| Name |
| |
| OES_blend_equation_separate |
| |
| Name Strings |
| |
| GL_OES_blend_equation_separate |
| |
| Contact |
| |
| Benj Lipchak, Apple (lipchak 'at' apple.com) |
| |
| Notice |
| |
| Copyright (c) 2009-2013 The Khronos Group Inc. Copyright terms at |
| http://www.khronos.org/registry/speccopyright.html |
| |
| Specification Update Policy |
| |
| Khronos-approved extension specifications are updated in response to |
| issues and bugs prioritized by the Khronos OpenGL ES Working Group. For |
| extensions which have been promoted to a core Specification, fixes will |
| first appear in the latest version of that core Specification, and will |
| eventually be backported to the extension document. This policy is |
| described in more detail at |
| https://www.khronos.org/registry/OpenGL/docs/update_policy.php |
| |
| Status |
| |
| Ratified by the Khronos BOP, July 31, 2009. |
| |
| Version |
| |
| Date: 06/17/2009 Version 1.1 |
| |
| Number |
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| OpenGL ES Extension #1 |
| |
| Dependencies |
| |
| Written based on the wording of the OpenGL ES 1.1 specification. |
| |
| OES_blend_subtract is required for blend equation support. |
| |
| Overview |
| |
| OpenGL ES 1.1 provides a single blend equation that applies to both RGB |
| and alpha portions of blending. This extension provides a separate blend |
| equation for RGB and alpha to match the generality available for blend |
| factors. |
| |
| New Procedures and Functions |
| |
| void BlendEquationSeparateOES(enum modeRGB, enum modeAlpha); |
| |
| New Tokens |
| |
| Accepted by the <pname> parameter of GetBooleanv, GetIntegerv, and |
| GetFloatv: |
| |
| BLEND_EQUATION_RGB_OES 0x8009 (same as BLEND_EQUATION_OES) |
| BLEND_EQUATION_ALPHA_OES 0x883D |
| |
| Additions to Chapter 2 of the OpenGL ES 1.1 Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the OpenGL ES 1.1 Specification (Rasterization) |
| |
| None |
| |
| Additions to Chapter 4 of the OpenGL ES 1.1 Specification (Per-Fragment Operations |
| and the Framebuffer) |
| |
| Replace the first paragraph of the "Blend Equation" discussion in section |
| 4.1.7 (Blending) with the following: |
| |
| "Blending is controlled by the blend equations, defined by the commands |
| |
| void BlendEquationOES(enum mode); |
| void BlendEquationSeparateOES(enum modeRGB, enum modeAlpha); |
| |
| BlendEquationSeparateOES argument <modeRGB> determines the RGB blend |
| equation while <modeAlpha> determines the alpha blend equation. |
| BlendEquationOES argument <mode> determines both the RGB and alpha blend |
| equations. <modeRGB> and <modeAlpha> must each be one of FUNC_ADD_OES, |
| FUNC_SUBTRACT_OES, or FUNC_REVERSE_SUBTRACT_OES. |
| |
| Replace the last paragraph of the "Blend Equation" discussion in section |
| 4.1.7 (Blending) with the following: |
| |
| Table 4.blendeq provides the corresponding per-component blend |
| equations for each mode, whether acting on RGB components for <modeRGB> |
| or the alpha component for <modeAlpha>. |
| |
| In the table, the "s" subscript on a color component abbreviation |
| (R, G, B, or A) refers to the source color component for an incoming |
| fragment and the "d" subscript on a color component abbreviation refers |
| to the destination color component at the corresponding framebuffer |
| location. A color component abbreviation without a subscript refers to |
| the new color component resulting from blending. Additionally, Sr, Sg, |
| Sb, and Sa are the red, green, blue, and alpha components of the source |
| weighting factors determined by the source blend function, and Dr, Dg, Db, |
| and Da are the red, green, blue, and alpha components of the destination |
| weighting factors determined by the destination blend function. Blend |
| functions are described below. |
| |
| Mode RGB components Alpha component |
| --------------------- ---------------------- ---------------------- |
| FUNC_ADD Rc = Rs * Sr + Rd * Dr Ac = As * Sa + Ad * Da |
| Gc = Gs * Sg + Gd * Dg |
| Bc = Bs * Sb + Bd * Db |
| --------------------- ---------------------- ---------------------- |
| FUNC_SUBTRACT Rc = Rs * Sr - Rd * Dr Ac = As * Sa - Ad * Da |
| Gc = Gs * Sg - Gd * Dg |
| Bc = Bs * Sb - Bd * Db |
| --------------------- ---------------------- ---------------------- |
| FUNC_REVERSE_SUBTRACT Rc = Rd * Sr - Rs * Dr Ac = Ad * Sa - As * Da |
| Gc = Gd * Sg - Gs * Dg |
| Bc = Bd * Sb - Bs * Db |
| --------------------- ---------------------- ---------------------- |
| |
| Table 4.blendeq: RGB and alpha blend equations." |
| |
| In the "Blending State" paragraph, insert the following in place of |
| existing blend equation state: |
| |
| "The state required for blending is... two integers indicating the RGB |
| and alpha blend equations... The initial blending equations for RGB and |
| alpha are FUNC_ADD_OES." |
| |
| Additions to Chapter 5 of the OpenGL ES 1.1 Specification (Special Functions) |
| |
| None |
| |
| Additions to Chapter 6 of the OpenGL ES 1.1 Specification (State and State Requests) |
| |
| None |
| |
| Errors |
| |
| INVALID_ENUM is generated if either the modeRGB or modeAlpha |
| parameter of BlendEquationSeparateOES is not one of FUNC_ADD_OES, |
| FUNC_SUBTRACT_OES, or FUNC_REVERSE_SUBTRACT_OES. |
| |
| New State |
| |
| Initial |
| Get Value Get Command Type Value |
| ------------------------ ----------- ---- ------------ |
| BLEND_EQUATION_RGB_OES GetIntegerv Z FUNC_ADD_OES |
| BLEND_EQUATION_ALPHA_OES GetIntegerv Z FUNC_ADD_OES |
| |
| [remove BLEND_EQUATION_OES from the table, add a note "BLEND_EQUATION_OES" |
| beside BLEND_EQUATION_RGB_OES to note the aliased name.] |
| |
| New Implementation Dependent State |
| |
| None |
| |
| Revision History |
| |
| 2009/06/17 Benj Lipchak Remove MIN/MAX from Table 4.blendeq |
| 2009/05/19 Benj Lipchak First draft of true extension specification |
| |
