Pro OpenGL ES for iOS

84 CHAPTER 3: Building a 3D World^

You should now recognize many of the elements from the cube examples.

„ First, in line 1, tell the system that we want to work with the

GL_MODELVIEW matrix (the one that supports the transformation

information).

„ Lines 2 and 3 are identical to the ones used previously to cull out the

back of the sphere that we cannot see.

„ Lines 4 and 5 are again familiar and tell OpenGL to accept both vertex

and color information.

„ Next we supply the vertex data in line 6 and the color data in line 7.

„ Line 8 does the heavy lifting in drawing the arrays, both color and

vertices.

Now that the planet object is complete enough for this example, let’s do the driver. First,

create a new Objective-C object and call it something like

OpenGLSolarSystemController. Now add the code from Listing 3-8a and 3-8b to

initialize the object and universe.

Listing 3-8a. Initializing your universe: the header

#import <Foundation/Foundation.h>

#import <GLKit/GLKit.h>

#import "Planet.h"

@interface OpenGLSolarSystemController : NSObject

{

Planet *m_Earth;

}

-(void)execute;

-(id)init;

-(void)initGeometry;

@end

Listing 3-8b. Initializing your universe: the rest of the stuff

-(id)init

{

[self initGeometry];

return self;

}

-(void)initGeometry

{

m_Earth=[[Planet alloc] init:10 slices:10 radius:1.0 squash:1.0];

}

The earth model here is initialized at fairly low resolution: 10 stacks high, 10 slices

around.