Question

Given an NSMutableArray of dynamic CGPoints, what is the fastest and most efficient way to draw lines from array[0] to array[1], array[1] to array[2], etc.? Should I rewrite my function in C or C++ for better performance? Currently my framerate suffers dramatically when there are more than ~20 points in the array. I am using cocos2d v2.0.0-rc2 and I currently have:

-(void)draw
{
    for (int i = 0; i < [points count]; i+=2)
    {
        CGPoint startFromArray = [[points objectAtIndex:i] CGPointValue];
        CGPoint endFromArray = [[points objectAtIndex:i+1] CGPointValue];

        ccDrawLine(startFromArray, endFromArray);
    }

    [super draw];
}

Answer 1

There’s no need to use iteration here. Cocos2d has a built-in function called ccDrawPoly(). You can use it like this:

CGPoint *verts = malloc(sizeof(CGPoint) * [points count]);

for (int i = 0; i < [points count]; i++) {
    verts[i] = [[points objectAtIndex:i] CGPointValue];
}

ccDrawPoly(verts, [points count], NO);

free(verts);

Obviously, you’ll get even better performance if you store your CGPoints in a C array instead of boxing and unboxing them from NSValues, but if you really need the mutability, that can’t be helped.

As for the third argument of ccDrawPoly(), setting it to YES will connect the start and end points of the array, making a closed polygon, while using NO will just make a bunch of open lines.