| Name |
| |
| EXT_texture_rg |
| |
| Name Strings |
| |
| GL_EXT_texture_rg |
| |
| Contributors |
| |
| Contributors to ARB_texture_rg, on which this extension is based |
| Kyle Haughey |
| Richard Schreyer |
| |
| Contact |
| |
| Benj Lipchak, Apple (lipchak 'at' apple.com) |
| |
| Status |
| |
| Complete |
| |
| Version |
| |
| Date: July 22, 2011 |
| Revision: 3 |
| |
| Number |
| |
| OpenGL ES Extension #103 |
| |
| Dependencies |
| |
| Requires OpenGL ES 2.0. |
| |
| Written based on the wording of the OpenGL ES 2.0.25 Full Specification |
| (November 2, 2010). |
| |
| OES_texture_float affects the definition of this extension. |
| |
| OES_texture_half_float affects the definition of this extension. |
| |
| APPLE_framebuffer_multisample affects the definition of this extension. |
| |
| Overview |
| |
| Historically one- and two-component textures have been specified in OpenGL |
| ES using the luminance or luminance-alpha (L/LA) formats. With the advent |
| of programmable shaders and render-to-texture capabilities these legacy |
| formats carry some historical artifacts which are no longer useful. |
| |
| For example, when sampling from such textures, the luminance values are |
| replicated across the color components. This is no longer necessary with |
| programmable shaders. |
| |
| It is also desirable to be able to render to one- and two-component format |
| textures using capabilities such as framebuffer objects (FBO), but |
| rendering to L/LA formats is under-specified (specifically how to map |
| R/G/B/A values to L/A texture channels). |
| |
| This extension adds new base internal formats for one-component RED and |
| two-component RG (red green) textures as well as sized RED and RG internal |
| formats for renderbuffers. The RED and RG texture formats can be used for |
| both texturing and rendering into with framebuffer objects. |
| |
| New Procedures and Functions |
| |
| None |
| |
| New Tokens |
| |
| Accepted by the <internalformat> parameter of TexImage2D and CopyTexImage2D, |
| and the <format> parameter of TexImage2D, TexSubImage2D, and ReadPixels: |
| |
| RED_EXT 0x1903 |
| RG_EXT 0x8227 |
| |
| Accepted by the <internalformat> parameter of RenderbufferStorage and |
| RenderbufferStorageMultisampleAPPLE: |
| |
| R8_EXT 0x8229 |
| RG8_EXT 0x822B |
| |
| Additions to Chapter 2 of the OpenGL ES 2.0 Specification (OpenGL ES Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the OpenGL ES 2.0 Specification (Rasterization) |
| |
| (Add the following to Table 3.3: "TexImage2D and ReadPixels formats") |
| |
| Format Name Element Meaning and Order Target Buffer |
| ----------- ------------------------- ------------- |
| RED_EXT R Color |
| RG_EXT R, G Color |
| |
| (Add the following to Table 3.4: "Valid pixel format and type combinations") |
| (as modified by OES_texture_float and OES_texture_half_float) |
| |
| Format Type Bytes per Pixel |
| ----------- ------------------------- --------------- |
| RED_EXT FLOAT 4 |
| RED_EXT HALF_FLOAT_OES 2 |
| RED_EXT UNSIGNED_BYTE 1 |
| RG_EXT FLOAT 8 |
| RG_EXT HALF_FLOAT_OES 4 |
| RG_EXT UNSIGNED_BYTE 2 |
| |
| (Add the following to Table 3.8: "Conversion from RGBA and depth pixel |
| components to internal texture") |
| |
| Base Internal Format RGBA Internal Components |
| -------------------- ------ ------------------- |
| RED_EXT R R |
| RG_EXT R,G R,G |
| |
| (Modify Table 3.9: "CopyTexImage internal format/color buffer combinations") |
| |
| Texture Format |
| Color Buffer A L LA R RG RGB RGBA |
| ------------ - - -- - -- --- ---- |
| A X |
| R X X |
| RG X X X |
| RGB X X X X |
| RGBA X X X X X X X |
| |
| (Add the following to Table 3.12: "Correspondence of filtered texture |
| components to texture source color components") |
| |
| Texture Base Texture source color |
| Internal Format C_s A_s |
| --------------- ------------- ------ |
| RED_EXT (R_t, 0, 0) 1 |
| RG_EXT (R_t, G_t, 0) 1 |
| |
| Additions to Chapter 4 of the OpenGL ES 2.0 Specification (Per-Fragment |
| Operations and the Framebuffer) |
| |
| In section 4.3.1 "Reading Pixels", subsection "Obtaining Pixels from the |
| Framebuffer", modify the last sentence to read: |
| |
| "If the framebuffer does not support G, B, or A values then the G, B, and A |
| values that are obtained are 0.0, 0.0, and 1.0 respectively." |
| |
| In section 4.4.5 "Framebuffer Completeness", modify the last sentence of |
| the second paragraph to read: |
| |
| "Color-renderable formats contain red, and possibly green, blue, and alpha |
| components; depth-renderable formats contain depth components; and |
| stencil-renderable formats contain stencil components." |
| |
| (Add the following to Table 4.5: "Renderbuffer image formats, showing their |
| renderable type (color-, depth-, or stencil-renderable) and the number of |
| bits each format contains for color (R, G, B, A), depth (D), and stencil |
| (S) components") |
| |
| Sized Internal Renderable Type R bits G bits B bits A bits D bits S bits |
| Format |
| -------------- ---------------- ------ ------ ------ ------ ------ ------ |
| R8_EXT color-renderable 8 |
| RG8_EXT color-renderable 8 8 |
| |
| Additions to Chapter 5 of the OpenGL ES 2.0 Specification (Special Functions) |
| |
| None |
| |
| Additions to Chapter 6 of the OpenGL ES 2.0 Specification (State and State |
| Requests) |
| |
| None |
| |
| Dependencies on OES_texture_float |
| |
| If OES_texture_float is not supported, then omit the rows of |
| Table 3.4 that have Type FLOAT. |
| |
| Dependencies on OES_texture_half_float |
| |
| If OES_texture_half_float is not supported, then omit the rows of |
| Table 3.4 that have Type HALF_FLOAT_OES. |
| |
| Dependencies on APPLE_framebuffer_multisample |
| |
| If APPLE_framebuffer_multisample is not supported, then all references to |
| RenderbufferStorageMultisampleAPPLE should be ignored. |
| |
| Revision History |
| |
| #1 February 22, 2011, khaughey |
| - initial version adapted from ARB_texture_rg. |
| #2 June 16, 2011, benj |
| - add interaction with APPLE_framebuffer_multisample |
| #3 July 22, 2011, benj |
| - rename from APPLE to EXT |
