Drawing triangle/arrow on a line with CGContext

Question

I am using the framework of route-me for working with locations. In this code the path between two markers(points) will be drawn as a line.

My Question: \"What code shou

Answer 1

I found this question as I had the same. I took drawnonward's example and it was so close... But with a flipping of cos and sin, I was able to get it to work:

r = atan2( ny - my , nx - mx );
r += M_PI;
bx = nx;
by = ny;
dx = bx + cos( r ) * length;
dy = by + sin( r ) * length;
r += M_PI_2; // perpendicular to path
ax = dx + cos( r ) * width;
ay = dy + sin( r ) * width;
cx = dx - cos( r ) * width;
cy = dy - sin( r ) * width;

Once I did that, my arrows were pointed exactly the wrong way. So I added that second line (r += M_PI;)

Thanks go to drawnonward!