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
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 paragraph (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-dimensional, 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-dimensional 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 paragraph 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.||