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kc3-lang/angle/extensions/ANGLE_texture_compression_dxt.txt
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- extensions/ANGLE_texture_compression_dxt.txt
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Name ANGLE_texture_compression_dxt Name Strings GL_ANGLE_texture_compression_dxt1 GL_ANGLE_texture_compression_dxt3 GL_ANGLE_texture_compression_dxt5 Contributors Gregg Tavares, Google Inc. Daniel Koch, TransGaming Inc. Al Patrick, Google Inc. Contacts Gregg Tavares, Google Inc. (gman 'at' google 'dot' com) Status Implemented in ANGLE ES2 Version Last Modified Date: Sept 22, 2012 Author Revision: 2 Number OpenGL ES Extension #111 Dependencies Requires OpenGL ES 1.0. The extension is written against the OpenGL ES 2.0 specification. Overview These extensions are exactly the same as EXT_texture_compression_dxt1 except they additionally expose the COMPRESSED_RGBA_S3TC_DXT3_ANGLE and COMPRESSED_RGBA_S3TC_DXT5_ANGLE formats and have a size restrictions such that the size must be a multiple of four (except for mip levels where the dimensions are either 2 or 1). See EXT_texture_compression_dxt1 for the full list of changes. Also see EXT_texture_compression_s3tc for a description of the formats. IP Status A license to the S3TC Intellectual Property may be necessary for implementation of this extension. You should consult with your Attorney to determine the need for a license. New Procedures and Functions None. New Types None. New Tokens Accepted by the <internalformat> parameter of CompressedTexImage2D and the <format> parameter of CompressedTexSubImage2D: COMPRESSED_RGB_S3TC_DXT1_ANGLE 0x83F0 COMPRESSED_RGBA_S3TC_DXT1_ANGLE 0x83F1 COMPRESSED_RGBA_S3TC_DXT3_ANGLE 0x83F2 COMPRESSED_RGBA_S3TC_DXT5_ANGLE 0x83F3 Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization) Add the following to Section 3.7.3 (Compressed Texture Images) (at the end of the description of the CompressedTexImage2D command): Compressed Internal Format Base Internal Format ========================== ==================== COMPRESSED_RGB_S3TC_DXT1_ANGLE RGB COMPRESSED_RGBA_S3TC_DXT1_ANGLE RGBA COMPRESSED_RGBA_S3TC_DXT3_ANGLE RGBA COMPRESSED_RGBA_S3TC_DXT5_ANGLE RGBA Table 3.x: Specific Compressed Internal Formats If <internalformat> is one of the S3TC formats listed in Table 3.x, the compressed texture is stored in the appropriate S3TC compressed texture format (see Appendix). The GL and the S3TC texture compression algorithm support only 2D images without borders. CompressedTexImage2D will produce the INVALID_OPERATION error when <internalformat> is one of the values from Table 3.x under the following conditions: * <border> is non-zero. * <width> is not one, two, or a multiple of four. * <height> is not one, two, or a multiple of four. Add the following to Section 3.7.3 (Compressed Texture Images) (at the end of the description of the CompressedTexSubImage2D command): If the internal format of the texture image being modified is listed in Table 3.x, the texture is stored in the appropriate S3TC compressed texture format (see Appendix). Since DXT/S3TC images are easily edited along 4x4 texel boundaries, the limitations of 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 or equal to TEXTURE_WIDTH. * <height> is not a multipls of four or equal to TEXTURE_HEIGHT. * <xoffset> or <yoffset> is not a multiple of four. * <format> does not match the internal format of the texture image being modified. The following restrictions at the end of section 3.7.3 do not apply to S3TC DXT texture formats, since subimage modification is straightforward as long as the subimage is properly aligned. Errors INVALID_OPERATION is generated by CompressedTexImage2D if <internalformat> is one of the compressed internal formats from Table 3.x and any of the following apply: - <border> is not equal to zero. - <width> is not one, two, or a multiple of four. - <height> is not one, two, or a multiple of four. INVALID_OPERATION is generated by TexImage2D and CopyTexImage2D if <internalformat> is one of the compressed internal formats from Table 3.x. INVALID_OPERATION is generated by TexSubImage2D and CopyTexSubImage2D if the internal format of the texture currently bound to <target> is one of the compressed internal formats from Table 3.x. INVALID_OPERATION is generated by CompressedTexSubImage2D if <format> is one of the compressed interal formats from Table 3.x and any of the following apply: - <width> is not a multiple of four or equal to TEXTURE_WIDTH; - <height> is not a multiple of four or equal to TEXTURE_HEIGHT; - <xoffset> or <yoffset> is not a multiple of four; - <format> does not match the internal format of the texture image being modified. New State None. Appendix: The format for the S3TC Compressed Texture Images Formats is documented in the appendix of EXT_texture_compression_s3tc. Revision History Revision 1, 2010/08/06 - gman - Initial revision Revision 2, 2012/09/22 - dgkoch - Added DXT1 formats and documented multiple of 4 restriction.