Question

I am porting an Android app I made to iPhone and running into problems with the syntax (I think)

I’m basing the project off of the example from
http://iphonedevelopment.blogspot.com/2009/04/opengl-es-from-ground-up-part-2-look-at.html

I would like to pull out the geometry from the rendering process to keep the code modular but I can’t seem to get it to work. I’ve created a class called Icosahedron (comments are my understanding of what’s going on)
Icosahedron.h

#import <Foundation/Foundation.h>
#import "OpenGLCommon.h"



@interface Icosahedron : NSObject {
 Vertex3D *vertices[12]; //allocate a group of 12 Vertex3D pointers
 Vertex3D *normals[12]; // ditto
 GLubyte *faces[60]; // ditto but with 60 face values
}

// Declare methods
-(Vertex3D *) vertices; 
-(void) setVertices:(Vector3D *)setVerts; 

-(Vertex3D *) normals;
-(void) setNormals:(Vector3D *)setNorms;

-(GLubyte *) faces;
-(void) setFaces:(GLubyte *)setFaces;

@end

Icosahedron.m

#import "Icosahedron.h"


@implementation Icosahedron

// Returns the pointer to the vertices instance variable
-(Vector3D *) vertices{
 return *vertices;
}

-(void) setVertices:(Vector3D *)setVerts
{
 //vertices=setVerts[0];
}

-(Vector3D *) normals{
 return *normals;
}

-(void) setNormals:(Vector3D *)setNorms
{
 //normals=setNorms;
}

-(GLubyte *) faces{
 return *faces;
}

-(void) setFaces:(GLubyte *)setFaces
{
 //faces=setFaces;
}
/**/
-(id)init
{
 // super method
 self=[super init];

    // create 12 Vector3D objects and populate them...
 Vector3D tempVert[12]={
        {0, -0.525731, 0.850651},             // vertices[0]
        {0.850651, 0, 0.525731},              // vertices[1]
        {0.850651, 0, -0.525731},             // vertices[2]
        {-0.850651, 0, -0.525731},            // vertices[3]
        {-0.850651, 0, 0.525731},             // vertices[4]
        {-0.525731, 0.850651, 0},             // vertices[5]
        {0.525731, 0.850651, 0},              // vertices[6]
        {0.525731, -0.850651, 0},             // vertices[7]
        {-0.525731, -0.850651, 0},            // vertices[8]
        {0, -0.525731, -0.850651},            // vertices[9]
        {0, 0.525731, -0.850651},             // vertices[10]
        {0, 0.525731, 0.850651}               // vertices[11]
    };
    // same...
 Vector3D tempNorm[12]={
        {0.000000, -0.417775, 0.675974},
        {0.675973, 0.000000, 0.417775},
        {0.675973, -0.000000, -0.417775},
        {-0.675973, 0.000000, -0.417775},
        {-0.675973, -0.000000, 0.417775},
        {-0.417775, 0.675974, 0.000000},
        {0.417775, 0.675973, -0.000000},
        {0.417775, -0.675974, 0.000000},
        {-0.417775, -0.675974, 0.000000},
        {0.000000, -0.417775, -0.675973},
        {0.000000, 0.417775, -0.675974},
        {0.000000, 0.417775, 0.675973},
    };


 // face values
 GLubyte tempFaces[60]={
        1, 2, 6,
        1, 7, 2,
        3, 4, 5,
        4, 3, 8,
        6, 5, 11,
        5, 6, 10,
        9, 10, 2,
        10, 9, 3,
        7, 8, 9,
        8, 7, 0,
        11, 0, 1,
        0, 11, 4,
        6, 2, 10,
        1, 6, 11,
        3, 5, 10,
        5, 4, 11,
        2, 7, 9,
        7, 1, 0,
        3, 9, 8,
        4, 8, 0,
    };

   // set the instance pointers to the temp values
 *vertices=tempVert;
 *normals=tempNorm;
 *faces=tempFaces;

at this point the values are NOT properly populated, only the first value is correct.

 return self;

}

@end

All I want to do is to be able to call something like

...
ico=[[Icosahedron alloc] init];
glVertexPointer(3, GL_FLOAT, 0, [ico vertices]);
...

in the rendering section but it the farthest I’ve been able to get is setting the first value of the Vertex3Ds inside the Icosahedron class and I get ‘out of scope’ in the debugger for any of the Icosahedron’s values in the rendering class.

I suspect that this is just me learning Objective-C’s quirks but I’ve tried many different approaches for a few days and nothing seems to get me anywhere.

Please help me Overflow-Wan, you’re my only hope.

Answer 1

You’re getting your pointers and arrays mixed up. You’d want something like this:

Vertex3D vertices[12];

- (void) setVertices: (Vertex3D *)newVertices;
{
    memcpy( vertices, newVertices, 12 * sizeof( Vertex3D ) );
}

- (Vertex3D *) vertices;
{
    return vertices;
}

To copy arrays in C you have to use memcpy (or a hand-written loop), you cannot do this with the assignment operator.