Calculate The object angle(face) having two points?

Question

C++, I want calculate the angle of the direction of the two points.

Here is a picture which shows the two points and the direction of how to get the angle of the direction?

enter image description here

p1 - start point. p2 - direction point. me need direction angle(facing?) from p1 to p2

[Πυθαγόρας](https://en.wikipedia.org/?title=Pythagorean_theorem#Pythagorean_trigonometric_identity)? — πάντα ῥεῖ, Jun 17 '15 at 17:37
Well, so what?? It's still veeery basic geometrical math, you have all the necessary functions at hand in c++ ([`#include `](http://en.cppreference.com/w/cpp/header/cmath)), and my link explains well, what to do. (You should note the c++ functions use radian angle values as arguments, rather than degrees). — πάντα ῥεῖ, Jun 17 '15 at 17:48
p1 - start point. p2 - direction point. me need direction angle from p1 to p2 — Zero Memory, Jun 17 '15 at 17:50
Please show the code you actuallly have tried, and clearly state why it fails. — πάντα ῥεῖ, Jun 17 '15 at 17:50
πάντα ῥεῖ, I tried to use: http://stackoverflow.com/posts/30898572/edit but the code returns the 0-2, but I need from 0 to 360. — Zero Memory, Jun 17 '15 at 17:53
How to convert it into direction(from start point to end point)? (0-360) ? — Zero Memory, Jun 17 '15 at 18:13
I just told you radian value [2 * π equivalents to 360° in degree](https://en.wikipedia.org/wiki/Radian#Conversion_between_radians_and_degrees)s, what's actually so hard about converting the one into the other and back? Do yourself a favor and buy a college primer math book dude. — πάντα ῥεῖ, Jun 17 '15 at 18:24

score 2 · Accepted Answer · answered Jun 17 '15 at 17:37

2

#include <cmath>

// ...
double angle = atan2(p2.y - p1.y, p2.x - p1.x);
// ...

If you want to, you can also make sure that p1 != p2, because if it is then you'll get a domain error.

answered Jun 17 '15 at 17:37

Jashaszun

http://i.imgur.com/2GX0MUw.png ?? – Zero Memory Jun 17 '15 at 17:42
1

@ZeroMemory In your image, that angle is always 90 degrees. That's the definition of a right angle. – Jashaszun Jun 17 '15 at 17:45
Your function does not return 0-360. – Zero Memory Jun 17 '15 at 17:48
StartXY: -4080.929199 , -5206.329102 . NextXY: -4029.881348 , -5174.799805 . EndXY: -1141.065918 , -4052.538818 . Angle12: 0.553291 – Zero Memory Jun 17 '15 at 17:49
p1 - start point. p2 - direction point. me need direction angle from p1 to p2 – Zero Memory Jun 17 '15 at 17:49
How to convert into angle? (0-360) ? – Zero Memory Jun 17 '15 at 17:56
@ZeroMemory [_"How to convert into angle? (0-360) ?"_](http://stackoverflow.com/questions/30898515/calculate-the-object-angleface-having-two-points#comment49837839_30898515) – πάντα ῥεῖ Jun 17 '15 at 23:04

1 Answers1