OES_draw_buffers_indexed: blendFunciOES() method
The blendFunciOES()
method of the OES_draw_buffers_indexed
WebGL extension defines which function is used when blending pixels for a particular draw buffer.
See OES_draw_buffers_indexed.blendFuncSeparateiOES()
for setting RGB and alpha components separately and WebGLRenderingContext.blendFunc()
for the WebGL 1 version of this method.
Syntax
js
blendFunciOES(buf, src, dst)
Parameters
buf
-
An integer
i
specifying the draw buffer associated with the constantgl.DRAW_BUFFERi
, see WebGL draw buffer constants. src
-
A
GLenum
specifying a multiplier for the source blending factors. Accepts the same enums as thesfactor
parameter inWebGLRenderingContext.blendFunc()
. dst
-
A
GLenum
specifying a multiplier for the destination blending factors. Accepts the same enums as thedfactor
parameter inWebGLRenderingContext.blendFunc()
.
Return value
None (undefined
).
Exceptions
- If
buf
is not a valid value, agl.INVALID_VALUE
error is thrown. - If
src
ordst
are not one of the possible values, agl.INVALID_ENUM
error is thrown. - The same blending limitations as for
WebGLRenderingContext.blendFunc()
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
You can set the blend functions for the gl.DRAW_BUFFER0
and gl.DRAW_BUFFER1
draw buffers like this:
js
const ext = gl.getExtension("OES_draw_buffers_indexed");
ext.blendFunciOES(0, gl.ONE, gl.ONE);
ext.blendFunciOES(1, gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);
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
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