In this branch, I'm maintaing another approach to render camera preview on processing's GLSurfaceView. The idea is to render camera preview on a SurfaceTexture and as soon as the new frame is received, copy the data from this SurfaceTexture to a custom texure bound to target GL_TEXTURE_2D. We cannot directly render to processing's own texture because it's bound GL_TEXTURE_2D target, whereas for the preview to happen, the texture should be bound to GL_TEXTURE_EXTERNAL_OES.

Behind the hood :

I create a framebuffer object and a custom texture object, which is bound to target GL_TEXTURE_2D, and attach this texture to the previously created framebuffer at GL_COLOR_ATTACHMENT0. I then render SurfaceTexture's shader output to this framebuffer and it atomatically gets rendered upon the custom texture I created. I then follow the approach as being done in the Syphon library - https://github.com/Syphon/Processing/blob/master/Processing_2_0/src/codeanticode/syphon/SyphonClient.java#L271