| Name |
| |
| EXT_blend_minmax |
| |
| Name Strings |
| |
| GL_EXT_blend_minmax |
| |
| Version |
| |
| Last Modified Date: September 17, 2009 |
| Version: 1.5 |
| |
| Number |
| |
| OpenGL Extension #37 |
| OpenGL ES Extension #65 |
| |
| Dependencies |
| |
| There is an interaction with OpenGL ES. |
| |
| Overview |
| |
| Blending capability is extended by respecifying the entire blend |
| equation. While this document defines only two new equations, the |
| BlendEquationEXT procedure that it defines will be used by subsequent |
| extensions to define additional blending equations. |
| |
| The two new equations defined by this extension produce the minimum |
| (or maximum) color components of the source and destination colors. |
| Taking the maximum is useful for applications such as maximum projection |
| in medical imaging. |
| |
| Issues |
| |
| * I've prefixed the ADD token with FUNC, to indicate that the blend |
| equation includes the parameters specified by BlendFunc. (The min |
| and max equations don't.) Is this necessary? Is it too ugly? |
| Is there a better way to accomplish the same thing? |
| |
| New Procedures and Functions |
| |
| void BlendEquationEXT(enum mode); |
| |
| New Tokens |
| |
| Accepted by the <mode> parameter of BlendEquationEXT: |
| |
| FUNC_ADD_EXT 0x8006 |
| MIN_EXT 0x8007 |
| MAX_EXT 0x8008 |
| |
| Accepted by the <pname> parameter of GetBooleanv, GetIntegerv, |
| GetFloatv, and GetDoublev: |
| |
| BLEND_EQUATION_EXT 0x8009 |
| |
| Additions to Chapter 2 of the GL Specification (OpenGL Operation) |
| |
| None |
| |
| Additions to Chapter 3 of the GL Specification (Rasterization) |
| |
| None |
| |
| Additions to Chapter 4 of the GL Specification (Per-Fragment Operations |
| and the Framebuffer) |
| |
| The GL Specification defines a single blending equation. This |
| extension introduces a blend equation mode that is specified by calling |
| BlendEquationEXT with one of three enumerated values. The default |
| value FUNC_ADD_EXT specifies that the blending equation defined in |
| the GL Specification be used. This equation is |
| |
| C' = (Cs * S) + (Cd * D) |
| |
| / 1.0 C' > 1.0 |
| C = ( |
| \ C' C' <= 1.0 |
| |
| where Cs and Cd are the source and destination colors, and S and D are |
| as specified by BlendFunc. |
| |
| If BlendEquationEXT is called with <mode> set to MIN_EXT, the |
| blending equation becomes |
| |
| C = min (Cs, Cd) |
| |
| Finally, if BlendEquationEXT is called with <mode> set to MAX_EXT, the |
| blending equation becomes |
| |
| C = max (Cs, Cd) |
| |
| In all cases the blending equation is evaluated separately for each |
| color component. |
| |
| Additions to Chapter 5 of the GL Specification (Special Functions) |
| |
| None |
| |
| Additions to Chapter 6 of the GL Specification (State and State Requests) |
| |
| None |
| |
| Additions to the GLX Specification |
| |
| None |
| |
| GLX Protocol |
| |
| A new GL rendering command is added. The following command is sent to the |
| server as part of a glXRender request: |
| |
| BlendEquationEXT |
| 2 8 rendering command length |
| 2 4097 rendering command opcode |
| 4 ENUM mode |
| |
| Dependencies on OpenGL ES |
| |
| If the GL is OpenGL ES, only the new MIN_EXT and MAX_EXT blend equations |
| are introduced by this extension. BlendEquationOES, FUNC_ADD_OES, and |
| BLEND_EQUATION_OES are introduced by the OES_blend_subtract extension, |
| which is required for this extension to operate. Alternatively, |
| OpenGL ES 2.0 is required, which introduces BlendEquation, FUNC_ADD, and |
| BLEND_EQUATION without the suffixes. |
| |
| MIN_EXT and MAX_EXT should be added to Table 4.blendeq described in the |
| OES_blend_subtract extension specification, and Table 4.1 of the OpenGL |
| ES 2.0 specification. |
| |
| Mentions of GetDoublev, Begin/End, and GLX in this extension specification |
| can be ignored for OpenGL ES. Also, BlendEquationEXT and FUNC_ADD_EXT |
| instead have the OES suffix courtesy of OES_blend_subtract, or no suffix |
| courtesy of core OpenGL ES 2.0. |
| |
| Errors |
| |
| INVALID_ENUM is generated by BlendEquationEXT if its single parameter |
| is not FUNC_ADD_EXT, MIN_EXT, or MAX_EXT. |
| |
| INVALID_OPERATION is generated if BlendEquationEXT is executed between |
| the execution of Begin and the corresponding execution to End. |
| |
| New State |
| |
| Get Value Get Command Type Initial Value Attribute |
| --------- ----------- ---- ------------- --------- |
| BLEND_EQUATION_EXT GetIntegerv Z3 FUNC_ADD_EXT color-buffer |
| |
| New Implementation Dependent State |
| |
| None |
| |
| Revision History |
| |
| Version 1.5, September 17, 2009 (Jon Leech) - |
| Merge into OpenGL Registry version of the extension and assign |
| OpenGL ES extension number. |
| Version 1.4, May 19, 2009 (Benj Lipchak) - |
| Adapted for OpenGL ES. |
| Version 1.3, May 31, 1995 - |
| Last SGI revision. |
