SchemaExtensions.cs

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using GLTF;
using GLTF.Schema;
using UnityEngine;

namespace UnityGLTF.Extensions
{
    public static class SchemaExtensions
    {
        // glTF matrix: column vectors, column-major storage, +Y up, +Z forward, -X right, right-handed
        // unity matrix: column vectors, column-major storage, +Y up, +Z forward, +X right, left-handed
        // multiply by a negative X scale to convert handedness
        public static readonly GLTF.Math.Vector3 CoordinateSpaceConversionScale = new GLTF.Math.Vector3(-1, 1, 1);
        public static bool CoordinateSpaceConversionRequiresHandednessFlip
        {
            get
            {
                return CoordinateSpaceConversionScale.X * CoordinateSpaceConversionScale.Y * CoordinateSpaceConversionScale.Z < 0.0f;
            }
        }

        public static readonly GLTF.Math.Vector4 TangentSpaceConversionScale = new GLTF.Math.Vector4(-1, 1, 1, -1);

        public static void GetUnityTRSProperties(this Node node, out Vector3 position, out Quaternion rotation,
            out Vector3 scale)
        {
            if (!node.UseTRS)
            {
                Matrix4x4 unityMat = node.Matrix.ToUnityMatrix4x4Convert();
                unityMat.GetTRSProperties(out position, out rotation, out scale);
            }
            else
            {
                position = node.Translation.ToUnityVector3Convert();
                rotation = node.Rotation.ToUnityQuaternionConvert();
                scale = node.Scale.ToUnityVector3Raw();
            }
        }

        public static void SetUnityTransform(this Node node, Transform transform)
        {
            node.Translation = transform.localPosition.ToGltfVector3Convert();
            node.Rotation = transform.localRotation.ToGltfQuaternionConvert();
            node.Scale = transform.localScale.ToGltfVector3Raw();
        }

        // todo: move to utility class
        public static void GetTRSProperties(this Matrix4x4 mat, out Vector3 position, out Quaternion rotation,
            out Vector3 scale)
        {
            position = mat.GetColumn(3);

            Vector3 x = mat.GetColumn(0);
            Vector3 y = mat.GetColumn(1);
            Vector3 z = mat.GetColumn(2);
            Vector3 calculatedZ = Vector3.Cross(x, y);
            bool mirrored = Vector3.Dot(calculatedZ, z) < 0.0f;

            scale = new Vector3(x.magnitude * (mirrored ? -1.0f : 1.0f), y.magnitude, z.magnitude);

            rotation = Quaternion.LookRotation(mat.GetColumn(2), mat.GetColumn(1));
        }

        public static void GetTRSProperties(this GLTF.Math.Matrix4x4 gltfMat, out Vector3 position, out Quaternion rotation,
            out Vector3 scale)
        {
            gltfMat.ToUnityMatrix4x4Convert().GetTRSProperties(out position, out rotation, out scale);
        }

        public static GLTF.Math.Vector4 GetColumn(this GLTF.Math.Matrix4x4 mat, uint columnNum)
        {
            switch (columnNum)
            {
                case 0:
                    {
                        return new GLTF.Math.Vector4(mat.M11, mat.M21, mat.M31, mat.M41);
                    }
                case 1:
                    {
                        return new GLTF.Math.Vector4(mat.M12, mat.M22, mat.M32, mat.M42);
                    }
                case 2:
                    {
                        return new GLTF.Math.Vector4(mat.M13, mat.M23, mat.M33, mat.M43);
                    }
                case 3:
                    {
                        return new GLTF.Math.Vector4(mat.M14, mat.M24, mat.M34, mat.M44);
                    }
                default:
                    throw new System.Exception("column num is out of bounds");
            }
        }

        public static Quaternion ToUnityQuaternionConvert(this GLTF.Math.Quaternion gltfQuat)
        {
            // get raw matrix conversion (gltf matrix stored in a unity matrix for easier math)
            Vector3 origAxis = new Vector3(gltfQuat.X, gltfQuat.Y, gltfQuat.Z);
            float axisFlipScale = CoordinateSpaceConversionRequiresHandednessFlip ? -1.0f : 1.0f;
            Vector3 newAxis = axisFlipScale * Vector3.Scale(origAxis, CoordinateSpaceConversionScale.ToUnityVector3Raw());

            // then put the quaternion back together and return it
            return new Quaternion(newAxis.x, newAxis.y, newAxis.z, gltfQuat.W);
        }

        public static GLTF.Math.Quaternion ToGltfQuaternionConvert(this Quaternion unityQuat)
        {
            // get the original axis and apply conversion scale as well as potential rotation axis flip
            Vector3 origAxis = new Vector3(unityQuat.x, unityQuat.y, unityQuat.z);
            float axisFlipScale = CoordinateSpaceConversionRequiresHandednessFlip ? -1.0f : 1.0f;
            Vector3 newAxis = axisFlipScale * Vector3.Scale(origAxis, CoordinateSpaceConversionScale.ToUnityVector3Raw());

            // then put the quaternion back together and return it
            return new GLTF.Math.Quaternion(newAxis.x, newAxis.y, newAxis.z, unityQuat.w);
        }

        public static Matrix4x4 ToUnityMatrix4x4Convert(this GLTF.Math.Matrix4x4 gltfMat)
        {
            Matrix4x4 rawUnityMat = gltfMat.ToUnityMatrix4x4Raw();
            Vector3 coordinateSpaceConversionScale = CoordinateSpaceConversionScale.ToUnityVector3Raw();
            Matrix4x4 convert = Matrix4x4.Scale(coordinateSpaceConversionScale);
            Matrix4x4 unityMat = convert * rawUnityMat * convert;
            return unityMat;
        }

        public static GLTF.Math.Matrix4x4 ToGltfMatrix4x4Convert(this Matrix4x4 unityMat)
        {
            Vector3 coordinateSpaceConversionScale = CoordinateSpaceConversionScale.ToUnityVector3Raw();
            Matrix4x4 convert = Matrix4x4.Scale(coordinateSpaceConversionScale);
            GLTF.Math.Matrix4x4 gltfMat = (convert * unityMat * convert).ToGltfMatrix4x4Raw();
            return gltfMat;
        }

        public static Vector3 ToUnityVector3Convert(this GLTF.Math.Vector3 gltfVec3)
        {
            Vector3 coordinateSpaceConversionScale = CoordinateSpaceConversionScale.ToUnityVector3Raw();
            Vector3 unityVec3 = Vector3.Scale(gltfVec3.ToUnityVector3Raw(), coordinateSpaceConversionScale);
            return unityVec3;
        }

        public static GLTF.Math.Vector3 ToGltfVector3Convert(this Vector3 unityVec3)
        {
            Vector3 coordinateSpaceConversionScale = CoordinateSpaceConversionScale.ToUnityVector3Raw();
            GLTF.Math.Vector3 gltfVec3 = Vector3.Scale(unityVec3, coordinateSpaceConversionScale).ToGltfVector3Raw();
            return gltfVec3;
        }

        public static GLTF.Math.Vector3 ToGltfVector3Raw(this Vector3 unityVec3)
        {
            GLTF.Math.Vector3 gltfVec3 = new GLTF.Math.Vector3(unityVec3.x, unityVec3.y, unityVec3.z);
            return gltfVec3;
        }

        public static GLTF.Math.Vector4 ToGltfVector4Raw(this Vector4 unityVec4)
        {
            GLTF.Math.Vector4 gltfVec4 = new GLTF.Math.Vector4(unityVec4.x, unityVec4.y, unityVec4.z, unityVec4.w);
            return gltfVec4;
        }

        public static Matrix4x4 ToUnityMatrix4x4Raw(this GLTF.Math.Matrix4x4 gltfMat)
        {
            Vector4 rawUnityCol0 = gltfMat.GetColumn(0).ToUnityVector4Raw();
            Vector4 rawUnityCol1 = gltfMat.GetColumn(1).ToUnityVector4Raw();
            Vector4 rawUnityCol2 = gltfMat.GetColumn(2).ToUnityVector4Raw();
            Vector4 rawUnityCol3 = gltfMat.GetColumn(3).ToUnityVector4Raw();
            Matrix4x4 rawUnityMat = new UnityEngine.Matrix4x4();
            rawUnityMat.SetColumn(0, rawUnityCol0);
            rawUnityMat.SetColumn(1, rawUnityCol1);
            rawUnityMat.SetColumn(2, rawUnityCol2);
            rawUnityMat.SetColumn(3, rawUnityCol3);

            return rawUnityMat;
        }

        public static GLTF.Math.Matrix4x4 ToGltfMatrix4x4Raw(this Matrix4x4 unityMat)
        {
            GLTF.Math.Vector4 c0 = unityMat.GetColumn(0).ToGltfVector4Raw();
            GLTF.Math.Vector4 c1 = unityMat.GetColumn(1).ToGltfVector4Raw();
            GLTF.Math.Vector4 c2 = unityMat.GetColumn(2).ToGltfVector4Raw();
            GLTF.Math.Vector4 c3 = unityMat.GetColumn(3).ToGltfVector4Raw();
            GLTF.Math.Matrix4x4 rawGltfMat = new GLTF.Math.Matrix4x4(c0.X, c0.Y, c0.Z, c0.W, c1.X, c1.Y, c1.Z, c1.W, c2.X, c2.Y, c2.Z, c2.W, c3.X, c3.Y, c3.Z, c3.W);
            return rawGltfMat;
        }

        public static Vector2 ToUnityVector2Raw(this GLTF.Math.Vector2 vec2)
        {
            return new Vector2(vec2.X, vec2.Y);
        }

        public static Vector2[] ToUnityVector2Raw(this GLTF.Math.Vector2[] inVecArr)
        {
            Vector2[] outVecArr = new Vector2[inVecArr.Length];
            for (int i = 0; i < inVecArr.Length; ++i)
            {
                outVecArr[i] = inVecArr[i].ToUnityVector2Raw();
            }
            return outVecArr;
        }

        public static Vector3 ToUnityVector3Raw(this GLTF.Math.Vector3 vec3)
        {
            return new Vector3(vec3.X, vec3.Y, vec3.Z);
        }

        public static Vector3[] ToUnityVector3Raw(this GLTF.Math.Vector3[] inVecArr)
        {
            Vector3[] outVecArr = new Vector3[inVecArr.Length];
            for (int i = 0; i < inVecArr.Length; ++i)
            {
                outVecArr[i] = inVecArr[i].ToUnityVector3Raw();
            }
            return outVecArr;
        }

        public static Vector4 ToUnityVector4Raw(this GLTF.Math.Vector4 vec4)
        {
            return new Vector4(vec4.X, vec4.Y, vec4.Z, vec4.W);
        }

        public static Vector4[] ToUnityVector4Raw(this GLTF.Math.Vector4[] inVecArr)
        {
            Vector4[] outVecArr = new Vector4[inVecArr.Length];
            for (int i = 0; i < inVecArr.Length; ++i)
            {
                outVecArr[i] = inVecArr[i].ToUnityVector4Raw();
            }
            return outVecArr;
        }

        public static UnityEngine.Color ToUnityColorRaw(this GLTF.Math.Color color)
        {
            return new UnityEngine.Color(color.R, color.G, color.B, color.A);
        }

        public static GLTF.Math.Color ToNumericsColorRaw(this UnityEngine.Color color)
        {
            return new GLTF.Math.Color(color.r, color.g, color.b, color.a);
        }

        public static UnityEngine.Color[] ToUnityColorRaw(this GLTF.Math.Color[] inColorArr)
        {
            UnityEngine.Color[] outColorArr = new UnityEngine.Color[inColorArr.Length];
            for (int i = 0; i < inColorArr.Length; ++i)
            {
                outColorArr[i] = inColorArr[i].ToUnityColorRaw();
            }
            return outColorArr;
        }

        public static int[] ToIntArrayRaw(this uint[] uintArr)
        {
            int[] intArr = new int[uintArr.Length];
            for (int i = 0; i < uintArr.Length; ++i)
            {
                uint uintVal = uintArr[i];
                Debug.Assert(uintVal <= int.MaxValue);
                intArr[i] = (int)uintVal;
            }

            return intArr;
        }

        public static GLTF.Math.Quaternion ToGltfQuaternionRaw(this Quaternion unityQuat)
        {
            return new GLTF.Math.Quaternion(unityQuat.x, unityQuat.y, unityQuat.z, unityQuat.w);
        }

        public static Quaternion ToUnityQuaternionRaw(this GLTF.Math.Quaternion quaternion)
        {
            return new Quaternion(quaternion.X, quaternion.Y, quaternion.Z, quaternion.W);
        }

        public static void FlipTexCoordArrayV(ref AttributeAccessor attributeAccessor)
        {
            for (var i = 0; i < attributeAccessor.AccessorContent.AsVec2s.Length; i++)
            {
                attributeAccessor.AccessorContent.AsVec2s[i].Y = 1.0f - attributeAccessor.AccessorContent.AsVec2s[i].Y;
            }
        }

        public static UnityEngine.Vector2[] FlipTexCoordArrayVAndCopy(UnityEngine.Vector2[] array)
        {
            var returnArray = new UnityEngine.Vector2[array.Length];

            for (var i = 0; i < array.Length; i++)
            {
                returnArray[i].x = array[i].x;
                returnArray[i].y = 1.0f - array[i].y;
            }

            return returnArray;
        }

        public static void ConvertVector3CoordinateSpace(ref AttributeAccessor attributeAccessor, GLTF.Math.Vector3 coordinateSpaceCoordinateScale)
        {
            for (int i = 0; i < attributeAccessor.AccessorContent.AsVertices.Length; i++)
            {
                attributeAccessor.AccessorContent.AsVertices[i].X *= coordinateSpaceCoordinateScale.X;
                attributeAccessor.AccessorContent.AsVertices[i].Y *= coordinateSpaceCoordinateScale.Y;
                attributeAccessor.AccessorContent.AsVertices[i].Z *= coordinateSpaceCoordinateScale.Z;
            }
        }

        public static UnityEngine.Vector3[] ConvertVector3CoordinateSpaceAndCopy(Vector3[] array, GLTF.Math.Vector3 coordinateSpaceCoordinateScale)
        {
            var returnArray = new UnityEngine.Vector3[array.Length];

            for (int i = 0; i < array.Length; i++)
            {
                returnArray[i].x = array[i].x * coordinateSpaceCoordinateScale.X;
                returnArray[i].y = array[i].z * coordinateSpaceCoordinateScale.Y;
                returnArray[i].z = array[i].y * coordinateSpaceCoordinateScale.Z;
            }

            return returnArray;
        }

        public static void ConvertVector4CoordinateSpace(ref AttributeAccessor attributeAccessor, GLTF.Math.Vector4 coordinateSpaceCoordinateScale)
        {
            for (int i = 0; i < attributeAccessor.AccessorContent.AsVec4s.Length; i++)
            {
                attributeAccessor.AccessorContent.AsVec4s[i].X *= coordinateSpaceCoordinateScale.X;
                attributeAccessor.AccessorContent.AsVec4s[i].Y *= coordinateSpaceCoordinateScale.Y;
                attributeAccessor.AccessorContent.AsVec4s[i].Z *= coordinateSpaceCoordinateScale.Z;
                attributeAccessor.AccessorContent.AsVec4s[i].W *= coordinateSpaceCoordinateScale.W;
            }
        }

        public static Vector4[] ConvertVector4CoordinateSpaceAndCopy(Vector4[] array, GLTF.Math.Vector4 coordinateSpaceCoordinateScale)
        {
            var returnArray = new Vector4[array.Length];

            for (var i = 0; i < array.Length; i++)
            {
                returnArray[i].x *= coordinateSpaceCoordinateScale.X;
                returnArray[i].y *= coordinateSpaceCoordinateScale.Y;
                returnArray[i].z *= coordinateSpaceCoordinateScale.Z;
                returnArray[i].w *= coordinateSpaceCoordinateScale.W;
            }

            return returnArray;
        }

        public static void FlipFaces(ref AttributeAccessor attributeAccessor)
        {
            for (int i = 0; i < attributeAccessor.AccessorContent.AsTriangles.Length; i += 3)
            {
                uint temp = attributeAccessor.AccessorContent.AsUInts[i];
                attributeAccessor.AccessorContent.AsUInts[i] = attributeAccessor.AccessorContent.AsUInts[i + 2];
                attributeAccessor.AccessorContent.AsUInts[i + 2] = temp;
            }
        }

        public static int[] FlipFacesAndCopy(int[] triangles)
        {
            int[] returnArr = new int[triangles.Length];
            for (int i = 0; i < triangles.Length; i += 3)
            {
                int temp = triangles[i];
                returnArr[i] = triangles[i + 2];
                returnArr[i + 1] = triangles[i + 1];
                returnArr[i + 2] = temp;
            }

            return returnArr;
        }
    }
}