Question

Has anyone had much success on Android with creating blurred textures using blending to blur a texture?

I’m thinking of the technique described here but the crux is to take a loaded texture and then apply a blur to it so that the bound texture itself is blurred.

Answer 1

“Inplace blurring” is something a CPU can do, but using a GPU, which generally does things in parallel, you must have another image buffer as render target.

Even with new shaders, reads and writes from/to the same buffer can lead to corruption because they can be done reordered. A similar issue is, that a gaussian blurring kernel, which can handle blurring in one pass, depends on neighbor fragments which could have been modified by the kernel applied at their fragment coordinate.

If you don’t have the ‘framebuffer_object’ extension available for rendering into renderbuffers or even textures (additionally requires ‘render_texture’ extension),
you have to render into the back buffer as in the example and then do glReadPixels() to get the image back for uploading it to the source texture, or do a fast and direct glCopyTexImage2D() (OpenGL* 1.1 have this).

If the render target is too small, you can render multiple tiles.