JensKrumsieck/ChemSharp

using System.Numerics;

namespace ChemSharp.Molecules.Blazor.Extensions;

public static class MoleculeUtil
{
    /// <summary>
    ///     Calculates Bond Rotation in 3D Space and returns midpoint and quaternion
    /// </summary>
    /// <param name="bond"></param>
    /// <returns></returns>
    public static (Vector3 position, Quaternion rotation) CalculateRotation(this Bond bond)
    {
        var start = bond.Atom1.Location;
        var end = bond.Atom2.Location;
        var loc = Vector3.Lerp(start, end, .5f);

        var up = new Vector3(0, 1, 0);
        var line = end - start;
        var axis = Vector3.Cross(up, line);
        var rad = MathF.Acos(Vector3.Dot(up, Vector3.Normalize(line)));
        var quat = Quaternion.CreateFromAxisAngle(Vector3.Normalize(axis), rad);

        return (loc, quat);
    }
}