'\" t
.\" Title: glBlendEquationSeparate
.\" Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.76.1
.\" Date: 03/08/2011
.\" Manual: OpenGL 3.3
.\" Source: OpenGL 3.3
.\" Language: English
.\"
.TH "GLBLENDEQUATIONSEPAR" "3G" "03/08/2011" "OpenGL 3.3" "OpenGL 3\&.3"
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.SH "NAME"
glBlendEquationSeparate \- set the RGB blend equation and the alpha blend equation separately
.SH "C SPECIFICATION"
.HP \w'void\ glBlendEquationSeparate('u
.BI "void glBlendEquationSeparate(GLenum\ " "modeRGB" ", GLenum\ " "modeAlpha" ");"
.SH "PARAMETERS"
.PP
\fImodeRGB\fR
.RS 4
specifies the RGB blend equation, how the red, green, and blue components of the source and destination colors are combined\&. It must be
\fBGL_FUNC_ADD\fR,
\fBGL_FUNC_SUBTRACT\fR,
\fBGL_FUNC_REVERSE_SUBTRACT\fR,
\fBGL_MIN\fR,
\fBGL_MAX\fR\&.
.RE
.PP
\fImodeAlpha\fR
.RS 4
specifies the alpha blend equation, how the alpha component of the source and destination colors are combined\&. It must be
\fBGL_FUNC_ADD\fR,
\fBGL_FUNC_SUBTRACT\fR,
\fBGL_FUNC_REVERSE_SUBTRACT\fR,
\fBGL_MIN\fR,
\fBGL_MAX\fR\&.
.RE
.SH "DESCRIPTION"
.PP
The blend equations determines how a new pixel (the \*(Aq\*(Aqsource\*(Aq\*(Aq color) is combined with a pixel already in the framebuffer (the \*(Aq\*(Aqdestination\*(Aq\*(Aq color)\&. This function specifies one blend equation for the RGB\-color components and one blend equation for the alpha component\&.
.PP
The blend equations use the source and destination blend factors specified by either
\fBglBlendFunc\fR()
or
\fBglBlendFuncSeparate\fR()\&. See
\fBglBlendFunc\fR()
or
\fBglBlendFuncSeparate\fR()
for a description of the various blend factors\&.
.PP
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\&.
.TS
allbox tab(:);
lB lB lB.
T{
\fB
Mode
\fR
T}:T{
\fB
RGB Components
\fR
T}:T{
\fB
Alpha Component
\fR
T}
.T&
l l l
l l l
l l l
l l l
l l l.
T{
\fBGL_FUNC_ADD\fR
T}:T{
Rr
=
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
T}:T{
Ar
=
A
s
s
A
+
A
d
d
A
T}
T{
\fBGL_FUNC_SUBTRACT\fR
T}:T{
Rr
=
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
T}:T{
Ar
=
A
s
s
A
\-
A
d
d
A
T}
T{
\fBGL_FUNC_REVERSE_SUBTRACT\fR
T}:T{
Rr
=
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
T}:T{
Ar
=
A
d
d
A
\-
A
s
s
A
T}
T{
\fBGL_MIN\fR
T}:T{
Rr
=
min
R
s
R
d
Gr
=
min
G
s
G
d
Br
=
min
B
s
B
d
T}:T{
Ar
=
min
A
s
A
d
T}
T{
\fBGL_MAX\fR
T}:T{
Rr
=
max
R
s
R
d
Gr
=
max
G
s
G
d
Br
=
max
B
s
B
d
T}:T{
Ar
=
max
A
s
A
d
T}
.TE
.sp 1
.PP
The results of these equations are clamped to the range
0 1\&.
.PP
The
\fBGL_MIN\fR
and
\fBGL_MAX\fR
equations are useful for applications that analyze image data (image thresholding against a constant color, for example)\&. The
\fBGL_FUNC_ADD\fR
equation is useful for antialiasing and transparency, among other things\&.
.PP
Initially, both the RGB blend equation and the alpha blend equation are set to
\fBGL_FUNC_ADD\fR\&.
.PP
.SH "NOTES"
.PP
The
\fBGL_MIN\fR, and
\fBGL_MAX\fR
equations do not use the source or destination factors, only the source and destination colors\&.
.SH "ERRORS"
.PP
\fBGL_INVALID_ENUM\fR
is generated if either
\fImodeRGB\fR
or
\fImodeAlpha\fR
is not one of
\fBGL_FUNC_ADD\fR,
\fBGL_FUNC_SUBTRACT\fR,
\fBGL_FUNC_REVERSE_SUBTRACT\fR,
\fBGL_MAX\fR, or
\fBGL_MIN\fR\&.
.SH "ASSOCIATED GETS"
.PP
\fBglGet\fR()
with an argument of
\fBGL_BLEND_EQUATION_RGB\fR
.PP
\fBglGet\fR()
with an argument of
\fBGL_BLEND_EQUATION_ALPHA\fR
.SH "SEE ALSO"
.PP
\fBglGetString\fR(),
\fBglBlendColor\fR(),
\fBglBlendFunc\fR(),
\fBglBlendFuncSeparate\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
2006 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\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.