1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/angle/extensions/ANGLE_texture_compression_dxt.txt Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,163 @@
1.4 +Name
1.5 +
1.6 + ANGLE_texture_compression_dxt
1.7 +
1.8 +Name Strings
1.9 +
1.10 + GL_ANGLE_texture_compression_dxt1
1.11 + GL_ANGLE_texture_compression_dxt3
1.12 + GL_ANGLE_texture_compression_dxt5
1.13 +
1.14 +Contributors
1.15 +
1.16 + Gregg Tavares, Google Inc.
1.17 + Daniel Koch, TransGaming Inc.
1.18 + Al Patrick, Google Inc.
1.19 +
1.20 +Contacts
1.21 +
1.22 + Gregg Tavares, Google Inc. (gman 'at' google 'dot' com)
1.23 +
1.24 +Status
1.25 +
1.26 + Implemented in ANGLE ES2
1.27 +
1.28 +Version
1.29 +
1.30 + Last Modified Date: Sept 22, 2012
1.31 + Author Revision: 2
1.32 +
1.33 +Number
1.34 +
1.35 + OpenGL ES Extension #111
1.36 +
1.37 +Dependencies
1.38 +
1.39 + Requires OpenGL ES 1.0.
1.40 +
1.41 + The extension is written against the OpenGL ES 2.0 specification.
1.42 +
1.43 +Overview
1.44 +
1.45 + These extensions are exactly the same as EXT_texture_compression_dxt1
1.46 + except they additionally expose the COMPRESSED_RGBA_S3TC_DXT3_ANGLE and
1.47 + COMPRESSED_RGBA_S3TC_DXT5_ANGLE formats and have a size restrictions
1.48 + such that the size must be a multiple of four (except for mip levels
1.49 + where the dimensions are either 2 or 1).
1.50 +
1.51 + See EXT_texture_compression_dxt1 for the full list of changes. Also
1.52 + see EXT_texture_compression_s3tc for a description of the formats.
1.53 +
1.54 +IP Status
1.55 +
1.56 + A license to the S3TC Intellectual Property may be necessary for
1.57 + implementation of this extension. You should consult with your
1.58 + Attorney to determine the need for a license.
1.59 +
1.60 +New Procedures and Functions
1.61 +
1.62 + None.
1.63 +
1.64 +New Types
1.65 +
1.66 + None.
1.67 +
1.68 +New Tokens
1.69 +
1.70 + Accepted by the <internalformat> parameter of CompressedTexImage2D
1.71 + and the <format> parameter of CompressedTexSubImage2D:
1.72 +
1.73 + COMPRESSED_RGB_S3TC_DXT1_ANGLE 0x83F0
1.74 + COMPRESSED_RGBA_S3TC_DXT1_ANGLE 0x83F1
1.75 + COMPRESSED_RGBA_S3TC_DXT3_ANGLE 0x83F2
1.76 + COMPRESSED_RGBA_S3TC_DXT5_ANGLE 0x83F3
1.77 +
1.78 +Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
1.79 +
1.80 + Add the following to Section 3.7.3 (Compressed Texture Images)
1.81 + (at the end of the description of the CompressedTexImage2D command):
1.82 +
1.83 + Compressed Internal Format Base Internal Format
1.84 + ========================== ====================
1.85 + COMPRESSED_RGB_S3TC_DXT1_ANGLE RGB
1.86 + COMPRESSED_RGBA_S3TC_DXT1_ANGLE RGBA
1.87 + COMPRESSED_RGBA_S3TC_DXT3_ANGLE RGBA
1.88 + COMPRESSED_RGBA_S3TC_DXT5_ANGLE RGBA
1.89 +
1.90 + Table 3.x: Specific Compressed Internal Formats
1.91 +
1.92 + If <internalformat> is one of the S3TC formats listed in Table 3.x,
1.93 + the compressed texture is stored in the appropriate S3TC compressed
1.94 + texture format (see Appendix). The GL and the S3TC texture compression
1.95 + algorithm support only 2D images without borders.
1.96 +
1.97 + CompressedTexImage2D will produce the INVALID_OPERATION error when
1.98 + <internalformat> is one of the values from Table 3.x under the following
1.99 + conditions:
1.100 +
1.101 + * <border> is non-zero.
1.102 + * <width> is not one, two, or a multiple of four.
1.103 + * <height> is not one, two, or a multiple of four.
1.104 +
1.105 + Add the following to Section 3.7.3 (Compressed Texture Images)
1.106 + (at the end of the description of the CompressedTexSubImage2D command):
1.107 +
1.108 + If the internal format of the texture image being modified is listed
1.109 + in Table 3.x, the texture is stored in the appropriate S3TC compressed
1.110 + texture format (see Appendix). Since DXT/S3TC images are easily edited
1.111 + along 4x4 texel boundaries, the limitations of CompressedTexSubImage2D
1.112 + are relaxed. CompressedTexSubImage2D will result in an INVALID_OPERATION
1.113 + error only if one of the following conditions occurs:
1.114 +
1.115 + * <width> is not a multiple of four or equal to TEXTURE_WIDTH.
1.116 + * <height> is not a multipls of four or equal to TEXTURE_HEIGHT.
1.117 + * <xoffset> or <yoffset> is not a multiple of four.
1.118 + * <format> does not match the internal format of the texture image
1.119 + being modified.
1.120 +
1.121 + The following restrictions at the end of section 3.7.3 do not apply
1.122 + to S3TC DXT texture formats, since subimage modification is straightforward
1.123 + as long as the subimage is properly aligned.
1.124 +
1.125 +Errors
1.126 +
1.127 + INVALID_OPERATION is generated by CompressedTexImage2D if <internalformat>
1.128 + is one of the compressed internal formats from Table 3.x and any of the
1.129 + following apply:
1.130 + - <border> is not equal to zero.
1.131 + - <width> is not one, two, or a multiple of four.
1.132 + - <height> is not one, two, or a multiple of four.
1.133 +
1.134 + INVALID_OPERATION is generated by TexImage2D and CopyTexImage2D if
1.135 + <internalformat> is one of the compressed internal formats from
1.136 + Table 3.x.
1.137 +
1.138 + INVALID_OPERATION is generated by TexSubImage2D and CopyTexSubImage2D
1.139 + if the internal format of the texture currently bound to <target> is
1.140 + one of the compressed internal formats from Table 3.x.
1.141 +
1.142 + INVALID_OPERATION is generated by CompressedTexSubImage2D if <format>
1.143 + is one of the compressed interal formats from Table 3.x and any of the
1.144 + following apply:
1.145 + - <width> is not a multiple of four or equal to TEXTURE_WIDTH;
1.146 + - <height> is not a multiple of four or equal to TEXTURE_HEIGHT;
1.147 + - <xoffset> or <yoffset> is not a multiple of four;
1.148 + - <format> does not match the internal format of the texture image
1.149 + being modified.
1.150 +
1.151 +New State
1.152 +
1.153 + None.
1.154 +
1.155 +Appendix:
1.156 +
1.157 + The format for the S3TC Compressed Texture Images Formats is documented
1.158 + in the appendix of EXT_texture_compression_s3tc.
1.159 +
1.160 +Revision History
1.161 +
1.162 + Revision 1, 2010/08/06 - gman
1.163 + - Initial revision
1.164 + Revision 2, 2012/09/22 - dgkoch
1.165 + - Added DXT1 formats and documented multiple of 4 restriction.
1.166 +
