Why the starting project "OpenGL Game" in Xcode has 2 cubes? - ios

Question

I am new in iOS OpenGL ES. And I created an OpenGL project "OpenGl Game" in Xcode 5. Then I build and run, there are 2 cubes rotating around. I read the code and do not understand why there is 2 cubes instead of 1?
Here is the code related to the cubes:
- (void)update{
float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height);
GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);
self.effect.transform.projectionMatrix = projectionMatrix;
GLKMatrix4 baseModelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -4.0f);
baseModelViewMatrix = GLKMatrix4Rotate(baseModelViewMatrix, _rotation, 0.0f, 1.0f, 0.0f);
// Compute the model view matrix for the object rendered with GLKit
GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.5f);
modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotation, 1.0f, 1.0f, 1.0f);
modelViewMatrix = GLKMatrix4Multiply(baseModelViewMatrix, modelViewMatrix);
self.effect.transform.modelviewMatrix = modelViewMatrix;
// Compute the model view matrix for the object rendered with ES2
modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, 1.5f);
modelViewMatrix = GLKMatrix4Rotate(modelViewMatrix, _rotation, 1.0f, 1.0f, 1.0f);
modelViewMatrix = GLKMatrix4Multiply(baseModelViewMatrix, modelViewMatrix);
_normalMatrix = GLKMatrix3InvertAndTranspose(GLKMatrix4GetMatrix3(modelViewMatrix), NULL);
_modelViewProjectionMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);
_rotation += self.timeSinceLastUpdate * 0.5f;
}
It seems that GLKit and ES2 renders a cube respectively, but I don't know why?

Answer 1

The "OpenGL Game" template creates a program that renders 2 cubes into the GLKView. One of those cubes is rendered using the GLKit analogs of the old OpenGL ES 1.1 fixed function pipeline, the other cube is rendered through an ES 2.0 pipeline using the fragment and vertex shaders included in the template.
I think they do both so you have a working starting point for whichever pipeline you choose to use. For my current ES 2.0 project I simply stripped out all of the code relating to the ES1.1 cube and built on the code provided for the 2.0 pipeline. If you were porting some existing ES 1.1 code into GLKit you might do the opposite and remove all the stuff relating to the ES 2.0 cube.