Getting point between two vectors help math experts!

Unity Engine
1

In a Vector3 world, I have point A and point B, and all I want to do is get point C as you can see in this image, I know it’s possible but may require advanced math techniques that I don’t have, The only reason I want to do this is because I want to rotate a gameobject in pont A in the direction of point B but only in his local Y axis, thanks guys!

This is the code I’m using to rotate game object in pont A in the direction of point B:

pointA.rotation = Quaternion.Slerp(
pointA.rotation,
Quaternion.LookRotation((pointB - pointA).normalized),
Time.deltaTime
);

2

Im not 100% sure, but I think you might be looking for cross…

1 Like
3

@JamesLeeNZ Yup if you want to get point C in world space like the diagram states, you should use Cross like James has listed.

4

Maybe the ClosestPointsOnTwoLines method found here can help.
http://wiki.unity3d.com/index.php/3d_Math_functions

Ill paste it here in case the link dies
Click for code

    public static bool ClosestPointsOnTwoLines(out Vector3 closestPointLine1, out Vector3 closestPointLine2, Vector3 linePoint1, Vector3 lineVec1, Vector3 linePoint2, Vector3 lineVec2){
        closestPointLine1 = Vector3.zero;
        closestPointLine2 = Vector3.zero;
        float a = Vector3.Dot(lineVec1, lineVec1);
        float b = Vector3.Dot(lineVec1, lineVec2);
        float e = Vector3.Dot(lineVec2, lineVec2);
        float d = a*e - b*b;
        //lines are not parallel
        if(d != 0.0f){
            Vector3 r = linePoint1 - linePoint2;
            float c = Vector3.Dot(lineVec1, r);
            float f = Vector3.Dot(lineVec2, r);
            float s = (b*f - c*e) / d;
            float t = (a*f - c*b) / d;
            closestPointLine1 = linePoint1 + lineVec1 * s;
            closestPointLine2 = linePoint2 + lineVec2 * t;
            return true;
        }
        else{
            return false;
        }
    }

You may want to edit that code to instead of returning bool and using out, to just return what you want.

5

The cross product returns a vector that is perpendicular to both the vectors passed in. Not sure this will help you.

I’m struggling to see how A, B and C are related to each other…

6

–Eric