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comparison: gfx/angle/extensions/ANGLE_texture_compression_dxt.txt

gfx/angle/extensions/ANGLE_texture_compression_dxt.txt

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1 Name
2
3 ANGLE_texture_compression_dxt
4
5 Name Strings
6
7 GL_ANGLE_texture_compression_dxt1
8 GL_ANGLE_texture_compression_dxt3
9 GL_ANGLE_texture_compression_dxt5
10
11 Contributors
12
13 Gregg Tavares, Google Inc.
14 Daniel Koch, TransGaming Inc.
15 Al Patrick, Google Inc.
16
17 Contacts
18
19 Gregg Tavares, Google Inc. (gman 'at' google 'dot' com)
20
21 Status
22
23 Implemented in ANGLE ES2
24
25 Version
26
27 Last Modified Date: Sept 22, 2012
28 Author Revision: 2
29
30 Number
31
32 OpenGL ES Extension #111
33
34 Dependencies
35
36 Requires OpenGL ES 1.0.
37
38 The extension is written against the OpenGL ES 2.0 specification.
39
40 Overview
41
42 These extensions are exactly the same as EXT_texture_compression_dxt1
43 except they additionally expose the COMPRESSED_RGBA_S3TC_DXT3_ANGLE and
44 COMPRESSED_RGBA_S3TC_DXT5_ANGLE formats and have a size restrictions
45 such that the size must be a multiple of four (except for mip levels
46 where the dimensions are either 2 or 1).
47
48 See EXT_texture_compression_dxt1 for the full list of changes. Also
49 see EXT_texture_compression_s3tc for a description of the formats.
50
51 IP Status
52
53 A license to the S3TC Intellectual Property may be necessary for
54 implementation of this extension. You should consult with your
55 Attorney to determine the need for a license.
56
57 New Procedures and Functions
58
59 None.
60
61 New Types
62
63 None.
64
65 New Tokens
66
67 Accepted by the <internalformat> parameter of CompressedTexImage2D
68 and the <format> parameter of CompressedTexSubImage2D:
69
70 COMPRESSED_RGB_S3TC_DXT1_ANGLE 0x83F0
71 COMPRESSED_RGBA_S3TC_DXT1_ANGLE 0x83F1
72 COMPRESSED_RGBA_S3TC_DXT3_ANGLE 0x83F2
73 COMPRESSED_RGBA_S3TC_DXT5_ANGLE 0x83F3
74
75 Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization)
76
77 Add the following to Section 3.7.3 (Compressed Texture Images)
78 (at the end of the description of the CompressedTexImage2D command):
79
80 Compressed Internal Format Base Internal Format
81 ========================== ====================
82 COMPRESSED_RGB_S3TC_DXT1_ANGLE RGB
83 COMPRESSED_RGBA_S3TC_DXT1_ANGLE RGBA
84 COMPRESSED_RGBA_S3TC_DXT3_ANGLE RGBA
85 COMPRESSED_RGBA_S3TC_DXT5_ANGLE RGBA
86
87 Table 3.x: Specific Compressed Internal Formats
88
89 If <internalformat> is one of the S3TC formats listed in Table 3.x,
90 the compressed texture is stored in the appropriate S3TC compressed
91 texture format (see Appendix). The GL and the S3TC texture compression
92 algorithm support only 2D images without borders.
93
94 CompressedTexImage2D will produce the INVALID_OPERATION error when
95 <internalformat> is one of the values from Table 3.x under the following
96 conditions:
97
98 * <border> is non-zero.
99 * <width> is not one, two, or a multiple of four.
100 * <height> is not one, two, or a multiple of four.
101
102 Add the following to Section 3.7.3 (Compressed Texture Images)
103 (at the end of the description of the CompressedTexSubImage2D command):
104
105 If the internal format of the texture image being modified is listed
106 in Table 3.x, the texture is stored in the appropriate S3TC compressed
107 texture format (see Appendix). Since DXT/S3TC images are easily edited
108 along 4x4 texel boundaries, the limitations of CompressedTexSubImage2D
109 are relaxed. CompressedTexSubImage2D will result in an INVALID_OPERATION
110 error only if one of the following conditions occurs:
111
112 * <width> is not a multiple of four or equal to TEXTURE_WIDTH.
113 * <height> is not a multipls of four or equal to TEXTURE_HEIGHT.
114 * <xoffset> or <yoffset> is not a multiple of four.
115 * <format> does not match the internal format of the texture image
116 being modified.
117
118 The following restrictions at the end of section 3.7.3 do not apply
119 to S3TC DXT texture formats, since subimage modification is straightforward
120 as long as the subimage is properly aligned.
121
122 Errors
123
124 INVALID_OPERATION is generated by CompressedTexImage2D if <internalformat>
125 is one of the compressed internal formats from Table 3.x and any of the
126 following apply:
127 - <border> is not equal to zero.
128 - <width> is not one, two, or a multiple of four.
129 - <height> is not one, two, or a multiple of four.
130
131 INVALID_OPERATION is generated by TexImage2D and CopyTexImage2D if
132 <internalformat> is one of the compressed internal formats from
133 Table 3.x.
134
135 INVALID_OPERATION is generated by TexSubImage2D and CopyTexSubImage2D
136 if the internal format of the texture currently bound to <target> is
137 one of the compressed internal formats from Table 3.x.
138
139 INVALID_OPERATION is generated by CompressedTexSubImage2D if <format>
140 is one of the compressed interal formats from Table 3.x and any of the
141 following apply:
142 - <width> is not a multiple of four or equal to TEXTURE_WIDTH;
143 - <height> is not a multiple of four or equal to TEXTURE_HEIGHT;
144 - <xoffset> or <yoffset> is not a multiple of four;
145 - <format> does not match the internal format of the texture image
146 being modified.
147
148 New State
149
150 None.
151
152 Appendix:
153
154 The format for the S3TC Compressed Texture Images Formats is documented
155 in the appendix of EXT_texture_compression_s3tc.
156
157 Revision History
158
159 Revision 1, 2010/08/06 - gman
160 - Initial revision
161 Revision 2, 2012/09/22 - dgkoch
162 - Added DXT1 formats and documented multiple of 4 restriction.
163

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