koobas.hobune.stream
Angle between two lines in 2D
Hey, I've got a problem dealing with the Vector2.Angle and the Vector3.Angle The thing is during runtime I define three points A,B and C which are in 2D world.
and eventually two lines will be used , (A,B) and (B,C) I'm trying to figure out the angle between those two lines. I've tried Vector2.Angle(B-A,C-B) and bunch of others, but I think I don't understand the essential concept of the Angle() method.
The picture will illustrate my point! Click Here
how to calculate Alpha ??
Thanks for your time
So you're describing a shape like this?
It's important to note that vectors have both length and direction. The vector from A to B is not the same as the vector from B to A. They have equal length, but opposite direction.
So, this bit:
Vector2.Angle(B-A,C-B)
That's not running the comparison you might expect, because one of your vectors is pointing "backwards". You end up calculating the supplementary angle:
So, what you probably want is this:
Vector2.Angle(B-A, B-C);
Awesome man.... Thanks a lot, it did the trick
Have a good one !
The dot product between two vectors returns the cosine of the angle.
float dot = Vector2.Dot(A, B);
float angleInRadians = Mathf.Acos(dot);
float angle = Mathf.Rad2Deg(angleInRadians); //to degrees
Note: A and B need to be NORMALIZED for this to work!
Keep in mind that this will only produce angles between 0 and 180 degrees. You'll need to do some additional trickery to compensate for that. For 2d vectors this is not too hard:
Vector3 cross = Vector3.Cross(new Vector3(A.x, A.y, 0), new Vector3(B.x, B.y, 0));
cross.z will be positive if the rotation is clockwise or negative if the rotation is counter-clockwise. Or the other way around, I'm not sure :P. Either way, you'll be able to figure out what to do in case you want to detect angles larger than 180 degrees.
It's very simple with physics. Let two lines be vector a and vector b then the angle cos theta will equal to A.B(dot product)/a mode cross product to b mode.
The problem is I can't seem to struct the lines A line from A to B is for example : Vector2 AB = A+B; or Vector2 AB = A-B or something else ?!
I mean logically I know it and mathematically but to apply it in unity that's where's my pickle
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