The colorMaskiOES() method of the OES_draw_buffers_indexed WebGL extension sets which color components to enable or to disable when drawing or rendering for a particular draw buffer. It's the indexed version of WebGL 1's WebGLRenderingContext.colorMask() method.

buf

An integer i specifying the draw buffer associated with the constant gl.DRAW_BUFFERi, see WebGL draw buffer constants.

r

A GLboolean specifying whether or not the red color component should be written into the draw buffer.

g

A GLboolean specifying whether or not the green color component should be written into the draw buffer.

b

A GLboolean specifying whether or not the blue color component should be written into the draw buffer.

a

A GLboolean specifying whether or not the red alpha (transparency) component should be written into the draw buffer.

None (undefined).

• If buf, r, b, g, or a are not a valid values, a gl.INVALID_VALUE error is thrown.

You can set the color masks for the gl.DRAW_BUFFER0 and gl.DRAW_BUFFER1 draw buffers like this:

const ext = gl.getExtension("OES_draw_buffers_indexed");

ext.colorMaskiOES(0, 1, 0, 0, 0);
ext.colorMaskiOES(1, 0, 1, 0, 0);

To get the color masks for the gl.DRAW_BUFFER0 and gl.DRAW_BUFFER1 draw buffers, query the COLOR_WRITEMASK constant using WebGL2RenderingContext.getIndexedParameter():

gl.getIndexedParameter(gl.COLOR_WRITEMASK, 0);
gl.getIndexedParameter(gl.COLOR_WRITEMASK, 1);

• WebGL2RenderingContext.getIndexedParameter()
• WebGLRenderingContext.colorMask()