--- /dev/null
+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.||
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