How to get the angle to an object from angle you are facing

Question

I am making an creature simulator where the creatures have a neural net for a brain.

One of the inputs to the net is the angle it has to travel to go to be facing the nearest piece of food. I can get the nearest piece of food, but I need a way of getting the angle it needs to travel to be facing the piece of food.

For example, if it was facing the food, it would be zero, and if it was facing away it would be 180. I got the creatures angle, if it is facing up it would be 0 degrees, and if its facing right its 90 degrees.

Sounds like a near duplicate of How can I calculate the angle between two 2D vectors? or Comparing angles and working out the difference. — Nathan Reed, Aug 02 '13 at 21:40
The programming is easy; this is a vector algebra problem. Any vector algebra reference will tell you how to determine the angle between two vectors in either 2- or 3-dimensions. — Pieter Geerkens, Aug 02 '13 at 21:42
Yeah but I need something in python because that's the only language I know — Justin6533, Aug 02 '13 at 22:29
The other questions are not language specific. What, specifically, are you having trouble understanding from the other questions? — House, Aug 02 '13 at 22:47
Aside from being flagged for duplicate questions, you'll get into more interesting math questions down the road. Having one of these can go a long way: http://www.amazon.com/Mathematics-Programming-Computer-Graphics-Edition/dp/1435458869 or http://www.amazon.com/Essential-Mathematics-Games-Interactive-Applications/dp/0123742978 — Jovan, Aug 03 '13 at 01:49
possible duplicate of Finding vectors with two points or How can I calculate the angle between two 2d vectors — Pip, Aug 03 '13 at 03:07

score 0 · Answer 1 · answered Aug 04 '13 at 18:56

look up dot product on wikipedia. You need to calculate the dot product of the normalized direction vector you are facing and the normal vector of the surface. something like x1*x2+y1*y2. To get the angle between the two vectors you have to use the acos function.

How to get the angle to an object from angle you are facing

1 Answers1