How to find the mid-point of two angles(Python)?

Game Engine Game Engine Support and Discussion
1

Just as the title says. I tried adding the angles and dividing by two, but that didn’t give proper results. I tried converting the angles to two-component vectors then finding the mid-point between them(by normalizing their sum), but that approach fails when the two angles are exactly opposite. Any suggestions? Thanks.

In case it’s not clear what I mean by mid-point: I mean the angle that is exactly halfway between one angle and another(and I’m talking 2D angles, not Euler angles).

2

like an angle in degrees?

adding them together and dividing by two should work fine… what’s the problem?

3

Here’s an example to show the problem: 355 degrees and 5 degrees are only 10 degrees apart from each other. The real mid-point between them would be 360 or 0 degrees. However, (355 + 5) /2 = 180, which is clearly an incorrect answer.

Blender actually uses radians instead of degrees, but the problem is the same either way.

4

I think I may have figured it out now. It involves conversion to vectors and atan2. Here’s a sample, if anyone’s interested:

import math
pi = math.pi

Angle1 = (Insert any number)
Angle2 = (Insert any number)

Vec1 = (math.sin(Angle1), math.cos(Angle1))
    
Vec2 = (math.sin(Angle2), math.cos(Angle2))
  
VecSum = tuple(sum(x) for x in zip(Vec1, Vec2))

FinalVec = VecSum
FinalVec = tuple(x/(math.sqrt(VecSum[0]**2 + VecSum[1]**2)) for x in FinalVec)

FinalAngle = math.atan2(FinalVec[0], FinalVec[1])

FinalAngle is the midpoint of Angle1 and Angle2. I’m not 100% sure it works, but it seems to so far.

5

If you work with a domain of -180 to 180 degrees it will work better. So convert 355 to -5 and then continue along you’re original path.

6

If you limit the numerator to the range 0-359 in your original equation I think it will work. To do this use the modulus operator:


mid_angle = ((angle1 + angle2)%360)/2
7

Do you need an angle or do you need a vector?

8

The mathutils.Vector type carries the angle method, which calculates the angle between two vectors.

9

Thanks for the replies, guys.

andrew_101: Hmm, that doesn’t seem like it would really solve the problem. For instance, what if the two angles were -175 and 175?

Kupoman: I just tried that out, and it still seems to have the same problem as before.

Monster: I need an angle, but I can always convert from a vector if need be.

Goran: That’s not quite what I’m looking for.

Anyway, although my previous method was working fine, I found a much simpler and more elegant method here(the wording is kind of confusing, though):

I’ll mark this thread as solved, because that’s probably the best way to do it.