| XXX - Not complete yet!!! But pretty close. |
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| Name |
| |
| SGIX_blend_alpha_minmax |
| |
| Name Strings |
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| GL_SGIX_blend_alpha_minmax |
| |
| Version |
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| $Date: 1998/03/31 00:55:21 $ $Revision: 1.3 $ |
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| Number |
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| 119 |
| |
| Dependencies |
| |
| EXT_blend_minmax is required |
| EXT_blend_subtract affects the number of values of BLEND_EQUATION_EXT |
| |
| Overview |
| |
| Two additional blending equations are specified using the interface |
| defined by EXT_blend_minmax. These equations are similar to the |
| MIN_EXT and MAX_EXT blending equations, but the outcome for all four |
| color components is determined by a comparison of just the alpha |
| component's source and destination values. These equations are useful |
| in image processing and advanced shading algorithms. |
| |
| New Procedures and Functions |
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| None |
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| New Tokens |
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| Accepted by the <mode> parameter of BlendEquationEXT: |
| |
| ALPHA_MIN_SGIX 0x8320 |
| ALPHA_MAX_SGIX 0x8321 |
| |
| Additions to Chapter 2 of the GL Specification (OpenGL Operation) |
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| None |
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| Additions to Chapter 3 of the GL Specification (Rasterization) |
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| None |
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| Additions to Chapter 4 of the GL Specification (Per-Fragment Operations |
| and the Framebuffer) |
| |
| Two additional blending equations are defined. If BlendEquationEXT is |
| called with <mode> set to ALPHA_MIN_EXT, the blending equation becomes |
| |
| / Cs As < Ad |
| C' = ( |
| \ Cd As >= Ad |
| |
| where C' is the color resulting from the blending operation, |
| Cs and Cd are the source and destination colors, and As and Ad |
| are the source and destination alpha in particular. |
| |
| If BlendEquationEXT is called with <mode> set to ALPHA_MAX_SGIX, the |
| blending equation becomes |
| |
| / Cs As > Ad |
| C' = ( |
| \ Cd As <= Ad |
| |
| In both cases the blending equation is evaluated separately for each |
| color component in a quadruplet. |
| |
| Additions to Chapter 5 of the GL Specification (Special Functions) |
| |
| None |
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| Additions to Chapter 6 of the GL Specification (State and State Requests) |
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| None |
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| Additions to the GLX Specification |
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| None |
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| GLX Protocol |
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| None |
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| Dependencies on EXT_blend_minmax |
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| EXT_blend_minmax is required. |
| |
| Errors |
| |
| INVALID_ENUM is generated by BlendEquationEXT if its single parameter |
| is not FUNC_ADD_EXT, MIN_EXT, MAX_EXT, FUNC_SUBTRACT_EXT, |
| FUNC_REVERSE_SUBTRACT_EXT, ALPHA_MIN_SGIX, or ALPHA_MAX_SGIX. |
| |
| INVALID_OPERATION is generated if BlendEquationEXT is executed between |
| the execution of Begin and the corresponding execution to End. |
| |
| New State |
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| Two new values of BLEND_EQUATION_EXT: |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| BLEND_EQUATION_EXT GetIntegerv Z7 FUNC_ADD_EXT color-buffer |
| |
| New Implementation Dependent State |
| |
| None |
