Initial version of MESA_texture_array spec.

1 files changed, 805 insertions, 0 deletions

diff --git a/docs/MESA_texture_array.spec b/docs/MESA_texture_array.spec
new file mode 100644
index 00000000000..d3b77521151
--- /dev/null
+++ b/docs/MESA_texture_array.spec
@@ -0,0 +1,805 @@
+Name
+
+    MESA_texture_array
+
+Name Strings
+
+    GL_MESA_texture_array
+
+Contact
+
+    Ian Romanick, IBM (idr 'at' us.ibm.com)
+
+IP Status
+
+    No known IP issues.
+
+Status
+
+    Shipping in Mesa 7.1
+
+Version
+
+    $Date: 2007/05/16$ $Revision: 0.4$
+
+Number
+
+    TBD
+
+Dependencies
+
+    OpenGL 1.2 or GL_EXT_texture3D is required.
+
+    Support for ARB_fragment_program is assumed, but not required.
+
+    Support for ARB_fragment_program_shadow is assumed, but not required.
+
+    Support for EXT_framebuffer_object is assumed, but not required.
+
+    Written based on the wording of the OpenGL 2.0 specification and
+    ARB_fragment_program_shadow but not dependent on them.
+
+Overview
+
+    There are a number of circumstances where an application may wish to
+    blend two textures out of a larger set of textures.  Moreover, in some
+    cases the selected textures may vary on a per-fragment basis within
+    a polygon.  Several examples include:
+
+       1. High dynamic range textures.  The application stores several
+       different "exposures" of an image as different textures.  On a
+       per-fragment basis, the application selects which exposures are
+       used.
+
+       2. A terrain engine where the altitude of a point determines the
+       texture applied to it.  If the transition is from beach sand to
+       grass to rocks to snow, the application will store each texture
+       in a different texture map, and dynamically select which two
+       textures to blend at run-time.
+
+       3. Storing short video clips in textures.  Each depth slice is a
+       single frame of video.
+
+    Several solutions to this problem have been proposed, but they either
+    involve using a separate texture unit for each texture map or using 3D
+    textures without mipmaps.  Both of these options have major drawbacks.
+
+    This extension provides a third alternative that eliminates the major
+    drawbacks of both previous methods.  A new texture target,
+    TEXTURE_2D_ARRAY, is added that functions identically to TEXTURE_3D in
+    all aspects except the sizes of the non-base level images.  In
+    traditional 3D texturing, the size of the N+1 LOD is half the size
+    of the N LOD in all three dimensions.  For the TEXTURE_2D_ARRAY target,
+    the height and width of the N+1 LOD is halved, but the depth is the
+    same for all levels of detail. The texture then becomes an array of
+    2D textures.  The per-fragment texel is selected by the R texture
+    coordinate.
+
+    References:
+
+        http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=011557
+        http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=000516
+        http://www.opengl.org/discussion_boards/cgi_directory/ultimatebb.cgi?ubb=get_topic;f=3;t=011903
+        http://www.delphi3d.net/articles/viewarticle.php?article=terraintex.htm
+
+New Procedures and Functions
+
+    All functions come directly from EXT_texture_array.
+
+    void FramebufferTextureLayerEXT(enum target, enum attachment,
+                                    uint texture, int level, int layer);
+
+New Tokens
+
+    All token names and values come directly from EXT_texture_array.
+
+    Accepted by the <cap> parameter of Enable, Disable, and IsEnabled, by
+    the <pname> parameter of GetBooleanv, GetIntegerv, GetFloatv, and
+    GetDoublev, and by the <target> parameter of TexImage3D, GetTexImage,
+    GetTexLevelParameteriv, GetTexLevelParameterfv, GetTexParameteriv, and
+    GetTexParameterfv:
+
+        TEXTURE_1D_ARRAY_EXT                            0x8C18
+        TEXTURE_2D_ARRAY_EXT                            0x8C1A
+
+    Accepted by the <target> parameter of TexImage2D, TexSubImage2D,
+    CopyTexImage2D, CopyTexSubImage2D, CompressedTexImage2D,
+    CompressedTexSubImage2D, GetTexLevelParameteriv, and 
+    GetTexLevelParameterfv:
+
+        TEXTURE_1D_ARRAY_EXT
+        PROXY_TEXTURE_1D_ARRAY_EXT                      0x8C19
+
+    Accepted by the <target> parameter of TexImage3D, TexSubImage3D,
+    CopyTexSubImage3D, CompressedTexImage3D, CompressedTexSubImage3D,
+    GetTexLevelParameteriv, and GetTexLevelParameterfv:
+
+        TEXTURE_2D_ARRAY_EXT
+        PROXY_TEXTURE_2D_ARRAY_EXT                      0x8C1B
+
+    Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
+    GetFloatv, and GetDoublev
+
+        TEXTURE_BINDING_1D_ARRAY_EXT                    0x8C1C
+        TEXTURE_BINDING_2D_ARRAY_EXT                    0x8C1D
+        MAX_ARRAY_TEXTURE_LAYERS_EXT                    0x88FF
+
+    Accepted by the <param> parameter of TexParameterf, TexParameteri,
+    TexParameterfv, and TexParameteriv when the <pname> parameter is
+    TEXTURE_COMPARE_MODE_ARB:
+
+        COMPARE_REF_DEPTH_TO_TEXTURE_EXT                0x884E
+
+    (Note:  COMPARE_REF_DEPTH_TO_TEXTURE_EXT is simply an alias for the
+    existing COMPARE_R_TO_TEXTURE token in OpenGL 2.0; the alternate name
+    reflects the fact that the R coordinate is not always used.)
+
+    Accepted by the <internalformat> parameter of TexImage3D and
+    CompressedTexImage3D, and by the <format> parameter of
+    CompressedTexSubImage3D:
+
+        COMPRESSED_RGB_S3TC_DXT1_EXT
+        COMPRESSED_RGBA_S3TC_DXT1_EXT
+        COMPRESSED_RGBA_S3TC_DXT3_EXT
+        COMPRESSED_RGBA_S3TC_DXT5_EXT
+
+    Accepted by the <pname> parameter of
+    GetFramebufferAttachmentParameterivEXT:
+
+        FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT          0x8CD4
+
+    (Note:  FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER is simply an alias for the
+    FRAMEBUFFER_ATTACHMENT_TEXTURE_3D_ZOFFSET_EXT token provided in
+    EXT_framebuffer_object.  This extension generalizes the notion of
+    "<zoffset>" to include layers of an array texture.)
+
+Additions to Chapter 2 of the OpenGL 2.0 Specification (OpenGL Operation)
+
+    None
+
+Additions to Chapter 3 of the OpenGL 2.0 Specification (Rasterization)
+
+    -- Section 3.8.1 "Texture Image Specification"
+
+       Change the first paragraph (page 150) to say (spec changes identical to
+       EXT_texture_array):
+
+       "The command
+
+         void TexImage3D(enum target, int level, int internalformat,
+                         sizei width, sizei height, sizei depth, int border,
+                         enum format, enum type, void *data);
+
+       is used to specify a three-dimensional texture image. target must be one
+       one of TEXTURE_3D for a three-dimensional texture or
+       TEXTURE_2D_ARRAY_EXT for an two-dimensional array texture.
+       Additionally, target may be either PROXY_TEXTURE_3D for a
+       three-dimensional proxy texture, or PROXY_TEXTURE_2D_ARRAY_EXT for a
+       two-dimensional proxy array texture."
+
+       Change the fourth paragraph on page 151 to say (spec changes identical
+       to EXT_texture_array):
+
+       "Textures with a base internal format of DEPTH_COMPONENT are supported
+       by texture image specification commands only if target is TEXTURE_1D,
+       TEXTURE_2D, TEXTURE_1D_ARRAY_EXT, TEXTURE_2D_ARRAY_EXT,
+       PROXY_TEXTURE_1D, PROXY_TEXTURE_2D, PROXY_TEXTURE_1D_ARRAY_EXT, or
+       PROXY_TEXTURE_2D_ARRAY_EXT. Using this format in conjunction with any
+       other target will result in an INVALID_OPERATION error."
+
+
+       Change the fourth paragraph on page 156 to say (spec changes identical
+       to EXT_texture_array):
+       
+       "The command
+
+         void TexImage2D(enum target, int level,
+                         int internalformat, sizei width, sizei height,
+                         int border, enum format, enum type, void *data);
+
+       is used to specify a two-dimensional texture image. target must be one
+       of TEXTURE_2D for a two-dimensional texture, TEXTURE_1D_ARRAY_EXT for a
+       one-dimensional array texture, or one of TEXTURE_CUBE_MAP_POSITIVE_X,
+       TEXTURE_CUBE_MAP_NEGATIVE_X, TEXTURE_CUBE_MAP_POSITIVE_Y,
+       TEXTURE_CUBE_MAP_NEGATIVE_Y, TEXTURE_CUBE_MAP_POSITIVE_Z, or
+       TEXTURE_CUBE_MAP_NEGATIVE_Z for a cube map texture. Additionally,
+       target may be either PROXY_TEXTURE_2D for a two-dimensional proxy
+       texture, PROXY_TEXTURE_1D_ARRAY_EXT for a one-dimensional proxy array
+       texture, or PROXY TEXTURE_CUBE_MAP for a cube map proxy texture in the
+       special case discussed in section 3.8.11.  The other parameters match
+       the corresponding parameters of TexImage3D.
+
+       For the purposes of decoding the texture image, TexImage2D is
+       equivalent to calling TexImage3D with corresponding arguments and depth
+       of 1, except that
+
+         * The border depth, d_b, is zero, and the depth of the image is
+           always 1 regardless of the value of border. 
+
+         * The border height, h_b, is zero if <target> is
+           TEXTURE_1D_ARRAY_EXT, and <border> otherwise.
+
+         * Convolution will be performed on the image (possibly changing its
+           width and height) if SEPARABLE 2D or CONVOLUTION 2D is enabled.
+
+         * UNPACK SKIP IMAGES is ignored."
+
+    -- Section 3.8.2 "Alternate Texture Image Specification Commands"
+
+       Change the second paragraph (page 159) (spec changes identical
+       to EXT_texture_array):
+
+       "The command
+
+         void CopyTexImage2D(enum target, int level,
+                             enum internalformat, int x, int y, sizei width,
+                             sizei height, int border);
+
+       defines a two-dimensional texture image in exactly the manner of
+       TexImage2D, except that the image data are taken from the framebuffer
+       rather than from client memory. Currently, target must be one of
+       TEXTURE_2D, TEXTURE_1D_ARRAY_EXT, TEXTURE_CUBE_MAP_POSITIVE_X,
+       TEXTURE_CUBE_MAP_NEGATIVE_X, TEXTURE_CUBE MAP_POSITIVE_Y,
+       TEXTURE_CUBE_MAP_NEGATIVE_Y, TEXTURE_CUBE_MAP_POSITIVE_Z, or
+       TEXTURE_CUBE_MAP_NEGATIVE_Z.
+
+
+       Change the last paragraph on page 160 to say (spec changes identical
+       to EXT_texture_array):
+
+       "Currently the target arguments of TexSubImage1D and CopyTexSubImage1D
+       must be TEXTURE_1D, the target arguments of TexSubImage2D and
+       CopyTexSubImage2D must be one of TEXTURE_2D, TEXTURE_1D_ARRAY_EXT,
+       TEXTURE_CUBE_MAP_POSITIVE_X, TEXTURE_CUBE_MAP_NEGATIVE_X,
+       TEXTURE_CUBE_MAP_POSITIVE_Y, TEXTURE_CUBE_MAP_NEGATIVE_Y,
+       TEXTURE_CUBE_MAP_POSITIVE_Z, or TEXTURE_CUBE_MAP_NEGATIVE_Z, and the
+       target arguments of TexSubImage3D and CopyTexSubImage3D must be
+       TEXTURE_3D or TEXTURE_2D_ARRAY_EXT. ..."
+
+
+    -- Section 3.8.4 "Texture Parameters"
+
+       Change the first paragraph (page 166) to say:
+
+       "Various parameters control how the texel array is treated when
+       specified or changed, and when applied to a fragment. Each parameter is
+       set by calling
+
+         void TexParameter{if}(enum target, enum pname, T param); 
+         void TexParameter{if}v(enum target, enum pname, T params);
+
+       target is the target, either TEXTURE_1D, TEXTURE_2D, TEXTURE_3D,
+       TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, or TEXTURE_2D_ARRAY_EXT."
+
+
+    -- Section 3.8.8 "Texture Minification" in the section "Scale Factor and Level of Detail"
+
+       Change the first paragraph (page 172) to say:
+
+       "Let s(x,y) be the function that associates an s texture coordinate
+       with each set of window coordinates (x,y) that lie within a primitive;
+       define t(x,y) and r(x,y) analogously.  Let u(x,y) = w_t * s(x,y),
+       v(x,y) = h_t * t(x,y), and w(x,y) = d_t * r(x,y), where w_t, h_t,
+       and d_t are as defined by equations 3.15, 3.16, and 3.17 with
+       w_s, h_s, and d_s equal to the width, height, and depth of the
+       image array whose level is level_base.  For a one-dimensional
+       texture or a one-dimensional array texture, define v(x,y) = 0 and
+       w(x,y) = 0; for a two-dimensional texture or a two-dimensional array
+       texture, define w(x,y) = 0..."
+
+    -- Section 3.8.8 "Texture Minification" in the section "Mipmapping"
+
+       Change the third paragraph (page 174) to say:
+       
+       "For a two-dimensional texture, two-dimensional array texture, or
+       cube map texture,"
+
+       Change the fourth paragraph (page 174) to say:
+
+       "And for a one-dimensional texture or a one-dimensional array texture,"
+
+       After the first paragraph (page 175) add:
+
+       "For one-dimensional array textures, h_b and d_b are treated as 1,
+       regardless of the actual values, when performing mipmap calculations.
+       For two-dimensional array textures, d_b is always treated as one,
+       regardless of the actual value, when performing mipmap calculations."
+
+    -- Section 3.8.8 "Automatic Mipmap Generation" in the section "Mipmapping"
+
+       Change the third paragraph (page 176) to say (spec changes identical
+       to EXT_texture_array):
+
+       "The contents of the derived arrays are computed by repeated, filtered
+       reduction of the level_base array.  For one- and two-dimensional array
+       textures, each layer is filtered independently.  ..."
+
+    -- Section 3.8.8 "Manual Mipmap Generation" in the section "Mipmapping"
+
+       Change first paragraph to say (spec changes identical to
+       EXT_texture_array):
+
+       "Mipmaps can be generated manually with the command
+
+         void GenerateMipmapEXT(enum target);
+
+       where <target> is one of TEXTURE_1D, TEXTURE_2D, TEXTURE_CUBE_MAP,
+       TEXTURE_3D, TEXTURE_1D_ARRAY, or TEXTURE_2D_ARRAY.  Mipmap generation
+       affects the texture image attached to <target>.  ..."
+
+    -- Section 3.8.10 "Texture Completeness"
+
+       Change the second paragaph (page 177) to say (spec changes identical
+       to EXT_texture_array):
+
+       "For one-, two-, or three-dimensional textures and one- or
+       two-dimensional array textures, a texture is complete if the following
+       conditions all hold true:"
+
+    -- Section 3.8.11 "Texture State and Proxy State"
+
+       Change the second and third paragraphs (page 179) to say (spec changes
+       identical to EXT_texture_array):
+
+       "In addition to image arrays for one-, two-, and three-dimensional
+       textures, one- and two-dimensional array textures, and the six image
+       arrays for the cube map texture, partially instantiated image arrays
+       are maintained for one-, two-, and three-dimensional textures and one-
+       and two-dimensional array textures.  Additionally, a single proxy image
+       array is maintained for the cube map texture.  Each proxy image array
+       includes width, height, depth, border width, and internal format state
+       values, as well as state for the red, green, blue, alpha, luminance,
+       and intensity component resolutions. Proxy image arrays do not include
+       image data, nor do they include texture properties. When TexImage3D is
+       executed with target specified as PROXY_TEXTURE_3D, the
+       three-dimensional proxy state values of the specified level-of-detail
+       are recomputed and updated. If the image array would not be supported
+       by TexImage3D called with target set to TEXTURE 3D, no error is
+       generated, but the proxy width, height, depth, border width, and
+       component resolutions are set to zero. If the image array would be
+       supported by such a call to TexImage3D, the proxy state values are set
+       exactly as though the actual image array were being specified. No pixel
+       data are transferred or processed in either case.
+
+       Proxy arrays for one- and two-dimensional textures and one- and
+       two-dimensional array textures are operated on in the same way when
+       TexImage1D is executed with target specified as PROXY_TEXTURE_1D,
+       TexImage2D is executed with target specified as PROXY_TEXTURE_2D or
+       PROXY_TEXTURE_1D_ARRAY_EXT, or TexImage3D is executed with target
+       specified as PROXY_TETXURE_2D_ARRAY_EXT."
+
+    -- Section 3.8.12 "Texture Objects"
+
+       Change section (page 180) to say (spec changes identical to 
+       EXT_texture_array):
+
+       "In addition to the default textures TEXTURE_1D, TEXTURE_2D,
+       TEXTURE_3D, TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, and TEXTURE_2D_EXT,
+       named one-, two-, and three-dimensional, cube map, and one- and
+       two-dimensional array texture objects can be created and operated upon.
+       The name space for texture objects is the unsigned integers, with zero
+       reserved by the GL.
+
+       A texture object is created by binding an unused name to TEXTURE_1D,
+       TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, or
+       TEXTURE_2D_ARRAY_EXT. The binding is effected by calling
+
+         void BindTexture(enum target, uint texture);
+
+       with <target> set to the desired texture target and <texture> set to
+       the unused name.  The resulting texture object is a new state vector,
+       comprising all the state values listed in section 3.8.11, set to the
+       same initial values. If the new texture object is bound to TEXTURE_1D,
+       TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, or
+       TEXTURE_2D_ARRAY_EXT, it is and remains a one-, two-,
+       three-dimensional, cube map, one- or two-dimensional array texture
+       respectively until it is deleted.
+
+       BindTexture may also be used to bind an existing texture object to
+       either TEXTURE_1D, TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP,
+       TEXTURE_1D_ARRAY_EXT, or TEXTURE_2D_ARRAY_EXT. The error
+       INVALID_OPERATION is generated if an attempt is made to bind a texture
+       object of different dimensionality than the specified target. If the
+       bind is successful no change is made to the state of the bound texture
+       object, and any previous binding to target is broken.
+
+       While a texture object is bound, GL operations on the target to which
+       it is bound affect the bound object, and queries of the target to which
+       it is bound return state from the bound object. If texture mapping of
+       the dimensionality of the target to which a texture object is bound is
+       enabled, the state of the bound texture object directs the texturing
+       operation.
+
+       In the initial state, TEXTURE_1D, TEXTURE_2D, TEXTURE_3D,
+       TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, and TEXTURE_2D_ARRAY_EXT have
+       one-, two-, three-dimensional, cube map, and one- and two-dimensional
+       array texture state vectors respectively associated with them. In order
+       that access to these initial textures not be lost, they are treated as
+       texture objects all of whose names are 0. The initial one-, two-,
+       three-dimensional, cube map, one- and two-dimensional array textures
+       are therefore operated upon, queried, and applied as TEXTURE_1D,
+       TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, and
+       TEXTURE_2D_ARRAY_EXT respectively while 0 is bound to the corresponding
+       targets.
+
+       Change second paragraph on page 181 to say (spec changes identical to 
+       EXT_texture_array):
+       
+       "...  If a texture that is currently bound to one of the targets
+       TEXTURE_1D, TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP,
+       TEXTURE_1D_ARRAY_EXT, or TEXTURE_2D_ARRAY_EXT is deleted, it is as
+       though BindTexture had been executed with the same target and texture
+       zero. ..."
+
+       Change second paragraph on page 182 to say (spec changes identical to 
+       EXT_texture_array):
+       
+       "The texture object name space, including the initial one-, two-, and
+       three dimensional, cube map, and one- and two-dimensional array texture
+       objects, is shared among all texture units. ..."
+
+
+    -- Section 3.8.14 "Depth Texture Comparison Modes" in "Texture Comparison Modes"
+
+       Change second through fourth paragraphs (page 188) to say:
+
+       "Let D_t be the depth texture value, in the range [0, 1].  For
+       texture lookups from one- and two-dimesional, rectangle, and
+       one-dimensional array targets, let R be the interpolated <r>
+       texture coordinate, clamped to the range [0, 1].  For texture lookups
+       from two-dimesional array texture targets, let R be the interpolated
+       <q> texture coordinate, clamped to the range [0, 1].  Then the
+       effective texture value L_t, I_t, or A_t is computed as follows:
+
+       If the value of TEXTURE_COMPARE_MODE is NONE, then
+
+          r = Dt
+
+       If the value of TEXTURE_COMPARE_MODE is
+       COMPARE_REF_DEPTH_TO_TEXTURE_EXT), then r depends on the texture
+       comparison function as shown in table 3.27."
+
+    -- Section 3.8.15 "Texture Application"
+
+       Change the first paragraph (page 189) to say:
+
+       "Texturing is enabled or disabled using the generic Enable and Disable
+       commands, respectively, with the symbolic constants TEXTURE_1D,
+       TEXTURE_2D, TEXTURE_3D, TEXTURE_CUBE_MAP, TEXTURE_1D_ARRAY_EXT, or
+       TEXTURE_2D_ARRAY_EXT to enable one-, two-, three-dimensional, cube
+       map, one-dimensional array, or two-dimensional array texture,
+       respectively.  If both two- and one-dimensional textures are enabled,
+       the two-dimensional texture is used.  If the three-dimensional and
+       either of the two- or one-dimensional textures is enabled, the
+       three-dimensional texture is used.  If the cube map texture and any of
+       the three-, two-, or one-dimensional textures is enabled, then cube map
+       texturing is used.  If one-dimensional array texture is enabled and any
+       of cube map, three-, two-, or one-dimensional textures is enabled, 
+       one-dimensional array texturing is used.  If two-dimensional array
+       texture is enabled and any of cube map, three-, two-, one-dimensional
+       textures or one-dimensional array texture is enabled, two-dimensional
+       array texturing is used..."
+
+    -- Section 3.11.2 of ARB_fragment_program (Fragment Program Grammar and Restrictions):
+
+       (mostly add to existing grammar rules)
+
+       <optionName>           ::= "MESA_texture_array"
+
+       <texTarget>            ::= "1D"
+                               | "2D"
+                               | "3D"
+                               | "CUBE"
+                               | "RECT"
+                               | <arrayTarget> (if program option is present)
+                               | <shadowTarget> (if program option is present)
+
+       <arrayTarget>          ::= "ARRAY1D"
+                               | "ARRAY2D"
+
+       <shadowTarget>         ::= "SHADOW1D"
+                               | "SHADOW2D"
+                               | "SHADOWRECT"
+                               | <shadowArrayTarget> (if program option is present)
+
+       <shadowArrayTarget>    ::= "SHADOWARRAY1D"
+                               | "SHADOWARRAY2D"
+
+
+    -- Add Section 3.11.4.5.4 "Texture Stack Option"
+
+       "If a fragment program specifies the "MESA_texture_array" program
+       option, the <texTarget> rule is modified to add the texture targets
+       ARRAY1D and ARRAY2D (See Section 3.11.2)."
+
+    -- Section 3.11.6 "Fragment Program Texture Instruction Set"
+
+       (replace 1st and 2nd paragraphs with the following paragraphs)
+
+       "The first three texture instructions described below specify the
+       mapping of 4-tuple input vectors to 4-tuple output vectors.
+       The sampling of the texture works as described in section 3.8,
+       except that texture environments and texture functions are not
+       applicable, and the texture enables hierarchy is replaced by explicit
+       references to the desired texture target (i.e., 1D, 2D, 3D, cube map,
+       rectangle, ARRAY1D, ARRAY2D).  These texture instructions specify
+       how the 4-tuple is mapped into the coordinates used for sampling.  The
+       following function is used to describe the texture sampling in the
+       descriptions below: 
+
+         vec4 TextureSample(vec4 coord, float lodBias, int texImageUnit,
+                            enum texTarget);
+
+       Note that not all four components of the texture coordinates <coord>
+       are used by all texture targets.  Component usage for each <texTarget>
+       is defined in table X.
+
+                                                        coordinates used
+         texTarget          Texture Type               s t r  layer  shadow
+         ----------------   ---------------------      -----  -----  ------
+         1D                 TEXTURE_1D                 x - -    -      -
+         2D                 TEXTURE_2D                 x y -    -      -
+         3D                 TEXTURE_3D                 x y z    -      -
+         CUBE               TEXTURE_CUBE_MAP           x y z    -      -
+         RECT               TEXTURE_RECTANGLE_ARB      x y -    -      -
+         ARRAY1D            TEXTURE_1D_ARRAY_EXT       x - -    y      -
+         ARRAY2D            TEXTURE_2D_ARRAY_EXT       x y -    z      -
+         SHADOW1D           TEXTURE_1D                 x - -    -      z
+         SHADOW2D           TEXTURE_2D                 x y -    -      z
+         SHADOWRECT         TEXTURE_RECTANGLE_ARB      x y -    -      z
+         SHADOWARRAY1D      TEXTURE_1D_ARRAY_EXT       x - -    y      z
+         SHADOWARRAY2D      TEXTURE_2D_ARRAY_EXT       x y -    z      w
+
+         Table X:  Texture types accessed for each of the <texTarget>, and
+         coordinate mappings.  The "coordinates used" column indicate the
+         input values used for each coordinate of the texture lookup, the
+         layer selector for array textures, and the reference value for
+         texture comparisons."
+
+    -- Section 3.11.6.2 "TXP: Project coordinate and map to color"
+    
+       Add to the end of the section:
+       
+       "A program will fail to load if the TXP instruction is used in
+       conjunction with the SHADOWARRAY2D target."
+
+Additions to Chapter 4 of the OpenGL 2.0 Specification (Per-Fragment Operations)
+
+    -- Section 4.4.2.3 "Attaching Texture Images to a Framebuffer"
+
+       Add to the end of the section (spec changes identical to
+       EXT_texture_array):
+
+       "The command
+
+         void FramebufferTextureLayerEXT(enum target, enum attachment,
+                                         uint texture, int level, int layer);
+
+       operates identically to FramebufferTexture3DEXT, except that it
+       attaches a single layer of a three-dimensional texture or a one- or
+       two-dimensional array texture.  <layer> is an integer indicating the
+       layer number, and is treated identically to the <zoffset> parameter in
+       FramebufferTexture3DEXT.  The error INVALID_VALUE is generated if
+       <layer> is negative.  The error INVALID_OPERATION is generated if
+       <texture> is non-zero and is not the name of a three dimensional
+       texture or one- or two-dimensional array texture.  Unlike
+       FramebufferTexture3D, no <textarget> parameter is accepted.
+
+       If <texture> is non-zero and the command does not result in an error,
+       the framebuffer attachment state corresponding to <attachment> is
+       updated as in the other FramebufferTexture commands, except that
+       FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT is set to <layer>."
+
+    -- Section 4.4.4.1 "Framebuffer Attachment Completeness"
+
+      Add to the end of the list of completeness rules (spec changes
+      identical to EXT_texture_array):
+
+        "* If FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE_EXT is TEXTURE and
+           FRAMEBUFFER_ATTACHMENT_OBJECT_NAME_EXT names a one- or 
+           two-dimensional array texture, then
+           FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT must be smaller than the
+           number of layers in the texture."
+
+Additions to Chapter 5 of the OpenGL 2.0 Specification (Special Functions)
+
+    -- Section 5.4 "Display Lists"
+
+       Change the first paragraphi on page 242 to say (spec changes
+       identical to EXT_texture_array):
+
+       "TexImage3D, TexImage2D, TexImage1D, Histogram, and ColorTable are
+       executed immediately when called with the corresponding proxy arguments
+       PROXY_TEXTURE_3D or PROXY_TEXTURE_2D_ARRAY_EXT; PROXY_TEXTURE_2D,
+       PROXY_TEXTURE_CUBE_MAP, or PROXY_TEXTURE_1D_ARRAY_EXT;
+       PROXY_TEXTURE_1D; PROXY_HISTOGRAM; and PROXY_COLOR_TABLE,
+       PROXY_POST_CONVOLUTION_COLOR_TABLE, or
+       PROXY_POST_COLOR_MATRIX_COLOR_TABLE."
+
+Additions to Chapter 6 of the OpenGL 2.0 Specification (State and State Requests)
+
+    -- Section 6.1.3 "Enumerated Queries"
+
+       Add after the line beginning "If the value of
+       FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE_EXT is TEXTURE" (spec changes
+       identical to EXT_texture_array):
+
+       "If <pname> is FRAMEBUFFER_ATTACHMENT_TEXTURE_LAYER_EXT and the
+       texture object named FRAMEBUFFER_ATTACHMENT_OBJECT_NAME_EXT is a
+       three-dimensional texture or a one- or two-dimensional array texture,
+       then <params> will contain the number of texture layer attached to the
+       attachment point.  Otherwise, <params> will contain the value zero."
+
+    -- Section 6.1.4 "Texture Queries"
+    
+       Change the first three paragraphs (page 248) to say (spec changes
+       identical to EXT_texture_array):
+
+       "The command
+
+         void GetTexImage(enum tex, int lod, enum format,
+                          enum type, void *img);
+
+       is used to obtain texture images. It is somewhat different from the
+       other get commands; tex is a symbolic value indicating which texture
+       (or texture face in the case of a cube map texture target name) is to
+       be obtained.  TEXTURE_1D, TEXTURE_2D, TEXTURE_3D, TEXTURE_1D_ARRAY_EXT,
+       and TEXTURE_2D_ARRAY_EXT indicate a one-, two-, or three-dimensional
+       texture, or one- or two-dimensional array texture, respectively.
+       TEXTURE_CUBE_MAP_POSITIVE_X, ...
+
+       GetTexImage obtains... from the first image to the last for
+       three-dimensional textures.  One- and two-dimensional array textures
+       are treated as two- and three-dimensional images, respectively, where
+       the layers are treated as rows or images.  These groups are then...
+
+       For three-dimensional and two-dimensional array textures, pixel storage
+       operations are applied as if the image were two-dimensional, except
+       that the additional pixel storage state values PACK_IMAGE_HEIGHT and
+       PACK_SKIP_IMAGES are applied. ..."
+
+Additions to Appendix A of the OpenGL 2.0 Specification (Invariance)
+
+    None
+
+Additions to the AGL/GLX/WGL Specifications
+
+    None
+
+GLX Protocol
+
+    None
+
+Dependencies on ARB_fragment_program
+
+    If ARB_fragment_program is not supported, the changes to section 3.11
+    should be ignored.
+
+Dependencies on EXT_framebuffer_object
+
+    If EXT_framebuffer_object is not supported, the changes to section
+    3.8.8 ("Manual Mipmap Generation"), 4.4.2.3, and 6.1.3 should be ignored.
+
+Dependencies on EXT_texture_compression_s3tc and NV_texture_compression_vtc
+
+    (Identical dependency as EXT_texture_array.)
+
+    S3TC texture compression is supported for two-dimensional array textures.
+    When <target> is TEXTURE_2D_ARRAY_EXT, each layer is stored independently
+    as a compressed two-dimensional textures.  When specifying or querying
+    compressed images using one of the S3TC formats, the images are provided
+    and/or returned as a series of two-dimensional textures stored
+    consecutively in memory, with the layer closest to zero specified first.
+    For array textures, images are not arranged in 4x4x4 or 4x4x2 blocks as in
+    the three-dimensional compression format provided in the
+    EXT_texture_compression_vtc extension.  Pixel store parameters, including
+    those specific to three-dimensional images, are ignored when compressed
+    image data are provided or returned, as in the
+    EXT_texture_compression_s3tc extension.
+
+    S3TC compression is not supported for one-dimensional texture targets in
+    EXT_texture_compression_s3tc, and is not supported for one-dimensional
+    array textures in this extension.  If compressed one-dimensional arrays
+    are needed, use a two-dimensional texture with a height of one.
+
+    This extension allows the use of the four S3TC internal format types in
+    TexImage3D, CompressedTexImage3D, and CompressedTexSubImage3D calls.
+
+Errors
+
+    None
+
+New State
+
+    (add to table 6.15, p. 276)
+
+                                                     Initial
+    Get Value                     Type   Get Command  Value Description           Sec.    Attribute
+    ----------------------------  -----  -----------  ----- --------------------  ------  ---------
+    TEXTURE_BINDING_1D_ARRAY_EXT  2*xZ+  GetIntegerv    0   texture object bound  3.8.12  texture
+                                                            to TEXTURE_1D_ARRAY
+    TEXTURE_BINDING_2D_ARRAY_EXT  2*xZ+  GetIntegerv    0   texture object bound  3.8.12  texture
+                                                            to TEXTURE_2D_ARRAY
+
+
+New Implementation Dependent State
+
+    (add to Table 6.32, p. 293)
+
+                                                    Minimum
+    Get Value                     Type  Get Command  Value  Description         Sec.  Attribute
+    ----------------------------  ----  ----------- ------- ------------------  ----- ---------
+    MAX_TEXTURE_ARRAY_LAYERS_EXT   Z+   GetIntegerv   64    maximum number of   3.8.1     -
+                                                            layers for texture
+                                                            arrays
+
+Issues
+
+    (1) Is "texture stack" a good name for this functionality?
+
+        NO.  The name is changed to "array texture" to match the
+        nomenclature used by GL_EXT_texture_array.
+
+    (2) Should the R texture coordinate be treated as normalized or
+    un-normalized?  If it were un-normalized, floor(R) could be thought
+    of as a direct index into the array texture.  This may be more
+    convenient for applications.
+
+        RESOLVED.  All texture coordinates are normalized.  The issue of
+        un-normalized texture coordinates has been discussed in the ARB
+        before and should be left for a layered extension.
+
+        RE-RESOLVED.  The R coordinate is un-normalized.  Accessing an array
+        using [0, layers-1] coordinates is much more natural.
+
+    (3) How does LOD selection work for stacked textures?
+
+        RESOLVED.  For 2D array textures the R coordinate is ignored, and
+        the LOD selection equations for 2D textures are used.  For 1D
+        array textures the T coordinate is ignored, and the LOD selection
+        equations for 1D textures are used.  The expected usage is in a
+        fragment program with an explicit LOD selection.
+
+    (4) What is the maximum size of a 2D array texture?  Is it the same
+    as for a 3D texture, or should a new query be added?  How about for 1D
+    array textures?
+
+        RESOLVED.  A new query is added.
+
+    (5) How are array textures exposed in GLSL?
+    
+        RESOLVED.  Use GL_EXT_texture_array.
+        
+    (6) Should a 1D array texture also be exposed?
+
+        RESOLVED.  For orthogonality, yes.
+
+    (7) How are stacked textures attached to framebuffer objects?
+
+        RESOLVED.  Layers of both one- and two-dimensional array textures
+        are attached using FreambufferTextureLayerEXT.  Once attached, the
+        array texture layer behaves exactly as either a one- or
+        two-dimensional texture.
+
+    (8) How is this extension related to GL_EXT_texture_array?
+    
+        This extension adapats GL_MESAX_texture_stack to the notation,
+        indexing, and FBO access of GL_EXT_texture_array.  This extension
+        replaces the GLSL support of GL_EXT_texture_array with
+        GL_ARB_fragment_program support.
+
+        Assembly program support is also provided by GL_NV_gpu_program4.
+        GL_NV_gpu_program4 also adds support for other features that are
+        specific to Nvidia hardware, while this extension adds only support
+        for array textures.
+
+        Much of text of this extension that has changed since
+        GL_MESAX_texture_stack comes directly from either
+        GL_EXT_texture_array or GL_NV_gpu_program4.
+
+Revision History
+
+    ||2005/11/15||0.1||idr||Initial draft MESAX version.||
+    ||2005/12/07||0.2||idr||Added framebuffer object interactions.||
+    ||2005/12/12||0.3||idr||Updated fragment program interactions.||
+    ||2007/05/16||0.4||idr||Converted to MESA_texture_array.  Brought in line with EXT_texture_array and NV_gpu_program4.||