I have high number of variables (30 uniforms (mostly vec4), about 20 variables (vec3, float, vec4) within shader) within fragment shader. It runs just fine on iPhone5S, but I have serious problem on iPhone4. GPU time is 1s / frame and 98% of the time is shader run time.
According to Apple API
OpenGL ES limits the number of each variable type you can use in a vertex or fragment shader. The OpenGL ES specification doesn’t require implementations to provide a software fallback when these limits are exceeded; instead, the shader simply fails to compile or link. When developing your app you must ensure that no errors occur during shader compilation, as shown in Listing 10-1.
But from this I quite dont understand. Do they provide SW fallback or not? Because I have no errors during compilation or linking of shader and yet performance is poor. I have comment almost everything out and just leave 2 texture lookups and directional light computation. I changed other functions to return just vec4(0,0,0,0).
Edited by Martin Perry, 07 May 2014 - 05:52 AM.