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kc3-lang/angle/extensions/EXT_texture_storage.txt
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- extensions/EXT_texture_storage.txt
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Name EXT_texture_storage Name Strings GL_EXT_texture_storage Contact Bruce Merry (bmerry 'at' gmail.com) Ian Romanick, Intel (ian.d.romanick 'at' intel.com) Contributors Jeremy Sandmel, Apple Bruce Merry, ARM Tom Olson, ARM Benji Bowman, Imagination Technologies Ian Romanick, Intel Jeff Bolz, NVIDIA Pat Brown, NVIDIA Maurice Ribble, Qualcomm Lingjun Chen, Qualcomm Daniel Koch, Transgaming Inc Status Complete. Version Last Modified Date: November 11, 2011 Author Revision: 24 Number OpenGL ES Extension #108 Dependencies OpenGL ES 1.0, OpenGL ES 2.0 or OpenGL 1.2 is required. OES_texture_npot, OES_texture_cube_map, OES_texture_3D, OES_depth_texture, OES_packed_depth_stencil, OES_compressed_paletted_texture, OES_texture_float, OES_texture_half_float EXT_texture_type_2_10_10_10_REV, EXT_texture_format_BGRA8888, EXT_texture3D, OES_texture_npot, APPLE_texture_2D_limited_npot, ARB_texture_cube_map, ARB_texture_cube_map_array, ARB_texture_rectangle, SGIS_generate_mipmap, EXT_direct_state_access, OES_EGL_image, WGL_ARB_render_texture, GLX_EXT_texture_from_pixmap, and core specifications that incorporate these extensions affect the definition of this extension. This extension is written against the OpenGL 3.2 Core Profile specification. Overview The texture image specification commands in OpenGL allow each level to be separately specified with different sizes, formats, types and so on, and only imposes consistency checks at draw time. This adds overhead for implementations. This extension provides a mechanism for specifying the entire structure of a texture in a single call, allowing certain consistency checks and memory allocations to be done up front. Once specified, the format and dimensions of the image array become immutable, to simplify completeness checks in the implementation. When using this extension, it is no longer possible to supply texture data using TexImage*. Instead, data can be uploaded using TexSubImage*, or produced by other means (such as render-to-texture, mipmap generation, or rendering to a sibling EGLImage). This extension has complicated interactions with other extensions. The goal of most of these interactions is to ensure that a texture is always mipmap complete (and cube complete for cubemap textures). IP Status No known IP claims New Procedures and Functions void TexStorage1DEXT(enum target, sizei levels, enum internalformat, sizei width); void TexStorage2DEXT(enum target, sizei levels, enum internalformat, sizei width, sizei height); void TexStorage3DEXT(enum target, sizei levels, enum internalformat, sizei width, sizei height, sizei depth); void TextureStorage1DEXT(uint texture, enum target, sizei levels, enum internalformat, sizei width); void TextureStorage2DEXT(uint texture, enum target, sizei levels, enum internalformat, sizei width, sizei height); void TextureStorage3DEXT(uint texture, enum target, sizei levels, enum internalformat, sizei width, sizei height, sizei depth); New Types None New Tokens Accepted by the <value> parameter of GetTexParameter{if}v: TEXTURE_IMMUTABLE_FORMAT_EXT 0x912F Accepted by the <internalformat> parameter of TexStorage* when implemented on OpenGL ES: ALPHA8_EXT 0x803C /* reuse tokens from EXT_texture */ LUMINANCE8_EXT 0x8040 LUMINANCE8_ALPHA8_EXT 0x8045 (if OES_texture_float is supported) RGBA32F_EXT 0x8814 /* reuse tokens from ARB_texture_float */ RGB32F_EXT 0x8815 ALPHA32F_EXT 0x8816 LUMINANCE32F_EXT 0x8818 LUMINANCE_ALPHA32F_EXT 0x8819 (if OES_texture_half_float is supported) RGBA16F_EXT 0x881A /* reuse tokens from ARB_texture_float */ RGB16F_EXT 0x881B ALPHA16F_EXT 0x881C LUMINANCE16F_EXT 0x881E LUMINANCE_ALPHA16F_EXT 0x881F (if EXT_texture_type_2_10_10_10_REV is supported) RGB10_A2_EXT 0x8059 /* reuse tokens from EXT_texture */ RGB10_EXT 0x8052 (if EXT_texture_format_BGRA8888 is supported) BGRA8_EXT 0x93A1 Additions to Chapter 2 of the OpenGL 3.2 Core Profile Specification (OpenGL Operation) None Additions to Chapter 3 of the OpenGL 3.2 Core Profile Specification (Rasterization) After section 3.8.1 (Texture Image Specification) add a new subsection called "Immutable-format texture images": "An alterative set of commands is provided for specifying the properties of all levels of a texture at once. Once a texture is specified with such a command, the format and dimensions of all levels becomes immutable, unless it is a proxy texture (since otherwise it would no longer be possible to use the proxy). The contents of the images and the parameters can still be modified. Such a texture is referred to as an "immutable-format" texture. The immutability status of a texture can be determined by calling GetTexParameter with <pname> TEXTURE_IMMUTABLE_FORMAT_EXT. Each of the commands below is described by pseudo-code which indicates the effect on the dimensions and format of the texture. For all of the commands, the following apply in addition to the pseudo-code: - If the default texture object is bound to <target>, an INVALID_OPERATION error is generated. - If executing the pseudo-code would lead to an error, the error is generated and the command will have no effect. - Any existing levels that are not replaced are reset to their initial state. - If <width>, <height>, <depth> or <levels> is less than 1, the error INVALID_VALUE is generated. - Since no pixel data are provided, the <format> and <type> values used in the pseudo-code are irrelevant; they can be considered to be any values that are legal to use with <internalformat>. - If the command is successful, TEXTURE_IMMUTABLE_FORMAT_EXT becomes TRUE. - If <internalformat> is a specific compressed texture format, then references to TexImage* should be replaced by CompressedTexImage*, with <format>, <type> and <data> replaced by any valid <imageSize> and <data>. If there is no <imageSize> for which this command would have been valid, an INVALID_OPERATION error is generated [fn: This condition is not required for OpenGL, but is necessary for OpenGL ES which does not support on-the-fly compression.] - If <internalformat> is one of the internal formats listed in table 3.11, an INVALID_ENUM error is generated. [fn: The corresponding table in OpenGL ES 2.0 is table 3.8.] The command void TexStorage1DEXT(enum target, sizei levels, enum internalformat, sizei width); specifies all the levels of a one-dimensional texture (or proxy) at the same time. It is described by the pseudo-code below: for (i = 0; i < levels; i++) { TexImage1D(target, i, internalformat, width, 0, format, type, NULL); width = max(1, floor(width / 2)); } If <target> is not TEXTURE_1D or PROXY_TEXTURE_1D then INVALID_ENUM is generated. If <levels> is greater than floor(log_2(width)) + 1 then INVALID_OPERATION is generated. The command void TexStorage2DEXT(enum target, sizei levels, enum internalformat, sizei width, sizei height); specifies all the levels of a two-dimensional, cube-map, one-dimension array or rectangle texture (or proxy) at the same time. The pseudo-code depends on the <target>: [PROXY_]TEXTURE_2D, [PROXY_]TEXTURE_RECTANGLE or PROXY_TEXTURE_CUBE_MAP: for (i = 0; i < levels; i++) { TexImage2D(target, i, internalformat, width, height, 0, format, type, NULL); width = max(1, floor(width / 2)); height = max(1, floor(height / 2)); } TEXTURE_CUBE_MAP: for (i = 0; i < levels; i++) { for face in (+X, -X, +Y, -Y, +Z, -Z) { TexImage2D(face, i, internalformat, width, height, 0, format, type, NULL); } width = max(1, floor(width / 2)); height = max(1, floor(height / 2)); } [PROXY_]TEXTURE_1D_ARRAY: for (i = 0; i < levels; i++) { TexImage2D(target, i, internalformat, width, height, 0, format, type, NULL); width = max(1, floor(width / 2)); } If <target> is not one of those listed above, the error INVALID_ENUM is generated. The error INVALID_OPERATION is generated if any of the following conditions hold: - <target> is [PROXY_]TEXTURE_1D_ARRAY and <levels> is greater than floor(log_2(width)) + 1 - <target> is not [PROXY_]TEXTURE_1D_ARRAY and <levels> is greater than floor(log_2(max(width, height))) + 1 The command void TexStorage3DEXT(enum target, sizei levels, enum internalformat, sizei width, sizei height, sizei depth); specifies all the levels of a three-dimensional, two-dimensional array texture, or cube-map array texture (or proxy). The pseudo-code depends on <target>: [PROXY_]TEXTURE_3D: for (i = 0; i < levels; i++) { TexImage3D(target, i, internalformat, width, height, depth, 0, format, type, NULL); width = max(1, floor(width / 2)); height = max(1, floor(height / 2)); depth = max(1, floor(depth / 2)); } [PROXY_]TEXTURE_2D_ARRAY, [PROXY_]TEXTURE_CUBE_MAP_ARRAY_ARB: for (i = 0; i < levels; i++) { TexImage3D(target, i, internalformat, width, height, depth, 0, format, type, NULL); width = max(1, floor(width / 2)); height = max(1, floor(height / 2)); } If <target> is not one of those listed above, the error INVALID_ENUM is generated. The error INVALID_OPERATION is generated if any of the following conditions hold: - <target> is [PROXY_]TEXTURE_3D and <levels> is greater than floor(log_2(max(width, height, depth))) + 1 - <target> is [PROXY_]TEXTURE_2D_ARRAY or [PROXY_]TEXTURE_CUBE_MAP_ARRAY_EXT and <levels> is greater than floor(log_2(max(width, height))) + 1 After a successful call to any TexStorage* command with a non-proxy target, the value of TEXTURE_IMMUTABLE_FORMAT_EXT for this texture object is set to TRUE, and no further changes to the dimensions or format of the texture object may be made. Other commands may only alter the texel values and texture parameters. Using any of the following commands with the same texture will result in the error INVALID_OPERATION being generated, even if it does not affect the dimensions or format: - TexImage* - CompressedTexImage* - CopyTexImage* - TexStorage* The TextureStorage* commands operate identically to the corresponding command where "Texture" is substituted for "Tex" except, rather than updating the current bound texture for the texture unit indicated by the current active texture state and the target parameter, these "Texture" commands update the texture object named by the initial texture parameter. The error INVALID_VALUE is generated if <texture> is zero. " In section 3.8.6 (Texture Parameters), after the sentence "In the remainder of section 3.8, denote by lod_min, lod_max, level_base, and level_max the values of the texture parameters TEXTURE_MIN_LOD, TEXTURE_MAX_LOD, TEXTURE_BASE_LEVEL, and TEXTURE_MAX_LEVEL respectively." add "However, if TEXTURE_IMMUTABLE_FORMAT_EXT is TRUE, then level_base is clamped to the range [0, <levels> - 1] and level_max is then clamped to the range [level_base, <levels> - 1], where <levels> is the parameter passed the call to TexStorage* for the texture object. In section 3.8.9 (Rendering feedback loops) replace all references to TEXTURE_BASE_LEVEL by level_base. In section 3.8.9 (Mipmapping), replace the paragraph starting "Each array in a mipmap is defined..." by "Each array in a mipmap is defined using TexImage3D, TexImage2D, CopyTexImage2D, TexImage1D, CopyTexImage1D, or by functions that are defined in terms of these functions. Level-of-detail numbers proceed from level_base for the original texel array through the maximum level p, with each unit increase indicating an array of half the dimensions of the previous one (rounded down to the next integer if fractional) as already described. For immutable-format textures, p is one less than the <levels> parameter passed to TexStorage*; otherwise p = floor(log_2(maxsize)) + level_base. All arrays from level_base through q = min(p, level_max) must be defined, as discussed in section 3.8.12." In section 3.8.12 (Texture Completeness), modify the last sentence to avoid refering to level_base and level_max: "An implementation may allow a texture image array of level 1 or greater to be created only if a mipmap complete set of image arrays consistent with the requested array can be supported where the values of TEXTURE_BASE_LEVEL and TEXTURE_MAX_LEVEL are 0 and 1000 respectively." Modify section 3.8.13 (Texture State and Proxy State) to add the new state: "Each set consists of ..., and a boolean flag indicating whether the format and dimensions of the texture are immutable." Add "The initial value of TEXTURE_IMMUTABLE_FORMAT_EXT is FALSE." Additions to Chapter 4 of the OpenGL 3.2 Core Profile Specification (Per-Fragment Operations and the Frame Buffer) None Additions to Chapter 5 of the OpenGL 3.2 Compatibility Profile Specification (Special Functions) In section 5.4.1 (Commands Not Usable in Display Lists), add TexStorage* to the list of commands that cannot be used. Additions to Chapter 6 of the OpenGL 3.2 Core Profile Specification (State and State Requests) Replace the following statement in 6.1.3 (Enumerated Queries): "<value> must be one of the symbolic values in table 3.10." with "<value> must be TEXTURE_IMMUTABLE_FORMAT_EXT or one of the symbolic values in table 3.22." Additions to the AGL/EGL/GLX/WGL Specifications None Additions to OES_compressed_ETC1_RGB8_texture Add the following to the additions to Chapter 3: "Since ETC1 images are easily edited along 4x4 texel boundaries, the limitations on CompressedTexSubImage2D are relaxed. CompressedTexSubImage2D will result in an INVALID_OPERATION error only if one of the following conditions occurs: * <width> is not a multiple of four, and <width> plus <xoffset> is not equal to the texture width; * <height> is not a multiple of four, and <height> plus <yoffset> is not equal to the texture height; or * <xoffset> or <yoffset> is not a multiple of four. Remove CompressedTexSubImage2D from this error: "INVALID_OPERATION is generated by CompressedTexSubImage2D, TexSubImage2D, or CopyTexSubImage2D if the texture image <level> bound to <target> has internal format ETC1_RGB8_OES." Add the following error: "INVALID_OPERATION is generated by CompressedTexSubImage2D if the region to be modified is not aligned to block boundaries (refer to the extension text for details)." Additions to AMD_compressed_ATC_texture and AMD_compressed_3DC_texture: Apply the same changes as for OES_compressed_ETC1_RGB8_texture above, substituting the appropriate internal format tokens from these extensions. Dependencies on EXT_direct_state_access If EXT_direct_state_access is not present, references to TextureStorage* should be ignored. Dependencies on OpenGL ES On OpenGL ES without extensions introducing TEXTURE_MAX_LEVEL, mipmapped textures specified with TexStorage are required to have a full set of mipmaps. If TEXTURE_MAX_LEVEL is not supported, this extension is modified as follows: - Where an upper bound is placed on <levels> in this extension (i.e. the maximum number of mipmap levels for a texture of the given target and dimensions), an INVALID_OPERATION error is generated if <levels> is neither 1 nor this upper bound. - q (the effective maximum number of levels) is redefined to clamp to the number of levels present in immutable-format textures. OpenGL ES does not accept sized internal formats (e.g., RGBA8) and instead derives an internal format from the <format> and <type> parameters of TexImage2D. Since TexStorage* does not specify texel data, the API doesn't include <format> and <type> parameters. On an OpenGL ES implementation, the values in the <internalformat> column in the tables below are accepted as <internalformat> parameters, and base internal formats are not accepted. The TexImage* calls in the TexStorage* pseudocode are modified so that the <internalformat>, <format> and <type> parameters are taken from the <format>, <format> and <type> columns (respectively) in the tables below, according to the <internalformat> specified in the TexStorage* command. <internalformat> <format> <type> ---------------- -------- ------ RGB565 RGB UNSIGNED_SHORT_5_6_5 RGBA4 RGBA UNSIGNED_SHORT_4_4_4_4 RGB5_A1 RGBA UNSIGNED_SHORT_5_5_5_1 RGB8_OES RGB UNSIGNED_BYTE RGBA8_OES RGBA UNSIGNED_BYTE LUMINANCE8_ALPHA8_EXT LUMINANCE_ALPHA UNSIGNED_BYTE LUMINANCE8_EXT LUMINANCE UNSIGNED_BYTE ALPHA8_EXT ALPHA UNSIGNED_BYTE If OES_depth_texture is supported: <internalformat> <format> <type> ---------------- -------- ------ DEPTH_COMPONENT16_OES DEPTH_COMPONENT UNSIGNED_SHORT DEPTH_COMPONENT32_OES DEPTH_COMPONENT UNSIGNED_INT If OES_packed_depth_stencil is supported: <internalformat> <format> <type> ---------------- -------- ------ DEPTH24_STENCIL8_OES DEPTH_STENCIL_OES UNSIGNED_INT If OES_texture_float is supported: <internalformat> <format> <type> ---------------- -------- ------ RGBA32F_EXT RGBA FLOAT RGB32F_EXT RGB FLOAT LUMINANCE_ALPHA32F_EXT LUMINANCE_ALPHA FLOAT LUMINANCE32F_EXT LUMINANCE FLOAT ALPHA32F_EXT ALPHA FLOAT If OES_texture_half_float is supported: <internalformat> <format> <type> ---------------- -------- ------ RGBA16F_EXT RGBA HALF_FLOAT_OES RGB16F_EXT RGB HALF_FLOAT_OES LUMINANCE_ALPHA16F_EXT LUMINANCE_ALPHA HALF_FLOAT_OES LUMINANCE16F_EXT LUMINANCE HALF_FLOAT_OES ALPHA16F_EXT ALPHA HALF_FLOAT_OES If EXT_texture_type_2_10_10_10_REV is supported: <internalformat> <format> <type> ---------------- -------- ------ RGB10_A2_EXT RGBA UNSIGNED_INT_2_10_10_10_REV_EXT RGB10_EXT RGB UNSIGNED_INT_2_10_10_10_REV_EXT If EXT_texture_format_BGRA8888 is supported: <internalformat> <format> <type> ---------------- -------- ------ BGRA8_EXT BGRA_EXT UNSIGNED_BYTE Dependencies on texture targets If a particular texture target is not supported by the implementation, passing it as a <target> to TexStorage* will generate an INVALID_ENUM error. If as a result, any of the commands defined in this extension would no longer have any valid <target>, all references to the command should be ignored. In particular, note that OpenGL ES 1.x/2.0 do not have proxy textures, 1D textures, or 3D textures, and thus only the TexStorage2DEXT entry point is required. If OES_texture_3D is supported, the TexStorage3DEXT entry point is also required. Dependencies on OES_texture_npot If OpenGL ES 2.0 or APPLE_texture_2D_limited_npot is present but OES_texture_npot is not present, then INVALID_OPERATION is generated by TexStorage* and TexStorage3DEXT if <levels> is not one and <width>, <height> or <depth> is not a power of two. Dependencies on WGL_ARB_render_texture, GLX_EXT_texture_from_pixmap, EGL 1.4 and GL_OES_EGL_image The commands eglBindTexImage, wglBindTexImageARB, glXBindTexImageEXT or EGLImageTargetTexture2DOES are not permitted on an immutable-format texture. They will generate the following errors: - EGLImageTargetTexture2DOES: INVALID_OPERATION - eglBindTexImage: EGL_BAD_MATCH - wglBindTexImage: ERROR_INVALID_OPERATION - glXBindTexImageEXT: BadMatch Dependencies on OES_compressed_paletted_texture The compressed texture formats exposed by OES_compressed_paletted_texture are not supported by TexStorage*. Passing one of these tokens to TexStorage* will generate an INVALID_ENUM error. Errors Note that dependencies above modify the errors. If TexStorage* is called with a <width>, <height>, <depth> or <levels> parameter that is less than one, then the error INVALID_VALUE is generated. If the <target> parameter to TexStorage1DEXT is not [PROXY_]TEXTURE_1D, then the error INVALID_ENUM is generated. If the <target> parameter to TexStorage2DEXT is not [PROXY_]TEXTURE_2D, [PROXY_]TEXTURE_CUBE_MAP, [PROXY_]TEXTURE_RECTANGLE or [PROXY_]TEXTURE_1D_ARRAY, then the error INVALID_ENUM is generated. If the <target> parameter to TexStorage3DEXT is not [PROXY_]TEXTURE_3D, [PROXY_]TEXTURE_2D_ARRAY or [PROXY_]TEXTURE_CUBE_MAP_ARRAY then the error INVALID_ENUM is generated. If the <levels> parameter to TexStorage* is greater than the <target>-specific value listed below then the error INVALID_OPERATION is generated: [PROXY_]TEXTURE_{1D,1D_ARRAY}: floor(log_2(width)) + 1 [PROXY_]TEXTURE_{2D,2D_ARRAY,CUBE_MAP,CUBE_MAP_ARRAY}: floor(log_2(max(width, height))) + 1 [PROXY_]TEXTURE_3D: floor(log_2(max(width, height, depth))) + 1 [PROXY_]TEXTURE_RECTANGLE: 1 If the default texture object is bound to the <target> passed to TexStorage*, then the error INVALID_OPERATION is generated. If the <target> parameter to TextureStorage* does not match the dimensionality of <texture>, then the error INVALID_OPERATION is generated. If the <texture> parameter to TextureStorage* is zero, then the INVALID_VALUE is generated. If any pseudo-code listed in this extension would generate an error, then that error is generated. Calling any of the following functions on a texture for which TEXTURE_IMMUTABLE_FORMAT_EXT is TRUE will generate an INVALID_OPERATION error: - TexImage* - CompressedTexImage* - CopyTexImage* New State Additions to Table 6.8 Textures (state per texture object) Initial Get Value Type Get Command Value Description Sec. --------- ---- ----------- ------- ----------- ---- TEXTURE_IMMUTABLE_FORMAT_EXT B GetTexParameter FALSE Size and format immutable 2.6 New Implementation Dependent State None Issues 1. What should this extension be called? RESOLVED: EXT_texture_storage is chosen for consistency with the glRenderbufferStorage entry point. 2. Should TexStorage* accept a border parameter? RESOLVED: no. DISCUSSION: Currently it does not, since borders are a deprecated feature which is not supported by all hardware. Users of the compatibility profile can continue to use the existing texture specification functions, but there is an argument that users of compatibility profile may also want to use this extension. 3. What is the correct error when <levels> specifies a partial mipmap pyramid for OpenGL ES? RESOLVED: INVALID_OPERATION, since it is an interaction between parameters rather than a single value being invalid. It also makes sense to relax this condition for desktop GL where it makes sense to use a truncated pyramid with TEXTURE_MAX_LEVEL. 4. Should use of these entry-points make the metadata (format and dimensions) immutable? RESOLVED: Yes. DISCUSSION: The benefits of knowing metadata can't change will probably outweigh the extra cost of checking the TEXTURE_IMMUTABLE_FORMAT_EXT flag on each texture specification call. 5. Should it be legal to completely replace the texture using a new call to TexStorage*? RESOLVED. It will not be allowed. DISCUSSION: This is useful to invalidate all levels of a texture. Allowing the metadata to be changed here seems easier than trying to define a portable definition of what it means to change the metadata (e.g. what if you used an unsized internal format the first time and the corresponding sized internal format the second time, or vice versa)? However, while this is largely similar to deleting the old texture object and replacing it with a new one, it does lose some of the advantages of immutability. Specifically, because doing so does not reset bindings, it doesn't allow a migration path to an API that validates the texture format at bind time. 6. Should it be legal to use TexImage* after TexStorage* if it doesn't affect the metadata? RESOLVED: No. DISCUSSION: A potential use case is to allow a single level of a texture to be invalidated using a NULL pointer. However, as noted above it is non-trivial to determine what constitutes a change. 7. How does this extension interact with APPLE_texture_2D_limited_npot? RESOLVED. APPLE_texture_2D_limited_npot is equivalent to the NPOT support in OpenGL ES 2.0. 8. Should this extension be written to work with desktop OpenGL? RESOLVED: Yes. DISCUSSION: There has been been interest and it will future-proof it against further additions to OpenGL ES. 9. Which texture targets should be supported? RESOLVED. All targets except multisample and buffer textures are supported. Initially all targets except TEXTURE_BUFFER were supported. It was noted that the entrypoints for multisample targets added no useful functionality, since multisample textures have no completeness checks beyond being non-empty. Rectangle textures have completeness checks to prevent filtering of integer textures. However, since we decided to only force mipmap completeness, this becomes less useful. 10. Should this extension support proxy textures? RESOLVED: Yes. DISCUSSION: It should be orthogonal. 11. Are the <format> and <type> parameters necessary? RESOLVED. No, they will be removed. DISCUSSION: For OpenGL ES the type parameter was necessary to determine the precision of the texture, but this can be solved by having these functions accept sized internal formats (which are already accepted by renderbuffers). 12. Should it be legal to make the default texture (id 0) immutable-format? RESOLVED: No. DISCUSSION: This would make it impossible to restore the context to it's default state, which is deemed undesirable. There is no good reason not to use named texture objects. 13. Should we try to guarantee that textures made through this path will always be complete? RESOLVED: It should be guaranteed that the texture will be mipmap complete. DISCUSSION: Future separation between images and samplers will still allow users to create combinations that are invalid, but constraining the simple cases will make these APIs easier to use for beginners. 14. Should these functions use a EXT_direct_state_access approach to specifying the texture objects? UNRESOLVED. DISCUSSION: as a standalone extension, no DSA-like functions will be added. However, interactions with EXT_direct_state_access and ARB_direct_state_access need to be resolved. 15. Should these functions accept generic compressed formats? RESOLVED: Yes. Note that the spec language will need to be modified to allow this for ES, since the pseudocode is written in terms of TexImage2D, which does not allow compressed texture formats in ES. See also issues 23 and 27. 16. How should completeness be forced when TEXTURE_MAX_LEVEL is not present? RESOLVED. The maximum level q will be redefined to clamp to the highest level available. DISCUSSION: A single-level texture can be made complete either by making it mipmap complete (by setting TEXTURE_MAX_LEVEL to 0) or by turning off mipmapping (by choose an appropriate minification filter). Some options: A: Specify that TexStorage* changes the default minification filter for OpenGL ES. This makes it awkward to add TEXTURE_MAX_LEVEL support to OpenGL ES later, since switching to match GL would break compatibility. The two mechanisms also do not give identical results, since the magnification threshold depends on the minification filter. B: Specify that the texture behaves as though TEXTURE_MAX_LEVEL were zero. To specify this properly probably requires fairly intrusive changes to the OpenGL ES full specification to add back all the language relating to the max level. It also does not solve the similar problem of what to do with NPOT textures; and it may have hardware impacts due to the change in the min/mag crossover. C: Specify that TexStorage* changes the default minification filter for all implementations when a single-level texture is specified. This may be slightly counter-intuitive to desktop GL users, but will give consistent behaviour across variants of GL and avoids changing the functional behaviour of this extension based on the presence or absence of some other feature. Currently B is specified. This has potential hardware implications for OpenGL ES because of the effect of the minification filter on the min/mag crossover. However, C has potential hardware implications for OpenGL due to the separation of texture and sampler state. 17. How should completeness be forced when only ES2-style NPOT is available? RESOLVED. It is not worth trying to do this, in light of issue 13. Previous revisions of this extension overrode the minification filter and wrap modes, but that is no longer the case. Since OES_texture_npot removes the caveats on NPOT textures anyway, it might not be worth trying to "fix" this. 18. For OpenGL ES, how do the new sized internal formats interact with OES_required_internal_format? RESOLVED. If OES_required_internal_format is not present, then the <internalformat> parameter is intended merely to indicate what the corresponding <format> and <type> would have been, had TexImage* been used instead. If OES_required_internal_format is present, then it is intended that the <internalformat> will be interpreted as if it had been passed directly to TexImage*. 19. Should there be some hinting mechanism to indicate whether data is coming immediately or later? RESOLVED. No parameter is needed. An extension can be added to provide a TexParameter value which is latched at TexStorage time. DISCUSSION: Some members felt that this would be useful so that they could defer allocation when suitable, particularly if higher- resolution images will be streamed in later; or to choose a memory type or layout appropriate to the usage. However, implementation experience with BufferData is that developers frequently provide wrong values and implementations have to guess anyway. One option suggested was the <usage> parameter currently passed to BufferData. Another option was to set it with TexParameter. 20. How should this extension interact with EGLImageTargetTexture2DOES, eglBindTexImage, glXBindTexImage and wglBindTexImage? RESOLVED. These functions will not be permitted after glTexStorage*. Several options are possible: A) Disallow these functions. B) Allow them, but have them reset the TEXTURE_IMMUTABLE_FORMAT_EXT flag. C) Allow them unconditionally. C would violate the design principle that the dimensions and format of the mipmap array are immutable. B does not so much modify the dimension and formats as replace them with an entirely different set. 21. Should there be a single function for specifying 1D, 2D and 3D targets? RESOLVED. No, we will stick with existing precedent. 22. Is it possible to use GenerateMipmap with an incomplete mipmap pyramid? RESOLVED. Yes, because the effective max level is limited to the levels that were specified, and so GenerateMipmap does not generate any new levels. However, to make automatic mipmap generation work, it is necessary to redefine p rather than q, since automatic mipmap generation ignores the max level. 23. How should this extension interact with OES_compressed_paletted_texture? RESOLVED. Paletted textures will not be permitted, and will generate INVALID_ENUM. DISCUSSION: OES_compressed_paletted_texture supplies all the mipmaps in a single function call, with the palette specified once. That's incompatible with the upload model in this extension. 24. How can ETC1 textures be used with this extension? RESOLVED. Add language in this extension to allow subregion uploads for ETC1. DISCUSSION: GL_OES_compressed_ETC1_RGB8_texture doesn't allow CompressedTexSubImage*, so it would be impossible to use this extension with ETC1. This is seen as an oversight in the ETC1 extension. While it cannot be fixed in that extension (since it is already shipping), this extension can add that capability. 25. Should any other compressed formats be similarly modified? RESOLVED. Yes, AMD_compressed_ATC_texture and AMD_compressed_3DC_texture can be modified similarly to ETC1 (Maurice Ribble indicated that both formats use 4x4 blocks). Desktop OpenGL requires that whole-image replacement is supported for any compressed texture format, and the OpenGL ES extensions EXT_texture_compression_dxt1 and IMG_texture_compression_pvrtc already allow whole-image replacement, so it is not necessary to modify them to be used with this extension. 26. Should these commands be permitted in display lists? RESOLVED. No. DISCUSSION: Display lists are most useful for repeating commands, and TexStorage* commands cannot be repeated because the first call makes the format immutable. 27. Should these commands accept unsized internal formats? RESOLVED: No, for both OpenGL and OpenGL ES. DISCUSSION: normally the <type> parameter to TexImage* can serve as a hint to select a sized format (and in OpenGL ES, this is the only mechanism available); since TexStorage* does not have a <type> parameter, the implementation has no information on which to base a decision. Revision History Revision 24, 2011/11/11 (dgkoch) - Mark complete. Clarify ES clarifications. Revision 23, 2011/11/10 (dgkoch) - Add GLES clarifcations and interactions with more GLES extensions Revision 22, 2011/11/10 (bmerry) - Update my contact details Revision 21, 2011/07/25 (bmerry) - Remove dangling references to MultiTexStorage in Errors section Revision 20, 2011/07/21 (bmerry) - Remove dangling reference to <samples> in Errors section Revision 19, 2011/05/02 (Jon Leech) - Assign enum value Revision 18, 2011/01/24 (bmerry) - Disallow unsized internal formats (oversight in revision 17). Revision 17, 2011/01/24 (bmerry) - Added and resolved issue 26. - Split issue 27 out from issue 15. - Disallow TexStorage* in display lists. - Use the term "immutable-format" consistently (bug 7281). Revision 16, 2010/11/23 (bmerry) - Disallowed TexStorage on an immutable-format texture (resolves issue 5). - Deleted MultiTexStorage* commands (other DSA functions still unresolved). - Some minor wording changes suggested by Pat Brown (bug 7002). Revision 15, 2010/11/09 (bmerry) - Reopened issue 5. - Reopened issue 14, pending stabilisation of ARB_direct_state_access. - Marked issue 9 resolved, pending any objections. - Fix references to no object being bound (was meant to refer to the default object). - Adding missing pseudocode for TEXTURE_1D_ARRAY. - Corrected TEXTURE_2D_ARRAY -> TEXTURE_1D_ARRAY in error checks. - Changed "levels... are removed" to "levels... are reset to their init state", since desktop GL has per-level state apart from the texels. - Miscellaneous wording fixes. Revision 14, 2010/09/25 (bmerry) - Add issues 24-25 and alterations to OES_compressed_ETC1_RGB8_texture, AMD_compressed_ATC_texture and AMD_compressed_3DC_texture. Revision 13, 2010/09/19 (bmerry) - Two typo fixes from Daniel Koch Revision 12, 2010/09/18 (bmerry) - Changed resolution to issue 20 - Added and resolved issue 23 - Added explanation of how to upload data (in overview) - Added spec language to implement resolution to issue 15 Revision 11, 2010/07/21 (bmerry) - Resolved issue 16 - Reopen issue 20 - Fix some typos Revision 10, 2010/07/15 (bmerry) - Update some issues to match core text - Resolved issue 17 Revision 9, 2010/05/24 (bmerry) - Marked issue 2 as resolved - Resolved issue 19 (as no change) - Resolved issue 20 - Add issues 21-22 - Add in spec language to forbid use on default textures - Redefine level_base, level_max to be clamped forms of TEXTURE_BASE_LEVEL/TEXTURE_MAX_LEVEL when using immutable textures - Redefine p to also be clamped to the provided levels for immutable textures, to support automatic mipmap generation - Removed multisample functions - Removed language stating that texture parameters were reset to defaults Revision 8, 2010/05/18 (bmerry) - Added issue about EGLimage - Marked issue 14 as resolved Revision 7, 2010/05/04 (bmerry) - Removed some lingering <format>, <type> parameters to the new functions that should have been removed in revision 4 - Trivial typo fixes Revision 6, 2010/02/18 (bmerry) - Resolved issues 5, 6 and 18 - Added MultiTexStorage* functions for DSA interaction - Added error for texture-target mismatch in DSA - Allowed TexStorage* to be called again Revision 5, 2010/01/25 (bmerry) - Added to contributors list - Require OpenGL 1.2, to simplify interactions with TEXTURE_BASE_LEVEL/TEXTURE_MAX_LEVEL and CLAMP_TO_EDGE - Change default wrap modes to always be CLAMP_TO_EDGE - Change default filters to always be NEAREST - Moved language about generating new levels into an interaction, since it can only happen on OpenGL ES - Added interaction with EXT_direct_state_access - Added extra <internalformats> for GL ES when OES_depth_texture, OES_packed_depth_stencil and EXT_texture_type_2_10_10_10_REV are present. - Minor non-functional wording fixes and typos - Resolved issue 16 - Added issues 17-19 Revision 4, 2010/01/13 (bmerry) - Changed suffix from ARM to EXT - Added list of contributors - Added language to force the texture to always be complete - Removed <format> and <type> arguments - Added issues 14-16 - Reopened issue 2 - Reformatted issues to separate resolution and discussion - Resolved issues 1, 9 and 11-13 - Fixed the max number of levels in a cube map array Revision 3, 2009/12/17 (bmerry) - Added missing vendor suffix to TEXTURE_IMMUTABLE_FORMAT_ARM - Rewritten to against desktop OpenGL - Added prototypes for 1D and multisample storage functions - Added issues 8-13 Revision 2, 2009/08/20 (bmerry) - Resolved issue 2 (no border parameter) - Resolved issue 4 (metadata becomes immutable) - Added interaction with OES_texture_cube_map - Added error if width != height in a cube map - Added issues 5-7 Revision 1, 2009/05/06 (bmerry) - First draft