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kc3-lang/angle/extensions/ANGLE_depth_texture.txt
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shannon.woods@transgaming.com
Date : 2013-02-28 23:20:20
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Message : Updates ANGLE_depth_texture to reflect proposed changes in requirements for g and b channels. git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1967 736b8ea6-26fd-11df-bfd4-992fa37f6226
- extensions/ANGLE_depth_texture.txt
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Name ANGLE_depth_texture Name Strings GL_ANGLE_depth_texture Contributors Nicolas Capens, TransGaming Daniel Koch, TransGaming Shannon Woods, TransGaming Kenneth Russell, Google Vangelis Kokkevis, Google Gregg Tavares, Google Contributors to OES_depth_texture Contributors to OES_packed_depth_stencil Contact Shannon Woods, TransGaming (shannon 'dot' woods 'at' transgaming.com) Status Implemented in ANGLE. Version Last Modified Date: February 25, 2013 Revision: #4 Number TBD Dependencies OpenGL ES 2.0 is required. This extension is written against the OpenGL ES 2.0.25 specification OES_packed_depth_stencil affects the definition of this extension. EXT_texture_storage affects the definition of this extension. Overview This extension defines support for 2D depth and depth-stencil textures in an OpenGL ES implementation. This extension incorporates the depth texturing functionality of OES_depth_texture and OES_packed_depth_stencil, but does not provide the ability to load existing data via TexImage2D or TexSubImage2D. This extension also allows implementation variability in which components from a sampled depth texture contain the depth data. Depth textures created with this extension only support 1 level. New Procedures and Functions None New Tokens Accepted by the <format> parameter of TexImage2D and TexSubImage2D and <internalformat> parameter of TexImage2D: DEPTH_COMPONENT 0x1902 DEPTH_STENCIL_OES 0x84F9 Accepted by the <type> parameter of TexImage2D, TexSubImage2D: UNSIGNED_SHORT 0x1403 UNSIGNED_INT 0x1405 UNSIGNED_INT_24_8_OES 0x84FA Accepted by the <internalformat> parameter of TexStorage2DEXT: DEPTH_COMPONENT16 0x81A5 DEPTH_COMPONENT32_OES 0x81A7 DEPTH24_STENCIL8_OES 0x88F0 Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL Operation) Update Section 2.10.5 "Shader Execution" in the subsection titled "Texture Access" add a new paragraph before the last paragraph add this line: "The stencil index texture internal component is ignored if the base internal format is DEPTH_STENCIL_OES. If a vertex shader uses..." Additions to Chapter 3 of the OpenGL ES 2.0 specification (Rasterization) Add the following rows to Table 3.2 (page 62): type Parameter GL Data Type Special ------------------------------------------------ ... ... ... UNSIGNED_SHORT ushort No UNSIGNED_INT uint No UNSIGNED_INT_24_8_OES uint Yes Add the following rows to Table 3.3 (page 62): Format Name Element Meaning and Order Target Buffer ------------------------------------------------------------------ ... ... ... DEPTH_COMPONENT Depth Depth DEPTH_STENCIL_OES Depth and Stencil Index Depth and Stencil ... ... ... Add a row to Table 3.5 "Packed pixel formats" (page 64): type Parameter GL Type Components Pixel Formats ------------------------------------------------------------------ ... ... ... ... UNSIGNED_INT_24_8_OES uint 2 DEPTH_STENCIL_OES Add a new table after Table 3.6 (page 64): UNSIGNED_INT_24_8_OES 31 30 29 28 27 26 ... 12 11 10 9 8 7 6 5 4 3 2 1 0 +----------------------------------+---------------+ | 1st Component | 2nd Component | +----------------------------------+---------------+ Table 3.6.B: UNSIGNED_INT formats Add a row to Table 3.7 "Packed pixel field assignments" (page 65): Format | 1st 2nd 3rd 4th ------------------+------------------------------- ... | ... ... ... ... DEPTH_STENCIL_OES | depth stencil N/A N/A Add the following paragraph to the end of the section "Conversion to floating-point" (page 65): "For groups of components that contain both standard components and index elements, such as DEPTH_STENCIL_OES, the index elements are not converted." In section 3.7.1 "Texture Image Specification", update page 67 to say: "The selected groups are processed as described in section 3.6.2, stopping just before final conversion. Each R, G, B, A, or depth value so generated is clamped to [0, 1], while the stencil index values are masked by 2^n-1, where n is the number of stencil bits in the internal format resolution (see below). Components are then selected from the resulting R, G, B, A, depth, or stencil index values to obtain a texture with the base internal format specified by <internalformat>. Table 3.8 summarizes the mapping of R, G, B, A, depth, or stencil values to texture components, as a function of the base internal format of the texture image. <internalformat> may be specified as one of the internal format symbolic constants listed in table 3.8. Specifying a value for <internalformat> that is not one of the above values generates the error INVALID_VALUE. If <internalformat> does not match <format>, the error INVALID_OPERATION is generated. Textures with a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES are supported by texture image specification commands only if <target> is TEXTURE_2D. Using these formats in conjunction with any other <target> will result in an INVALID_OPERATION error. Textures with a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES only support one level of image data. Specifying a non-zero value for <level> will result in an INVALID_OPERATION error. Textures with a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES require either depth component data or depth/stencil component data. Textures with other base internal formats require RGBA component data. The error INVALID_OPERATION is generated if the base internal format is DEPTH_COMPONENT or DEPTH_STENCIL_OES and <format> is not DEPTH_COMPONENT or DEPTH_STENCIL_OES, or if the base internal format is not DEPTH_COMPONENT or DEPTH_STENCIL_OES and <format> is DEPTH_COMPONENT or DEPTH_STENCIL_OES. Textures with a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES do not support loading image data via the TexImage commands. They can only have their contents specified by rendering to them. The INVALID_OPERATION error is generated by the TexImage2D command if <data> is not NULL for such textures." Add a row to table 3.8 (page 68), and update the title of the second column: Base Internal Format RGBA, Depth and Stencil Values Internal Components ------------------------------------------------------------------------- ... ... ... DEPTH_COMPONENT Depth D DEPTH_STENCIL_OES Depth,Stencil D,S ... ... ... Update the caption for table 3.8 (page 68) "Table 3.8: Conversion from RGBA, depth, and stencil pixel components to internal texture components. Texture components R, G, B, A, and L are converted back to RGBA colors during filtering as shown in table 3.12. Texture components D are converted to RGBA colors as described in section 3.7.8-1/2." Add the following to section 3.7.2 "Alternate Texture Image Specification Commands": "CopyTexImage2D and CopyTexSubImage2D generate the INVALID_OPERATION error if the base internal format of the destination texture is DEPTH_COMPONENT or DEPTH_STENCIL_OES. TexSubImage2D generates the INVALID_OPERATION error if the base internal format of the texture is DEPTH_COMPONENT or DEPTH_STENCIL_OES." Add a new section between sections 3.7.8 and 3.7.9: "3.7.8-1/2 Depth/Stencil Textures If the currently bound texture's base internal format is DEPTH_COMPONENT or DEPTH_STENCIL_OES, then the output of the texture unit is as described below. Otherwise, the texture unit operates in the normal manner. Let <D_t> be the depth texture value, provided by the shader's texture lookup function. Then the effective texture value is computed as follows: <Tau> = <D_t> If the texture image has a base internal format of DEPTH_STENCIL_OES, then the stencil index texture component is ignored. The texture value <Tau> does not include a stencil index component, but includes only the depth component. The resulting <Tau> is assigned to <R_t>. In some implementations, <Tau> is also assigned to <G_t>, <B_t>, or <A_t>. Thus in table 3.12, textures with depth component data behave as if their base internal format is RGBA, with values in <G_t>, <B_t>, and <A_t> being implementation dependent." Add the following to section 3.7.11 "Mipmap Generation": "If the level zero array contains depth or depth-stencil data, the error INVALID_OPERATION is generated." Insert a new paragraph after the first paragraph of the "Texture Access" subsection of section 3.8.2 on page 87, which says: "Texture lookups involving textures with depth component data generate a texture source color by using depth data directly, as described in section 3.7.8-1/2. The stencil texture internal component is ignored if the base internal format is DEPTH_STENCIL_OES." Additions to Chapter 4 of the OpenGL ES 2.0 specification (Per-Fragment Operations and the Framebuffer) In section 4.4.5 "Framebuffer Completeness", replace the the 3rd paragraph with the following text: "* An internal format is color-renderable if it is one of the formats from table 4.5 noted as color-renderable or if it is unsized format RGBA or RGB. No other formats, including compressed internal formats, are color-renderable. * An internal format is depth-renderable if it is one of the sized internal formats from table 4.5 noted as depth-renderable, if it is the unsized format DEPTH_COMPONENT or if it is the internal format value of DEPTH24_STENCIL8_OES. No other formats are depth-renderable. * An internal format is stencil-renderable if it is one of the sized internal formats from table 4.5 noted as stencil-renderable or if it is DEPTH24_STENCIL8_OES. No other formats are stencil-renderable." Additions to Chapter 5 of the OpenGL ES 2.0 Specification (Special Functions) None. Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State Requests) None. Interactions with OES_packed_depth_stencil If OES_packed_depth_stencil is not supported, mentions of DEPTH_STENCIL_OES and UNSIGNED_INT_24_8_OES as a format/type combinations for TexImage2D and TexSubImage2D are omitted. Mentions of the internal format DEPTH24_STENCIL8_OES are also omitted. Interactions with EXT_texture_storage If EXT_texture_storage is supported the following internalformat to format/type mappings are used: <internalformat> <format> <type> ---------------- -------- ------ DEPTH_COMPONENT16 DEPTH_COMPONENT UNSIGNED_SHORT DEPTH_COMPONENT32_OES DEPTH_COMPONENT UNSIGNED_INT DEPTH24_STENCIL8_OES DEPTH_STENCIL_OES UNSIGNED_INT Textures with the above <internalformats> only support one level of image data. Specifying a value other than one for the <levels> parameter to TexStorage2DEXT will result in an INVALID_OPERATION error. If EXT_texture_storage is not supported, ignore any references to TexStorage2DEXT. Errors The error INVALID_OPERATION is generated by TexImage2D if <format> and <internalformat> are DEPTH_COMPONENT and <type> is not UNSIGNED_SHORT, or UNSIGNED_INT. The error INVALID_OPERATION is generated by TexSubImage2D if <format> is DEPTH_COMPONENT and <type> is not UNSIGNED_SHORT, or UNSIGNED_INT. The error INVALID_OPERATION is generated by TexImage2D if <format> and <internalformat> are not DEPTH_COMPONENT and <type> is UNSIGNED_SHORT, or UNSIGNED_INT. The error INVALID_OPERATION is generated by TexSubImage2D if <format> is not DEPTH_COMPONENT and <type> is UNSIGNED_SHORT, or UNSIGNED_INT. The error INVALID_OPERATION is generated by TexImage2D if <format> and <internalformat> are DEPTH_STENCIL_OES and <type> is not UNSIGNED_INT_24_8_OES. The error INVALID_OPERATION is generated by TexSubImage2D if <format> is DEPTH_STENCIL_OES and <type> is not UNSIGNED_INT_24_8_OES. The error INVALID_OPERATION is generated by TexImage2D if <format> and <internalformat> is not DEPTH_STENCIL_OES and <type> is UNSIGNED_INT_24_8_OES. The error INVALID_OPERATION is generated by TexSubImage2D if <format> is not DEPTH_STENCIL_OES and <type> is UNSIGNED_INT_24_8_OES. The error INVALID_OPERATION is generated in the following situations: - TexImage2D is called with <format> and <internalformat> of DEPTH_COMPONENT or DEPTH_STENCIL_OES and - <target> is not TEXTURE_2D, - <data> is not NULL, or - <level> is not zero. - TexSubImage2D is called with <format> of DEPTH_COMPONENT or DEPTH_STENCIL_OES. - TexStorage2DEXT is called with <internalformat> of DEPTH_COMPONENT16, DEPTH_COMPONENT32_OES, or DEPTH24_STENCIL8_OES, and - <target> is not TEXTURE_2D, or - <levels> is not one. - CopyTexImage2D is called with an <internalformat> that has a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES. - CopyTexSubImage2D is called with a target texture that has a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES. - GenerateMipmap is called on a texture that has a base internal format of DEPTH_COMPONENT or DEPTH_STENCIL_OES. New State None. Issues 1) What are the differences between this extension and OES_depth_texture and OES_packed_depth_stencil? RESOLVED: This extension: - does not support loading pre-baked depth stencil data via TexImage2D or TexSubImage2D. - allows variability in the y-, z-, and w-components of the sample results from depth textures. - only supports one level textures. - explicitly lists the errors for unsupported functionality. Since these were not clearly specified in the OES_depth_texture extension there may be differences in error values between implementations of OES_depth_texture and ANGLE_depth_texture. This specification was also rebased to apply against the OpenGL ES 2.0 specification instead of the OpenGL specification, making it more obvious what all the functionality changes are. 2) Why does TexSubImage2D accept the new format/type combinations even though it does not actually support loading data? RESOLVED: This was done to be more consistent with the OES_depth_texture extension and to make it easier to add support for loading texture data if it is possible to support in the future. 3) Why are only 1-level depth textures supported? RESOLVED: The only use for multiple levels of depth textures would be for fitlered texturing. However since it is not possible to render to non-zero-level texture levels in OpenGL ES 2.0, and since this extension forbids loading existing data and GenerateMipmap on depth textures, it is impossible to initialize or specify contents for non-zero levels of depth textures. Revision History 02/25/2013 swoods revise to allow texture lookup to guarantee depth values only in red channel of sample result. 06/04/2012 dgkoch fix errors, disallow multi-level depth textures. 05/30/2012 dgkoch minor updates and add issues. 05/23/2012 dgkoch intial revision based on OES_depth_texture and OES_packed_depth_stencil and rebased against the ES 2.0 spec