2D游戏，将玩家1转到玩家2

Question

I have a 2D game. Each player has its location(x,y) and heading(right is 0deg, up is 90deg etc.) I need a method, to set Player1 heading towards Player2. I tried to calculate it by calculating slope -

slope = (player2.y - player1.y)/(player2.x - player1.x)
heading = degrees(atan(slope))

However it doesn´t return correct result everytime. Would you recommend me any other approach?

Answer 1

You are suffering from the fact that atan(slope) cannot deliver correct values for all directions. This is because the slope doesn't include the direction. A turn of 180° will leave the slope unchanged. Mathematically, this derives from the fact that -y/-x = y/x.

You are not the first to find this out. A traditional solution for the situation was always to look closely at the signs of the x and y values and then decide in which quadrant the result of the atan() should be located.

Nowadays this is done in the function with the uninspired name atan2() . This receives two values (y and x) and does all that is required to find out the proper direction angle in the range (-180°, +180°], given as radians, so it is the range (-pi, +pi].