glBlendEquation — specify the equation used for both the RGB blend equation and the Alpha blend equation
void glBlendEquation(
|
GLenum mode); |
void glBlendEquationi(
|
GLuint buf, |
GLenum mode); |
buf
for glBlendEquationi, specifies the index of the draw buffer
for which to set the blend equation.
mode
specifies how 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 determine how a new pixel (the ''source'' color)
is combined with a pixel already in the framebuffer (the ''destination''
color). This function sets both the RGB blend equation and the alpha
blend equation to a single equation. glBlendEquationi
specifies the blend equation for a single draw buffer whereas glBlendEquation
sets the blend equation for all draw buffers.
These 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 mode 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 glBlendEquationi 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 |
glBlendEquation
|
✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
glBlendEquationi
|
- | - | - | - | - | - | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
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