GLBLENDEQUATION - Online Linux Manual Page

Section : 3G
Updated : 01/20/2022
Source : [FIXME: source]
Note : [FIXME: manual]

NAME

glBlendEquation − specify the equation used for both the RGB blend equation and the Alpha blend equation

C SPECIFICATION

void glBlendEquation(GLenum

mode

);

void glBlendEquationi(GLuint

buf

, GLenum

mode

);

PARAMETERS

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

DESCRIPTION

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 R s G s B s A s and R d G d B d A d, respectively. The result color is referred to as R r G r B r A r. The source and destination blend factors are denoted s R s G s B s A and d R d G d B d A, respectively. For these equations all color components are understood to have values in the range 0 1.

R
s
⁢
s
R
+
R
d
⁢
d
R

Gr
G
s
⁢
s
G
+
G
d
⁢
d
G

Br
B
s
⁢
s
B
+
B
d
⁢
d
B
A
s
⁢
s
A
+
A
d
⁢
d
A
R
s
⁢
s
R
−
R
d
⁢
d
R

Gr
G
s
⁢
s
G
−
G
d
⁢
d
G

Br
B
s
⁢
s
B
−
B
d
⁢
d
B
A
s
⁢
s
A
−
A
d
⁢
d
A
R
d
⁢
d
R
−
R
s
⁢
s
R

Gr
G
d
⁢
d
G
−
G
s
⁢
s
G

Br
B
d
⁢
d
B
−
B
s
⁢
s
B
A
d
⁢
d
A
−
A
s
⁢
s
A
min
⁡

R
s

R
d

Gr
min
⁡

G
s

G
d

Br
min
⁡

B
s

B
d
min
⁡

A
s

A
d
max
⁡

R
s

R
d

Gr
max
⁡

G
s

G
d

Br
max
⁡

B
s

B
d
max
⁡

A
s

A
d

Mode	RGB Components	Alpha Component
GL_FUNC_ADD	Rr



Ar

GL_FUNC_SUBTRACT	Rr



Ar

GL_FUNC_REVERSE_SUBTRACT	Rr



Ar

GL_MIN	Rr



Ar

GL_MAX	Rr



Ar

The results of these equations are clamped to the range 0 1.

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

NOTES

The GL_MIN

, and

GL_MAX

equations do not use the source or destination factors, only the source and destination colors.

ERRORS

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

buf

is greater than or equal to the value of

GL_MAX_DRAW_BUFFERS

ASSOCIATED GETS

glGet

(

) with an argument of

GL_BLEND_EQUATION_RGB

glGet

(

) with an argument of

GL_BLEND_EQUATION_ALPHA

VERSION SUPPORT

	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	−	−	−	−	−	−	✔	✔	✔	✔	✔	✔