OES_draw_buffers_indexed: blendFuncSeparateiOES() method
The blendFuncSeparateiOES()
method of the OES_draw_buffers_indexed
WebGL extension defines which function is used when blending pixels for RGB and alpha components separately for a particular draw buffer.
See OES_draw_buffers_indexed.blendFunciOES()
for setting RGB and alpha together and WebGLRenderingContext.blendFuncSeparate()
for the WebGL 1 version of this method.
Syntax
js
blendFuncSeparateiOES(buf, srcRGB, dstRGB, srcAlpha, dstAlpha)
Parameters
buf
-
An integer
i
specifying the draw buffer associated with the constantgl.DRAW_BUFFERi
, see WebGL draw buffer constants. srcRGB
-
A
GLenum
specifying a multiplier for the red, green and blue (RGB) source blending factors. Accepts the same enums as thesrcRGB
parameter inWebGLRenderingContext.blendFuncSeparate()
. dstRGB
-
A
GLenum
specifying a multiplier for the red, green and blue (RGB) destination blending factors. Accepts the same enums as thedstRGB
parameter inWebGLRenderingContext.blendFuncSeparate()
. srcAlpha
-
A
GLenum
specifying a multiplier for the alpha source blending factor. Accepts the same enums as thesrcAlpha
parameter inWebGLRenderingContext.blendFuncSeparate()
. dstAlpha
-
A
GLenum
specifying a multiplier for the alpha destination blending factor. Accepts the same enums as thesrcAlpha
parameter inWebGLRenderingContext.blendFuncSeparate()
.
Return value
None (undefined
).
Exceptions
- If
buf
is not a valid value, agl.INVALID_VALUE
error is thrown. - If
srcRGB
,dstRGB
,srcAlpha
ordstAlpha
are not one of the possible values, agl.INVALID_ENUM
error is thrown. - The same blending limitations as for
WebGLRenderingContext.blendFuncSeparate()
apply: If a constant color and a constant alpha value are used together as source and destination factors, agl.INVALID_ENUM
error is thrown.
Examples
Setting and getting blend functions
The following sets the blend functions for the draw buffers gl.DRAW_BUFFER0
(call where buf
is 0) and gl.DRAW_BUFFER1
(call where buf
is 1).
js
const ext = gl.getExtension("OES_draw_buffers_indexed");
ext.blendFuncSeparateiOES(0, gl.ONE, gl.ONE, gl.ZERO, gl.ZERO);
ext.blendFuncSeparateiOES(
1,
gl.SRC_ALPHA,
gl.ONE_MINUS_SRC_ALPHA,
gl.ZERO,
gl.ZERO
);
To get the blend functions for the gl.DRAW_BUFFER0
and gl.DRAW_BUFFER1
draw buffers, query the BLEND_SRC_RGB
, BLEND_SRC_ALPHA
, BLEND_DST_RGB
, and BLEND_DST_ALPHA
constants using WebGL2RenderingContext.getIndexedParameter()
:
js
// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_SRC_RGB, 0);
gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 0);
gl.getIndexedParameter(gl.BLEND_DST_RGB, 0);
gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 0);
// For gl.DRAW_BUFFER0
gl.getIndexedParameter(gl.BLEND_SRC_RGB, 1);
gl.getIndexedParameter(gl.BLEND_SRC_ALPHA, 1);
gl.getIndexedParameter(gl.BLEND_DST_RGB, 1);
gl.getIndexedParameter(gl.BLEND_DST_ALPHA, 1);
Specifications
Specification |
---|
WebGL OES_draw_buffers_indexed Extension Specification |
Browser compatibility
BCD tables only load in the browser