Use multiple texture when rendering cause low framerate - iphone

Question

I tried use different to render the ground of a game. First, I create some texture and upload to GPU.
void initialize(float width,float height)
{
for(int i = 0;i < 10;i++)
{
glActiveTexture(GL_TEXTURE1 + i);
GLuint gridTexture;
glGenTextures(1, &gridTexture);
glBindTexture(GL_TEXTURE_2D, gridTexture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
setPngTexture(gameMap->texture);
glGenerateMipmap(GL_TEXTURE_2D);
}
}
Then I use the textures when render in every frame.
void render() const
{
for(int i = 0; i < map -> maps.size();i++)
{
glUniform1i(uniforms.Sampler,i);
glBindBuffer(GL_ARRAY_BUFFER, gameMap -> verticesbuffer);
glVertexAttribPointer(position, 3, GL_FLOAT, GL_FALSE, stride, 0);
glVertexAttribPointer(normal, 3, GL_FLOAT, GL_FALSE, stride, offset);
glVertexAttribPointer(texture, 2, GL_FLOAT, GL_FALSE, stride, texCoordOffset);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, gameMap -> indicesbuffer);
glDrawElements(GL_TRIANGLES, gameMap -> indexCount, GL_UNSIGNED_SHORT, 0);
}
}
The code work properly on iPhone simulator, but when I testing the app on device, it gives me a very low framerate : 2fps. If I change the line glUniform1i(uniforms.Sampler,i); to glUniform1i(uniforms.Sampler,0); the app work fine!
I'm a freshman on OpenGL ES and I'm not sure I use multiple texture in a correct way. Who can kindly tell me what's the reason of this problem and how can I correct it? Thanks a lot!

Answer 1

there are many things that could be wrong with this. You don't provide enough code to really diagnose the issue (shader source). I'd start with moving the glUniform1i(uniforms.Sampler,i); outside of your loop. It makes no sense the way your are currently using it (basically you're trying to bind uniforms.Sampler to the nth value inside your shader for map.size(). I'm pretty sure this is throwing tons of OpenGL errors. Re-read the documentation on glUniform1i