Is there anyway to use Subtract blend mode?

[rkdrnf]

I'm trying to create color overlay effects, except certain area on the screen.

My plan was to cover whole screen as ADD Blendmode with color of my choice,
and remove effect from certain area by applying SUBTRACT Blendmode with the same color used in ADD Blendmode.

But It seems there's no Subtract Blendmode in pixi v4.

Is there any workaround I can try?
or can I implement custom blend mode in pixi v4?

[englercj]

Can you not use a mask to remove the additive sprite from certain areas?

[ivanpopelyshev]

I think params for subtract are [gl.ONE, gl.ONE] , but functions are [gl.FUNC_REVERSE_SUBTRACT, gl.FUNC_ADD]

You can make custom blendmode
http://www.html5gamedevs.com/topic/31803-scratch-card-effect/?tab=comments#comment-182673

However, pixi webglstate does not change blend function:
https://github.com/pixijs/pixi.js/blob/dev/src/core/renderers/webgl/WebGLState.js#L149

Lets patch it and bring everything together: https://www.pixiplayground.com/#/edit/6c0X5xaWa2MMy6vXfIix0

TA-DA!

P.S. Really? I didnt notice that ticket for 5 days?

[ivanpopelyshev]

Though, it doesnt help with your plan, because SUBTRACT does not subtract alpha. Change second FUNC_ADD to FUNC_REVERSE_SUBTRACT and it'll work just fine.

[ivanpopelyshev]

Maybe that's for your case:
KNOCKOUT: [gl.ZERO, gl.ONE_MINUS_SRC_ALPHA, gl.ZERO, gl.ONE_MINUS_SRC_ALPHA]

[lock]

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