Question

I have an NSMutableArray called mVerticies stored as a member of my class and I’d like to place them into a float array to draw them with glVertexAttribPointer.

Normally when drawing, I would have something like:

float verticies[] = {-1, -1, 1, -1};

// ... prepare to draw

glVertexAttribPointer(GLKVertexAttribPosition,
    2, GL_FLOAT, GL_FALSE, 0, verticies);

// ... draw

But in order to use the glVertexAttribPointer function, i need a float[]. The verticies are stored as an NSMutableArray because they change quite often. Is there an easy way to either store a dynamic float[] as a member or to quickly convert an NSMutableArray to a float[]?

Answer 1

Assuming the values are stored as NSNumbers, you can do something like this:

float *floatsArray = malloc([numbersArray count] * sizeof(float));
if (floatsArray == NULL) {
    // handle error
}
[numbersArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(NSNumber *number, NSUInteger idx, BOOL *stop) {
    floatsArray[idx] = [number floatValue];
}];

// use floatsArray

free(floatsArray);