extensions/OES/OES_texture_npot.txt - external/github.com/KhronosGroup/OpenGL-Registry - Git at Google

 Name

     OES_texture_npot

 Name Strings

     GL_OES_texture_npot

 Contact

     Bruce Merry (bruce.merry at arm.com)

 Contributors

     Khronos OpenGL ES working group
     Contributors to ARB_texture_non_power_of_two

 Notice

     Copyright (c) 2005-2013 The Khronos Group Inc. Copyright terms at
         http://www.khronos.org/registry/speccopyright.html

 Specification Update Policy

     Khronos-approved extension specifications are updated in response to
     issues and bugs prioritized by the Khronos OpenGL Working Group. For
     extensions which have been promoted to a core Specification, fixes will
     first appear in the latest version of that core Specification, and will
     eventually be backported to the extension document. This policy is
     described in more detail at
         https://www.khronos.org/registry/OpenGL/docs/update_policy.php

 IP Status

     None.

 Status

     Ratified by the Khronos BOP, July 22, 2005.

 Version

     Last Modifed Date: 2011-03-07
     Author Revision: 3

 Number

     OpenGL ES Extension #37

 Dependencies

     OpenGL ES 1.0 or OpenGL ES 2.0 is required. This extension is
     written against OpenGL ES 1.1.12 and OpenGL ES 2.0.25.

     This extension interacts with OES_framebuffer_object, OES_texture_3D
     and APPLE_texture_2D_limited_npot.

 Overview

     This extension adds support for the REPEAT and MIRRORED_REPEAT
     texture wrap modes and the minification filters supported for
     non-power of two 2D textures, cubemaps and for 3D textures, if
     the OES_texture_3D extension is supported.

     Section 3.8.2 of the OpenGL ES 2.0 specification describes
     rules for sampling from an incomplete texture. There were specific
     rules added for non-power of two textures i.e. if the texture wrap
     mode is not CLAMP_TO_EDGE or minification filter is not NEAREST or
     LINEAR and the texture is a non-power-of-two texture, then sampling
     the texture will return (0, 0, 0, 1).

     These rules are no longer applied by an implementation that supports
     this extension.

 Additions to Chapter 3 of the OpenGL ES 2.0 Full Specification

     In section 3.7.1 (Texture Image Specification), remove the sentence

         "If <level> is greater than zero, and either <width> or <height>
         is not a power of two, the error INVALID_VALUE is generated."

     In section 3.7.7 (Texture Minification), remove the paragraph

         "If any dimension of any array in a mipmap is not a power of two
         (e.g. if rounding down as described above is performed), then
         the mipmap is described as a non-power-of-two texture.
         Non-power-of-two textures have restrictions on the allowed
         texture wrap modes and filters, as described in section 3.8.2."

     Change the title of 3.7.10 (Texture Completeness and
     Non-Power-Of-Two Textures) to "Texture Completeness".

     In section 3.7.11 (Mipmap Generation), remove the sentence

         "If either the width or height of the level zero array are not a
         power or two, the error INVALID_OPERATION is generated."

     In section 3.8.2 (Shader Execution), remove the bullet points

         "
         - A two-dimensional sampler is called, the corresponding texture
           image is a non-power-of-two image (as described in the
           Mipmapping discussion of section 3.7.7), and either the
           texture wrap mode is not CLAMP_TO_EDGE, or the minification
           filter is neither NEAREST nor LINEAR.

         - A cube map sampler is called, any of the corresponding texture
           images are non-power-of-two images, and either the texture
           wrap mode is not CLAMP_TO_EDGE, or the minification filter
           is neither NEAREST nor LINEAR.
         "

 Additions to Chapter 3 of the OpenGL ES 1.1.12 Full Specification

     In section 3.7.1 (Texture Image Specification):

     Replace the discussion of valid dimensions with

     "If w_s and h_s are the specified image width and height, and if w_s
     or h_s is less than zero, then the error INVALID_VALUE is
     generated."

     Replace the discussion of image decoding with:

     "We shall refer to the decoded image as the texture array.  A
     texture array has width and height w_s and h_s as defined above."

     Update Figure 3.8's caption:

     "... This is a texture with w_t = 8 and h_t = 4.  ..."


     In section 3.7.7 (Texture Minification):

     In the subsection "Scale Factor and Level of Detail"...

     Replace the sentence defining the u and v functions with:

     "Let u(x,y) = w_s * s(x,y) and v(x,y) = h_s * t(x,y), where w_s and
     h_s are equal to the width and height of the image array whose level
     is zero."

     Replace 2^n and 2^m with w_s and h_s in Equations 3.16 and 3.17.

           { floor(u),   s < 1
       i = {                              (3.16)
           { w_s - 1,    s = 1

           { floor(v),   t < 1
       j = {                              (3.17)
           { h_s - 1,    t = 1

     Replace 2^n and 2^m with w_s and h_s in the equations for computing i_0,
     j_0, i_1, and j_1 used for LINEAR filtering.

             { floor(u - 1/2) mod w_s,   TEXTURE_WRAP_S is REPEAT
       i_0 = {
             { floor(u - 1/2),           otherwise

             { floor(v - 1/2) mod h_s,   TEXTURE_WRAP_T is REPEAT
       j_0 = {
             { floor(v - 1/2),           otherwise

             { (i_0 + 1) mod w_s,        TEXTURE_WRAP_S is REPEAT
       i_1 = {
             { i_0 + 1,                  otherwise

             { (j_0 + 1) mod h_s,        TEXTURE_WRAP_T is REPEAT
       j_1 = {
             { j_0 + 1,                  otherwise

     In the subsection "Mipmapping", replace the description of the
     number of sizes of image arrays with

     "If the image array of level zero has dimensions w_t x h_t, then
     there are floor(log2(max(w_t, h_t))) + 1 image arrays in the mipmap.
     Each array subsequent to the level zero array has dimensions

         max(1, floor(w_t/2^i)) x max(1, floor(h_t/2^i))

     until the last array is reached with dimension 1 x 1.

 Interactions with OES_framebuffer_object

     If OES_framebuffer_object is supported, then GenerateMipmapOES does
     not generate an error if the base level is a non-power-of-two image.

 Interactions with OES_texture_3D

     If OES_texture_3D is supported, references to width and height
     should be extended to refer to depth as appropriate, and mipmap
     generation is permitted for non-power-of-two 3D textures.

 Interactions with APPLE_texture_2D_limited_npot

     This extension is a superset of the function in
     APPLE_texture_2D_limited_npot. Implementations may choose to
     advertise both extensions, but APPLE_texture_2D_limited_npot is not
     required to implement this extension on OpenGL ES 1.x.

 Issues

     1) How does this extension interact with manual mipmap generation
     (GenerateMipmap and GenerateMipmapOES)?

     RESOLVED: These are supported for NPOT textures.

     The initial version of this extension did not remove the error when
     issuing these commands on an non-power-of-two texture, but multiple
     vendors implemented support for it anyway.

     2) How does this extension interact with automatic mipmap generation
     in GL ES 1.1 (GENERATE_MIPMAP)?

     RESOLVED: These are supported for NPOT textures.

     3) How should this extension interact with
     APPLE_texture_2D_limited_npot?

     RESOLVED: it will be a superset, but will not require it.

     4) How should this extension interact with OES_texture_3D?

     RESOLVED: mipmap generation of NPOT 3D textures is supported.

     OES_texture_3D already specifies that OES_texture_npot enables
     support for mipmapped 3D textures, but it is unclear whether this
     should also allow mipmap generation for NPOT 3D textures.

     5) How should this extension interact with
     OES_compressed_paletted_texture?

     UNRESOLVED

     Specifically, it's now possible for a row of texels to not be a
     multiple of the unit size (bytes for PALETTE4_xxx, 32-bit words for
     PALETTE8_xxx). Options seem to be

     A) Pad each row to a multiple of the unit size.
     B) Pad each image to a multiple of the unit size.
     C) No padding - images can start in the middle of a unit.

 New Tokens

     None.

 New Procedures and Functions

     None.

 Errors

     None.

 New State

     None.

 Revision History

     3       2011-03-07  Bruce Merry      Added issue 5

     2       2011-03-01  Bruce Merry      Filled in body and issues

     1       2005-07-06  Aaftab Munshi    Created the extension
	Name

	OES_texture_npot

	Name Strings

	GL_OES_texture_npot

	Contact

	Bruce Merry (bruce.merry at arm.com)

	Contributors

	Khronos OpenGL ES working group
	Contributors to ARB_texture_non_power_of_two

	Notice

	Copyright (c) 2005-2013 The Khronos Group Inc. Copyright terms at
	http://www.khronos.org/registry/speccopyright.html

	Specification Update Policy

	Khronos-approved extension specifications are updated in response to
	issues and bugs prioritized by the Khronos OpenGL Working Group. For
	extensions which have been promoted to a core Specification, fixes will
	first appear in the latest version of that core Specification, and will
	eventually be backported to the extension document. This policy is
	described in more detail at
	https://www.khronos.org/registry/OpenGL/docs/update_policy.php

	IP Status

	None.

	Status

	Ratified by the Khronos BOP, July 22, 2005.

	Version

	Last Modifed Date: 2011-03-07
	Author Revision: 3

	Number

	OpenGL ES Extension #37

	Dependencies

	OpenGL ES 1.0 or OpenGL ES 2.0 is required. This extension is
	written against OpenGL ES 1.1.12 and OpenGL ES 2.0.25.

	This extension interacts with OES_framebuffer_object, OES_texture_3D
	and APPLE_texture_2D_limited_npot.

	Overview

	This extension adds support for the REPEAT and MIRRORED_REPEAT
	texture wrap modes and the minification filters supported for
	non-power of two 2D textures, cubemaps and for 3D textures, if
	the OES_texture_3D extension is supported.

	Section 3.8.2 of the OpenGL ES 2.0 specification describes
	rules for sampling from an incomplete texture. There were specific
	rules added for non-power of two textures i.e. if the texture wrap
	mode is not CLAMP_TO_EDGE or minification filter is not NEAREST or
	LINEAR and the texture is a non-power-of-two texture, then sampling
	the texture will return (0, 0, 0, 1).

	These rules are no longer applied by an implementation that supports
	this extension.

	Additions to Chapter 3 of the OpenGL ES 2.0 Full Specification

	In section 3.7.1 (Texture Image Specification), remove the sentence

	"If <level> is greater than zero, and either <width> or <height>
	is not a power of two, the error INVALID_VALUE is generated."

	In section 3.7.7 (Texture Minification), remove the paragraph

	"If any dimension of any array in a mipmap is not a power of two
	(e.g. if rounding down as described above is performed), then
	the mipmap is described as a non-power-of-two texture.
	Non-power-of-two textures have restrictions on the allowed
	texture wrap modes and filters, as described in section 3.8.2."

	Change the title of 3.7.10 (Texture Completeness and
	Non-Power-Of-Two Textures) to "Texture Completeness".

	In section 3.7.11 (Mipmap Generation), remove the sentence

	"If either the width or height of the level zero array are not a
	power or two, the error INVALID_OPERATION is generated."

	In section 3.8.2 (Shader Execution), remove the bullet points

	"
	- A two-dimensional sampler is called, the corresponding texture
	image is a non-power-of-two image (as described in the
	Mipmapping discussion of section 3.7.7), and either the
	texture wrap mode is not CLAMP_TO_EDGE, or the minification
	filter is neither NEAREST nor LINEAR.

	- A cube map sampler is called, any of the corresponding texture
	images are non-power-of-two images, and either the texture
	wrap mode is not CLAMP_TO_EDGE, or the minification filter
	is neither NEAREST nor LINEAR.
	"

	Additions to Chapter 3 of the OpenGL ES 1.1.12 Full Specification

	In section 3.7.1 (Texture Image Specification):

	Replace the discussion of valid dimensions with

	"If w_s and h_s are the specified image width and height, and if w_s
	or h_s is less than zero, then the error INVALID_VALUE is
	generated."

	Replace the discussion of image decoding with:

	"We shall refer to the decoded image as the texture array. A
	texture array has width and height w_s and h_s as defined above."

	Update Figure 3.8's caption:

	"... This is a texture with w_t = 8 and h_t = 4. ..."


	In section 3.7.7 (Texture Minification):

	In the subsection "Scale Factor and Level of Detail"...

	Replace the sentence defining the u and v functions with:

	"Let u(x,y) = w_s * s(x,y) and v(x,y) = h_s * t(x,y), where w_s and
	h_s are equal to the width and height of the image array whose level
	is zero."

	Replace 2^n and 2^m with w_s and h_s in Equations 3.16 and 3.17.

	{ floor(u), s < 1
	i = { (3.16)
	{ w_s - 1, s = 1

	{ floor(v), t < 1
	j = { (3.17)
	{ h_s - 1, t = 1

	Replace 2^n and 2^m with w_s and h_s in the equations for computing i_0,
	j_0, i_1, and j_1 used for LINEAR filtering.

	{ floor(u - 1/2) mod w_s, TEXTURE_WRAP_S is REPEAT
	i_0 = {
	{ floor(u - 1/2), otherwise

	{ floor(v - 1/2) mod h_s, TEXTURE_WRAP_T is REPEAT
	j_0 = {
	{ floor(v - 1/2), otherwise

	{ (i_0 + 1) mod w_s, TEXTURE_WRAP_S is REPEAT
	i_1 = {
	{ i_0 + 1, otherwise

	{ (j_0 + 1) mod h_s, TEXTURE_WRAP_T is REPEAT
	j_1 = {
	{ j_0 + 1, otherwise

	In the subsection "Mipmapping", replace the description of the
	number of sizes of image arrays with

	"If the image array of level zero has dimensions w_t x h_t, then
	there are floor(log2(max(w_t, h_t))) + 1 image arrays in the mipmap.
	Each array subsequent to the level zero array has dimensions

	max(1, floor(w_t/2^i)) x max(1, floor(h_t/2^i))

	until the last array is reached with dimension 1 x 1.

	Interactions with OES_framebuffer_object

	If OES_framebuffer_object is supported, then GenerateMipmapOES does
	not generate an error if the base level is a non-power-of-two image.

	Interactions with OES_texture_3D

	If OES_texture_3D is supported, references to width and height
	should be extended to refer to depth as appropriate, and mipmap
	generation is permitted for non-power-of-two 3D textures.

	Interactions with APPLE_texture_2D_limited_npot

	This extension is a superset of the function in
	APPLE_texture_2D_limited_npot. Implementations may choose to
	advertise both extensions, but APPLE_texture_2D_limited_npot is not
	required to implement this extension on OpenGL ES 1.x.

	Issues

	1) How does this extension interact with manual mipmap generation
	(GenerateMipmap and GenerateMipmapOES)?

	RESOLVED: These are supported for NPOT textures.

	The initial version of this extension did not remove the error when
	issuing these commands on an non-power-of-two texture, but multiple
	vendors implemented support for it anyway.

	2) How does this extension interact with automatic mipmap generation
	in GL ES 1.1 (GENERATE_MIPMAP)?

	RESOLVED: These are supported for NPOT textures.

	3) How should this extension interact with
	APPLE_texture_2D_limited_npot?

	RESOLVED: it will be a superset, but will not require it.

	4) How should this extension interact with OES_texture_3D?

	RESOLVED: mipmap generation of NPOT 3D textures is supported.

	OES_texture_3D already specifies that OES_texture_npot enables
	support for mipmapped 3D textures, but it is unclear whether this
	should also allow mipmap generation for NPOT 3D textures.

	5) How should this extension interact with
	OES_compressed_paletted_texture?

	UNRESOLVED

	Specifically, it's now possible for a row of texels to not be a
	multiple of the unit size (bytes for PALETTE4_xxx, 32-bit words for
	PALETTE8_xxx). Options seem to be

	A) Pad each row to a multiple of the unit size.
	B) Pad each image to a multiple of the unit size.
	C) No padding - images can start in the middle of a unit.

	New Tokens

	None.

	New Procedures and Functions

	None.

	Errors

	None.

	New State

	None.

	Revision History

	3 2011-03-07 Bruce Merry Added issue 5

	2 2011-03-01 Bruce Merry Filled in body and issues

	1 2005-07-06 Aaftab Munshi Created the extension