Find midpoint between 2 game objects C#

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A short tutorial on finding a midpoint between 2 objects.

You may want a player to fire a weapon that goes towards the center point of 2 other objects or you may want to instantiante and object between 2 objects…

I will use the example of drawing a line from a cube C to the center point between 2 spheres A B in 3D space.
So create a new C# script and attach it to the cube C
1479721--81849--$problem.jpg

You will need the Transform of the 2 objects you want to find the midpoint of so you can either assign these in the inspector or ‘find’ them:

public Transform OtherObjectA; // First object of pair
public Transform OtherObjectB; // Second object of pair

Now you need to create a vector from C to A and from C to B

To get the vector that points from a source to a target you subtract the source vector from the target vector:
target.position - start.position

Now in this example we need to do this 2 times, once for C to A and once for C to B

so vector C to A is A.position - C.position
and vector C to B is B.position - C.position

Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
Vector3 directionCtoB = OtherObjectB.position - transform.position; // directionCtoB = positionB - positionC

Now all you need to do is use the midpoint formula http://www.purplemath.com/modules/midpoint.htm

so in our example we use:
MidPoint = ((pointA.x + pointB.x)/2, (pointA.y + pointB.y)/2, (pointA.z + pointB.z)/2)

and to assign this to a new vector in Unity:

Vector3 midpointAtoB = new Vector3((directionCtoA.x+directionCtoB.x)/2.0f,(directionCtoA.y+directionCtoB.y)/2.0f,(directionCtoA.z+directionCtoB.z)/2.0f);

And thats it.

using UnityEngine;
using System.Collections;

public class HereToMidpointOfAB : MonoBehaviour
{
	public Transform OtherObjectA; // First object of pair
	public Transform OtherObjectB; // Second object of pair

	public void Update ()
	{
		Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
		Vector3 directionCtoB = OtherObjectB.position - transform.position; // directionCtoB = positionB - positionC
		Vector3 midpointAtoB = new Vector3((directionCtoA.x+directionCtoB.x)/2.0f,(directionCtoA.y+directionCtoB.y)/2.0f,(directionCtoA.z+directionCtoB.z)/2.0f); // midpoint between A B this is what you want
	}
}

Here is an example using the above code to draw debug rays showing all these vectors:

1479721--81857--$midpoint.jpg
1479721--81857--$midpoint.jpg853×596 40.3 KB

The 2 green lines are C to A and C to B

The red line just shows the line joining objects A and B

The blue line is the result we wanted and is the line that always points from the source to the center of the space between objects A and B

Here is the script that shows these lines:

using UnityEngine;
using System.Collections;

public class HereToMidpointOfAB : MonoBehaviour
{
	public Transform OtherObjectA; // First object of pair
	public Transform OtherObjectB; // Second object of pair

	public void Update ()
	{
		Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
		Vector3 directionCtoB = OtherObjectB.position - transform.position; // directionCtoB = positionB - positionC
		Vector3 directionAtoB = OtherObjectB.position - OtherObjectA.position; // directionAtoB = target.position - source.position 
		Vector3 midpointAtoB = new Vector3((directionCtoA.x+directionCtoB.x)/2.0f,(directionCtoA.y+directionCtoB.y)/2.0f,(directionCtoA.z+directionCtoB.z)/2.0f); // midpoint between A B
		Debug.DrawRay(OtherObjectA.position,  directionAtoB, Color.red); // line between A and B
		Debug.DrawRay(transform.position,  directionCtoA, Color.green); // line between C and A
		Debug.DrawRay(transform.position,  directionCtoB, Color.green); // line between C and B
		Debug.DrawRay(transform.position,  midpointAtoB, Color.blue); // line midway between C and B
	}
}

And here is the full project, just open the blank scene and move the objects about.
1479721–81858–$MidpointBetween2Objects.unitypackage (5.63 KB)

Any questions just ask.

1 Like
2

well done. Excellent written tutorial.

Best,

jon

3

Or to save some calculations you could just do :

Vector3 midPoint = (OtherObjectA.position + OtherObjectB.position) * 0.5f;
6 Likes
4

Thanks SubZeroGaming

MikeUpchat, I wanted to stretch it out so people could understand the maths behind it hence lines like:

Vector3 midpointAtoB = new Vector3((directionCtoA.x+directionCtoB.x)/2.0f,(directionCtoA.y+directionCtoB.y)/2.0f,(directionCtoA.z+directionCtoB.z)/2.0f);

To show how each component of the vector is constructed.

5

You could always lerp it:

Vector3 mid = Vector3.Lerp(OtherObjectA.position, OtherObjectb.position, 0.5f);
1 Like