Blurring part of the screen - optimisation

Question

I develop 3d menu and sometimes I need to blur only part of the screen. I use a forward rendering. I create a frame buffer object with 3 color attachments. Rendering looks like this:

• bind fbo
• render objects which are blurred to the first texture
• bind the first texture
• perform vertical blur and save a result in the second texture
• bind the second texture
• perform horizontal blur and save a result in the third texture
• unbind fbo (render to the default fbo)
• bind the thrid texture
• render the third texture
• render objects which are not blurred

I can use subroutines to reduce overhead during switching shaders. I also found the following article . Do you have any other ideas how to optimize above rendering ?

Answer 1

That is the standard way of doing a Gaussian blur however, you can use only 2 textures like this:

• bind the original texture
• blur horizontally to the second texture
• bind the blurred horizontally texture
• blur vertically to the original texture