discard statement

[ptmt]

It is possible to tell the fragment shader it shouldn't write any pixel. This can be done using the "discard" statement.

https://www.opengl.org/sdk/docs/tutorials/ClockworkCoders/discard.php

The desired behavior: https://www.shadertoy.com/view/XlBXRy

The same (?) code on Rnplay.org which doesn't work as expected (maybe it shouldn't?): https://rnplay.org/apps/PUJnuw

[ptmt]

Or is there any way to use previous computed fragment as a texture for next pass?

[gre]

There is nothing to do such thing yet. We currently always clear, this is why there are no accumulation of pixels.

I guess having a way to map the previous content as a texture would be a great feature as you suggested.

[gre]

Also on the RNPlay example, it's weird that it black-blinks, do you also get this in the phone?

[ptmt]

No, it's okay on the simulator and device.

Thanks for a quick answer. I will try to make a proof-of-concept pull request. I'm also working on React Native for OS X and would be super nice to get GLSL on that eventually, so learning gl-react makes a lot of sense.

[gre]

Cool :)

I'm not sure what's the simplest way to implement this, my first thoughts are:
we need some way to copy the previous drawing buffer into a framebuffer.
Maybe using glBlitFramebuffer for this? However i'm not sure we have it in the OpenGL version we are using. It also is not available in WebGL (for future gl-react impl). But one solution is to use a "copy" shader.

Now on the user side:
I think we can introduce a new type of texture: GL.DrawingBuffer which means "use the previous drawing buffer".

<GL.View ... uniforms={{ backbuffer: GL.DrawingBuffer }} />

[ptmt]

I just want to say that I was able to solve my issue with replacing shaders partially with ReactART instead.

It definetly would be much powerful to achieve that in gl-react way, hope to find time to figure out how. I also tried to not clearing buffer on the each iteration and of course the screen was blinking.

[gre]

https://github.com/ProjectSeptemberInc/gl-react/issues/25 should be able to address this via storing into a preserved framebuffer, there are some work involved and a bit more thoughts on the API / internal formats / implementations.

[gre]

I'm approaching a spec solution to solve this (and much more) see https://github.com/ProjectSeptemberInc/gl-react/issues/27#issuecomment-174298635
I'm closing this issue in favor of that one

[ptmt]

Thanks! Awesome project, one of the best in the RN world.

On Wed, 17 Feb 2016 at 16:13 Gaëtan Renaudeau notifications@github.com
wrote:

I'm approaching a spec solution to solve this (and much more) see ProjectSeptemberInc/gl-react#27
(comment)
https://github.com/ProjectSeptemberInc/gl-react/issues/27#issuecomment-174298635
I'm closing this issue in favor of that one

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