I would like to achieve FSAA on my OpenGL ES app on the iPhone.
Currently I do this by rendering the scene to a texture that is twice the width and height of the screen. I then use the nice function:
void glDrawTexiOES(GLint x, GLint y, GLint z, GLint width, GLint height);
to draw the image resized to the screen resolution.
Is there a better way to do this?
Update Bounty Added I was wondering, given that its now Jan 2010, whether there is a better way to do this on v3.1 3GS phones, etc.
For Gran Turismo on the PSP, the developers achieved an effect similar to anti-aliasing by moving the image back and forth one pixel per frame (demonstration can be found here: http://www.gtplanet.net/why-gran-turismo-psp-looks-so-good/) so if the iPhone doesn't support what you're looking for that's an option.
As of iOS 4.0, full-screen anti-aliasing is directly supported via an Apple extension to OpenGL. The basic concept is similar to what you are already doing: render the scene onto a larger framebuffer, then copy that down to a screen-sized framebuffer, then copy that buffer to the screen. The difference is, instead of creating a texture and rendering it onto a quad, the copy/sample operation is performed by a single function call (specifically, glResolveMultisampleFramebufferAPPLE()).
For details on how to set up the buffers and modify your drawing code, you can read a tutorial on the Gando Games blog which is written for OpenGL ES 1.1; there is also a note on Apple's Developer Forums explaining the same thing.
Thanks to Bersaelor for pointing this out in another SO question.
Technically iPhone's GPU (PowerVR MBX Lite) should support anti-aliasing. However, it seems that current Apple's OpenGL ES drivers (as of Jan 2009) don't expose this capability. So doing "manual AA" just like you do is pretty much the only way.
iPhone OS 3.0 + OpenGL ES 2.0. Is anyone seeing better anti-aliasing?
Sounds like you can't do it in hardware since you don't render to the framebuffer, only a texture that the iPhone composites for you.
