Find midpoint between 2 game objects C#

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


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:

Code (csharp):

1. public Transform OtherObjectA; // First object of pair
2. 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

Code (csharp):

1. Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
2. 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:

Code (csharp):

1. 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.

Code (csharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class HereToMidpointOfAB : MonoBehaviour
5. {
6.     public Transform OtherObjectA; // First object of pair
7.     public Transform OtherObjectB; // Second object of pair
8.  
9.     public void Update ()
10.     {
11.         Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
12.         Vector3 directionCtoB = OtherObjectB.position - transform.position; // directionCtoB = positionB - positionC
13.         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
14.     }
15. }

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


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:

Code (csharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class HereToMidpointOfAB : MonoBehaviour
5. {
6.     public Transform OtherObjectA; // First object of pair
7.     public Transform OtherObjectB; // Second object of pair
8.  
9.     public void Update ()
10.     {
11.         Vector3 directionCtoA = OtherObjectA.position - transform.position; // directionCtoA = positionA - positionC
12.         Vector3 directionCtoB = OtherObjectB.position - transform.position; // directionCtoB = positionB - positionC
13.         Vector3 directionAtoB = OtherObjectB.position - OtherObjectA.position; // directionAtoB = target.position - source.position
14.         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
15.         Debug.DrawRay(OtherObjectA.position,  directionAtoB, Color.red); // line between A and B
16.         Debug.DrawRay(transform.position,  directionCtoA, Color.green); // line between C and A
17.         Debug.DrawRay(transform.position,  directionCtoB, Color.green); // line between C and B
18.         Debug.DrawRay(transform.position,  midpointAtoB, Color.blue); // line midway between C and B
19.     }
20. }

And here is the full project, just open the blank scene and move the objects about.
View attachment $MidpointBetween2Objects.unitypackage

Any questions just ask.

 

well done. Excellent written tutorial.

Best,

jon

 

Or to save some calculations you could just do :

Code (csharp):

1. Vector3 midPoint = (OtherObjectA.position + OtherObjectB.position) * 0.5f;

 

Thanks SubZeroGaming

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

Code (csharp):

1. 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.

 

You could always lerp it:

Code (CSharp):

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