Switch-Toolbox/Switch_Toolbox_Library/FileFormats/Assimp/AssimpHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Assimp;
using OpenTK;

namespace Switch_Toolbox.Library
{
    public class AssimpHelper
    {
        public static OpenTK.Matrix4 TKMatrix(Assimp.Matrix4x4 input)
        {
            return new OpenTK.Matrix4(input.A1, input.B1, input.C1, input.D1,
                                       input.A2, input.B2, input.C2, input.D2,
                                       input.A3, input.B3, input.C3, input.D3,
                                       input.A4, input.B4, input.C4, input.D4);
        }
        public static OpenTK.Quaternion TKQuaternion(Assimp.Quaternion rot)
        {
            OpenTK.Quaternion quat = new OpenTK.Quaternion();
            quat.X = rot.X;
            quat.Y = rot.Y;
            quat.Z = rot.Z;
            quat.W = rot.W;
            return quat;
        }

        public static Vector3 ToEulerAngles(Assimp.Quaternion q)
        {
            float PI = (float)Math.PI;
            // Store the Euler angles in radians
            Vector3 pitchYawRoll = new Vector3();

            double sqw = q.W * q.W;
            double sqx = q.X * q.X;
            double sqy = q.Y * q.Y;
            double sqz = q.Z * q.Z;

            // If quaternion is normalised the unit is one, otherwise it is the correction factor
            double unit = sqx + sqy + sqz + sqw;
            double test = q.X * q.Y + q.Z * q.W;

            if (test > 0.499f * unit)
            {
                // Singularity at north pole
                pitchYawRoll.Y = 2f * (float)Math.Atan2(q.X, q.W);  // Yaw
                pitchYawRoll.X = PI * 0.5f;                         // Pitch
                pitchYawRoll.Z = 0f;                                // Roll
                return pitchYawRoll;
            }
            else if (test < -0.499f * unit)
            {
                // Singularity at south pole
                pitchYawRoll.Y = -2f * (float)Math.Atan2(q.X, q.W); // Yaw
                pitchYawRoll.X = -PI * 0.5f;                        // Pitch
                pitchYawRoll.Z = 0f;                                // Roll
                return pitchYawRoll;
            }
            pitchYawRoll.Y = (float)Math.Atan2(2 * q.Y * q.W - 2 * q.X * q.Z, sqx - sqy - sqz + sqw);       // Yaw
            pitchYawRoll.X = (float)Math.Asin(2 * test / unit);                                             // Pitch
            pitchYawRoll.Z = (float)Math.Atan2(2 * q.X * q.W - 2 * q.Y * q.Z, -sqx + sqy - sqz + sqw);      // Roll
            return pitchYawRoll;
        }
    }
}