed. Each
          vertex unit transforms its currently selected stream.
          The active vertex stream for a vertex unit is specified
          by the command:

            void VertexBlendEnv{if}(enum pname, T param)

          This command changes the active vertex stream for the
          currently selected vertex stage. Param must be less than
          the maximum number of streams reported by get. The 
          select the current vertex stage to effect is done by
          calling MatrixMode with MODELVIEWn_ARB, where n is
          the vertex stage." 


Additions to Chapter 3:

      None

Additions to Chapter 4:

      None

Additions to Chapter 5:

      Open issue with evaluators

Additions to Chapter 6:

      Rather obvious changes to Get

Additions to Appendix A:

      None