Whats the source code of LookAt from Transform.cs

Questions & Answers
1

Hello,

i’d like to know the source code of LookAt function. I try make it in c++, but its work wrong.

2

It’s not public. However, you can take a look at the CreateLookAt function of the .NET Framework, which implements a similar functionality: Matrix4x4 .NET Reference source (line 1050).

3

Yes thank you. I found a similar function, even implemented it. Only I do not fully understand how to apply the result of this function. I tried this: translated rotation.eulerAngles into Vector4 homogeneousRotation = new Vector4(eulerAngles.x, eulerAngles.y, eulerAngles.z, 1); multiplied the resulting Matrix4x4 by Vector4 and from this I set the eulerAngles of the object. But this does not give the desired result.

private void HandleObj(Transform obj, Vector3 target)
    {
        if (obj != null)
        {
            // wrist.LookAt(target);
            // return;

            Matrix4x4 rotationMatrix = LookAt2(transform.position, target, Vector3.up);

            var eulerAngles = obj.rotation.eulerAngles;
            Vector4 homogeneousRotation = new Vector4(eulerAngles.x, eulerAngles.y, eulerAngles.z, 1);

            var newAngel = MultiplyMatrixWithVector4(rotationMatrix, homogeneousRotation);
            obj.transform.eulerAngles = new Vector3(newAngel.x, newAngel.y, newAngel.z);
        }
    }

    public static Matrix4x4 LookAt2(Vector3 eye, Vector3 target,  Vector3 up)
    {
        Vector3 zaxis = Vector3.Normalize(eye - target);
        Vector3 xaxis = Vector3.Normalize(Vector3.Cross(up, zaxis));
        Vector3 yaxis = Vector3.Cross(zaxis, xaxis);

        Matrix4x4 result = Matrix4x4.zero;
        result.m00 = xaxis.x;
        result.m01 = yaxis.x;
        result.m02 = zaxis.x;
        result.m03 = 0.0f;
        result.m10 = xaxis.y;
        result.m11 = yaxis.y;
        result.m12 = zaxis.y;
        result.m13 = 0.0f;
        result.m20 = xaxis.z;
        result.m21 = yaxis.z;
        result.m22 = zaxis.z;
        result.m23 = 0.0f;
        result.m30 = -Vector3.Dot(xaxis, eye);
        result.m31 = -Vector3.Dot(yaxis, eye);
        result.m32 = -Vector3.Dot(zaxis, eye);
        result.m33 = 1.0f;
        return result;
    }

    public static Vector4 MultiplyMatrixWithVector4(Matrix4x4 matrix, Vector4 vector)
    {
        //matrix row * vector column

        var i0 = (matrix[0, 0] * vector.x + matrix[0, 1] * vector.y + matrix[0, 2] * vector.z +
                  matrix[0, 3] * vector.w);
        var i1 = (matrix[1, 0] * vector.x + matrix[1, 1] * vector.y + matrix[1, 2] * vector.z +
                  matrix[1, 3] * vector.w);
        
        var i2 = (matrix[2, 0] * vector.x + matrix[2, 1] * vector.y + matrix[2, 2] * vector.z +
                  matrix[2, 3] * vector.w);
        
        var i3 = (matrix[3, 0] * vector.x + matrix[3, 1] * vector.y + matrix[3, 2] * vector.z +
                  matrix[3, 3] * vector.w);

        return new Vector4(i0, i1, i2, i3);
    }

Tell me, please, how to properly apply the resulting Matrix4x4?
@BastianUrbach