Geoff Lang | 632192d | 2013-10-04 13:40:46 -0400 | [diff] [blame] | 1 | Name |
| 2 | |
| 3 | EXT_texture_rg |
| 4 | |
| 5 | Name Strings |
| 6 | |
| 7 | GL_EXT_texture_rg |
| 8 | |
| 9 | Contributors |
| 10 | |
| 11 | Contributors to ARB_texture_rg, on which this extension is based |
| 12 | Kyle Haughey |
| 13 | Richard Schreyer |
| 14 | |
| 15 | Contact |
| 16 | |
| 17 | Benj Lipchak, Apple (lipchak 'at' apple.com) |
| 18 | |
| 19 | Status |
| 20 | |
| 21 | Complete |
| 22 | |
| 23 | Version |
| 24 | |
| 25 | Date: July 22, 2011 |
| 26 | Revision: 3 |
| 27 | |
| 28 | Number |
| 29 | |
| 30 | OpenGL ES Extension #103 |
| 31 | |
| 32 | Dependencies |
| 33 | |
| 34 | Requires OpenGL ES 2.0. |
| 35 | |
| 36 | Written based on the wording of the OpenGL ES 2.0.25 Full Specification |
| 37 | (November 2, 2010). |
| 38 | |
| 39 | OES_texture_float affects the definition of this extension. |
| 40 | |
| 41 | OES_texture_half_float affects the definition of this extension. |
| 42 | |
| 43 | APPLE_framebuffer_multisample affects the definition of this extension. |
| 44 | |
| 45 | Overview |
| 46 | |
| 47 | Historically one- and two-component textures have been specified in OpenGL |
| 48 | ES using the luminance or luminance-alpha (L/LA) formats. With the advent |
| 49 | of programmable shaders and render-to-texture capabilities these legacy |
| 50 | formats carry some historical artifacts which are no longer useful. |
| 51 | |
| 52 | For example, when sampling from such textures, the luminance values are |
| 53 | replicated across the color components. This is no longer necessary with |
| 54 | programmable shaders. |
| 55 | |
| 56 | It is also desirable to be able to render to one- and two-component format |
| 57 | textures using capabilities such as framebuffer objects (FBO), but |
| 58 | rendering to L/LA formats is under-specified (specifically how to map |
| 59 | R/G/B/A values to L/A texture channels). |
| 60 | |
| 61 | This extension adds new base internal formats for one-component RED and |
| 62 | two-component RG (red green) textures as well as sized RED and RG internal |
| 63 | formats for renderbuffers. The RED and RG texture formats can be used for |
| 64 | both texturing and rendering into with framebuffer objects. |
| 65 | |
| 66 | New Procedures and Functions |
| 67 | |
| 68 | None |
| 69 | |
| 70 | New Tokens |
| 71 | |
| 72 | Accepted by the <internalformat> parameter of TexImage2D and CopyTexImage2D, |
| 73 | and the <format> parameter of TexImage2D, TexSubImage2D, and ReadPixels: |
| 74 | |
| 75 | RED_EXT 0x1903 |
| 76 | RG_EXT 0x8227 |
| 77 | |
| 78 | Accepted by the <internalformat> parameter of RenderbufferStorage and |
| 79 | RenderbufferStorageMultisampleAPPLE: |
| 80 | |
| 81 | R8_EXT 0x8229 |
| 82 | RG8_EXT 0x822B |
| 83 | |
| 84 | Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL ES Operation) |
| 85 | |
| 86 | None |
| 87 | |
| 88 | Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization) |
| 89 | |
| 90 | (Add the following to Table 3.3: "TexImage2D and ReadPixels formats") |
| 91 | |
| 92 | Format Name Element Meaning and Order Target Buffer |
| 93 | ----------- ------------------------- ------------- |
| 94 | RED_EXT R Color |
| 95 | RG_EXT R, G Color |
| 96 | |
| 97 | (Add the following to Table 3.4: "Valid pixel format and type combinations") |
| 98 | (as modified by OES_texture_float and OES_texture_half_float) |
| 99 | |
| 100 | Format Type Bytes per Pixel |
| 101 | ----------- ------------------------- --------------- |
| 102 | RED_EXT FLOAT 4 |
| 103 | RED_EXT HALF_FLOAT_OES 2 |
| 104 | RED_EXT UNSIGNED_BYTE 1 |
| 105 | RG_EXT FLOAT 8 |
| 106 | RG_EXT HALF_FLOAT_OES 4 |
| 107 | RG_EXT UNSIGNED_BYTE 2 |
| 108 | |
| 109 | (Add the following to Table 3.8: "Conversion from RGBA and depth pixel |
| 110 | components to internal texture") |
| 111 | |
| 112 | Base Internal Format RGBA Internal Components |
| 113 | -------------------- ------ ------------------- |
| 114 | RED_EXT R R |
| 115 | RG_EXT R,G R,G |
| 116 | |
| 117 | (Modify Table 3.9: "CopyTexImage internal format/color buffer combinations") |
| 118 | |
| 119 | Texture Format |
| 120 | Color Buffer A L LA R RG RGB RGBA |
| 121 | ------------ - - -- - -- --- ---- |
| 122 | A X |
| 123 | R X X |
| 124 | RG X X X |
| 125 | RGB X X X X |
| 126 | RGBA X X X X X X X |
| 127 | |
| 128 | (Add the following to Table 3.12: "Correspondence of filtered texture |
| 129 | components to texture source color components") |
| 130 | |
| 131 | Texture Base Texture source color |
| 132 | Internal Format C_s A_s |
| 133 | --------------- ------------- ------ |
| 134 | RED_EXT (R_t, 0, 0) 1 |
| 135 | RG_EXT (R_t, G_t, 0) 1 |
| 136 | |
| 137 | Additions to Chapter 4 of the OpenGL ES 2.0 Specification (Per-Fragment |
| 138 | Operations and the Framebuffer) |
| 139 | |
| 140 | In section 4.3.1 "Reading Pixels", subsection "Obtaining Pixels from the |
| 141 | Framebuffer", modify the last sentence to read: |
| 142 | |
| 143 | "If the framebuffer does not support G, B, or A values then the G, B, and A |
| 144 | values that are obtained are 0.0, 0.0, and 1.0 respectively." |
| 145 | |
| 146 | In section 4.4.5 "Framebuffer Completeness", modify the last sentence of |
| 147 | the second paragraph to read: |
| 148 | |
| 149 | "Color-renderable formats contain red, and possibly green, blue, and alpha |
| 150 | components; depth-renderable formats contain depth components; and |
| 151 | stencil-renderable formats contain stencil components." |
| 152 | |
| 153 | (Add the following to Table 4.5: "Renderbuffer image formats, showing their |
| 154 | renderable type (color-, depth-, or stencil-renderable) and the number of |
| 155 | bits each format contains for color (R, G, B, A), depth (D), and stencil |
| 156 | (S) components") |
| 157 | |
| 158 | Sized Internal Renderable Type R bits G bits B bits A bits D bits S bits |
| 159 | Format |
| 160 | -------------- ---------------- ------ ------ ------ ------ ------ ------ |
| 161 | R8_EXT color-renderable 8 |
| 162 | RG8_EXT color-renderable 8 8 |
| 163 | |
| 164 | Additions to Chapter 5 of the OpenGL ES 2.0 Specification (Special Functions) |
| 165 | |
| 166 | None |
| 167 | |
| 168 | Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State |
| 169 | Requests) |
| 170 | |
| 171 | None |
| 172 | |
| 173 | Dependencies on OES_texture_float |
| 174 | |
| 175 | If OES_texture_float is not supported, then omit the rows of |
| 176 | Table 3.4 that have Type FLOAT. |
| 177 | |
| 178 | Dependencies on OES_texture_half_float |
| 179 | |
| 180 | If OES_texture_half_float is not supported, then omit the rows of |
| 181 | Table 3.4 that have Type HALF_FLOAT_OES. |
| 182 | |
| 183 | Dependencies on APPLE_framebuffer_multisample |
| 184 | |
| 185 | If APPLE_framebuffer_multisample is not supported, then all references to |
| 186 | RenderbufferStorageMultisampleAPPLE should be ignored. |
| 187 | |
| 188 | Revision History |
| 189 | |
| 190 | #1 February 22, 2011, khaughey |
| 191 | - initial version adapted from ARB_texture_rg. |
| 192 | #2 June 16, 2011, benj |
| 193 | - add interaction with APPLE_framebuffer_multisample |
| 194 | #3 July 22, 2011, benj |
| 195 | - rename from APPLE to EXT |