Dynamic allocate array of struct for Open GL in Objective-C

Question

I'm beginner in Open GL but I already can draw simple triangle, rectangle etc.

My problem is:

I have the structure and static array of that structure

typedef struct {
    GLKVector3 Position;
} Vertex;

const Vertex Vertices[] = {
    {{0.0, 0.0, 0.0}},
    {{0.5, 0.0, 0.0}},
    {{0.5, 0.5, 0.0}},
    {{0.0, 0.5, 0.0}},
    {{0.0, 0.0, 0.0}}
};

...some code

but I need array of vertices create dynamically... :(

Example:

typedef struct {
    GLKVector3 Position;
} Vertex;

  instance variable - iVertices of type Vertex

- (void) viewDidLoad {
   int numOfVertices = 0;
   Vertex vertices[] = {{0.0, 0.0, 0.0}};
   [self addVertex:vertices atIndex:numOfVertices];
   numOfVertices ++;
   Vertex vertices[] = {{0.5, 0.0, 0.0}};
   [self addVertex:vertices atIndex:numOfVertices];
   numOfVertices ++;
   Vertex vertices[] = {{0.5, 0.5, 0.0}};
   [self addVertex:vertices atIndex:numOfVertices];
}

- (void) addVertex:(Vertex) vertex atIndex:(int) num {
   iVertices[num] = vertex;
}

...and somewhere
glBufferData(GL_ARRAY_BUFFER,
             sizeof(iVertices),
             iVertices,
             GL_STATIC_DRAW);

and this is not allowed in Objective-C or I don't know how to do it :(

malloc nor callow doesn't help to me...

Thanks a lot!

Answer 1

Your main problem here is that you can't just take the sizeof an array that is an instance variable because it's a pointer which will return a size of 8. Instead you're going to have to save the count of the array somewhere else as another instance variable (or use numOfVertices) and multiply it by the sizeof(int). So something like glBufferData(GL_ARRAY_BUFFER, numOfVariable*sizeof(int), iVertices, GL_STATIC_DRAW); should work for your case.