зеркало из https://github.com/AvaloniaUI/angle.git
164 строки
5.4 KiB
Plaintext
164 строки
5.4 KiB
Plaintext
Name
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ANGLE_texture_compression_dxt
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Name Strings
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GL_ANGLE_texture_compression_dxt1
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GL_ANGLE_texture_compression_dxt3
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GL_ANGLE_texture_compression_dxt5
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Contributors
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Gregg Tavares, Google Inc.
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Daniel Koch, TransGaming Inc.
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Al Patrick, Google Inc.
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Contacts
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Gregg Tavares, Google Inc. (gman 'at' google 'dot' com)
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Status
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Implemented in ANGLE ES2
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Version
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Last Modified Date: Sept 22, 2012
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Author Revision: 2
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Number
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OpenGL ES Extension #111
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Dependencies
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Requires OpenGL ES 1.0.
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The extension is written against the OpenGL ES 2.0 specification.
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Overview
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These extensions are exactly the same as EXT_texture_compression_dxt1
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except they additionally expose the COMPRESSED_RGBA_S3TC_DXT3_ANGLE and
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COMPRESSED_RGBA_S3TC_DXT5_ANGLE formats and have a size restrictions
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such that the size must be a multiple of four (except for mip levels
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where the dimensions are either 2 or 1).
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See EXT_texture_compression_dxt1 for the full list of changes. Also
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see EXT_texture_compression_s3tc for a description of the formats.
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IP Status
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A license to the S3TC Intellectual Property may be necessary for
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implementation of this extension. You should consult with your
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Attorney to determine the need for a license.
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New Procedures and Functions
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None.
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New Types
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None.
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New Tokens
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Accepted by the <internalformat> parameter of CompressedTexImage2D
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and the <format> parameter of CompressedTexSubImage2D:
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COMPRESSED_RGB_S3TC_DXT1_ANGLE 0x83F0
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COMPRESSED_RGBA_S3TC_DXT1_ANGLE 0x83F1
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COMPRESSED_RGBA_S3TC_DXT3_ANGLE 0x83F2
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COMPRESSED_RGBA_S3TC_DXT5_ANGLE 0x83F3
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Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
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Add the following to Section 3.7.3 (Compressed Texture Images)
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(at the end of the description of the CompressedTexImage2D command):
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Compressed Internal Format Base Internal Format
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========================== ====================
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COMPRESSED_RGB_S3TC_DXT1_ANGLE RGB
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COMPRESSED_RGBA_S3TC_DXT1_ANGLE RGBA
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COMPRESSED_RGBA_S3TC_DXT3_ANGLE RGBA
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COMPRESSED_RGBA_S3TC_DXT5_ANGLE RGBA
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Table 3.x: Specific Compressed Internal Formats
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If <internalformat> is one of the S3TC formats listed in Table 3.x,
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the compressed texture is stored in the appropriate S3TC compressed
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texture format (see Appendix). The GL and the S3TC texture compression
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algorithm support only 2D images without borders.
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CompressedTexImage2D will produce the INVALID_OPERATION error when
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<internalformat> is one of the values from Table 3.x under the following
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conditions:
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* <border> is non-zero.
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* <width> is not one, two, or a multiple of four.
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* <height> is not one, two, or a multiple of four.
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Add the following to Section 3.7.3 (Compressed Texture Images)
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(at the end of the description of the CompressedTexSubImage2D command):
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If the internal format of the texture image being modified is listed
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in Table 3.x, the texture is stored in the appropriate S3TC compressed
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texture format (see Appendix). Since DXT/S3TC images are easily edited
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along 4x4 texel boundaries, the limitations of CompressedTexSubImage2D
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are relaxed. CompressedTexSubImage2D will result in an INVALID_OPERATION
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error only if one of the following conditions occurs:
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* <width> is not a multiple of four or equal to TEXTURE_WIDTH.
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* <height> is not a multipls of four or equal to TEXTURE_HEIGHT.
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* <xoffset> or <yoffset> is not a multiple of four.
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* <format> does not match the internal format of the texture image
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being modified.
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The following restrictions at the end of section 3.7.3 do not apply
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to S3TC DXT texture formats, since subimage modification is straightforward
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as long as the subimage is properly aligned.
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Errors
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INVALID_OPERATION is generated by CompressedTexImage2D if <internalformat>
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is one of the compressed internal formats from Table 3.x and any of the
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following apply:
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- <border> is not equal to zero.
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- <width> is not one, two, or a multiple of four.
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- <height> is not one, two, or a multiple of four.
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INVALID_OPERATION is generated by TexImage2D and CopyTexImage2D if
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<internalformat> is one of the compressed internal formats from
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Table 3.x.
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INVALID_OPERATION is generated by TexSubImage2D and CopyTexSubImage2D
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if the internal format of the texture currently bound to <target> is
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one of the compressed internal formats from Table 3.x.
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INVALID_OPERATION is generated by CompressedTexSubImage2D if <format>
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is one of the compressed interal formats from Table 3.x and any of the
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following apply:
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- <width> is not a multiple of four or equal to TEXTURE_WIDTH;
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- <height> is not a multiple of four or equal to TEXTURE_HEIGHT;
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- <xoffset> or <yoffset> is not a multiple of four;
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- <format> does not match the internal format of the texture image
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being modified.
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New State
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None.
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Appendix:
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The format for the S3TC Compressed Texture Images Formats is documented
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in the appendix of EXT_texture_compression_s3tc.
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Revision History
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Revision 1, 2010/08/06 - gman
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- Initial revision
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Revision 2, 2012/09/22 - dgkoch
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- Added DXT1 formats and documented multiple of 4 restriction.
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