glBlendEquationSeparate — set the RGB blend equation and the alpha blend equation separately
void glBlendEquationSeparate(
|
GLenum modeRGB, |
GLenum modeAlpha); |
void glBlendEquationSeparatei(
|
GLuint buf, |
| GLenum modeRGB, | |
GLenum modeAlpha); |
buf
for glBlendEquationSeparatei, specifies the index of the draw buffer for which
to set the blend equations.
modeRGB
specifies the RGB blend equation, how the red, green, and blue components of the source and destination colors are combined.
It must be GL_FUNC_ADD, GL_FUNC_SUBTRACT,
GL_FUNC_REVERSE_SUBTRACT, GL_MIN, GL_MAX.
modeAlpha
specifies the alpha blend equation, how the alpha component of the source and destination colors are combined.
It must be GL_FUNC_ADD, GL_FUNC_SUBTRACT,
GL_FUNC_REVERSE_SUBTRACT, GL_MIN, GL_MAX.
The blend equations determines how a new pixel (the ''source'' color)
is combined with a pixel already in the framebuffer (the ''destination''
color). These functions specify one blend equation for the RGB-color
components and one blend equation for the alpha component. glBlendEquationSeparatei
specifies the blend equations for a single draw buffer whereas glBlendEquationSeparate
sets the blend equations for all draw buffers.
The blend equations use the source and destination blend factors specified by either glBlendFunc or glBlendFuncSeparate. See glBlendFunc or glBlendFuncSeparate for a description of the various blend factors.
In the equations that follow, source and destination
color components are referred to as
| Mode | RGB Components | Alpha Component |
|---|---|---|
GL_FUNC_ADD
|
||
GL_FUNC_SUBTRACT
|
||
GL_FUNC_REVERSE_SUBTRACT
|
||
GL_MIN
|
||
GL_MAX
|
The results of these equations are clamped to the range
The GL_MIN and GL_MAX equations are useful for applications
that analyze image data (image thresholding against a constant color,
for example).
The GL_FUNC_ADD equation is useful
for antialiasing and transparency, among other things.
Initially, both the RGB blend equation and the alpha blend equation are set to GL_FUNC_ADD.
The GL_MIN, and GL_MAX equations do not use
the source or destination factors, only the source and destination colors.
GL_INVALID_ENUM is generated if either modeRGB or modeAlpha is not one of
GL_FUNC_ADD, GL_FUNC_SUBTRACT, GL_FUNC_REVERSE_SUBTRACT,
GL_MAX, or GL_MIN.
GL_INVALID_VALUE is generated by glBlendEquationSeparatei if buf is greater
than or equal to the value of GL_MAX_DRAW_BUFFERS.
glGet with an argument of GL_BLEND_EQUATION_RGB
glGet with an argument of GL_BLEND_EQUATION_ALPHA
| OpenGL Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |
glBlendEquationSeparate
|
✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
glBlendEquationSeparatei
|
- | - | - | - | - | - | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
Copyright © 1991-2006 Silicon Graphics, Inc. Copyright © 2010-2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.