Crafter.Math/interfaces/Crafter.Math-Intersection.cppm

/*
Crafter®.Math
Copyright (C) 2026 Catcrafts®
catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

export module Crafter.Math:Intersection;
import :Vector;
import :MatrixRowMajor;
import std;

namespace Crafter {
    export template<typename T>
	constexpr T IntersectionTestRayTriangle(Vector<T, 3, 0> vert0, Vector<T, 3, 0> vert1, Vector<T, 3, 0> vert2, Vector<T, 3, 0> rayOrigin, Vector<T, 3, 0> rayDir) {
        Vector<T, 3, 0> edge1 = vert1 - vert0;
        Vector<T, 3, 0> edge2 = vert2 - vert0;

        Vector<T, 3, 0> h = Vector<T, 3, 0>::Cross(rayDir, edge2);
        T determinant = Vector<T, 3, 0>::Dot(edge1, h);

        if (determinant <= std::numeric_limits<T>::epsilon())  {
            return std::numeric_limits<T>::max();
        }

        T inverse_determinant = T(1) / determinant;

        Vector<T, 3, 0> origins_diff_vector = rayOrigin - vert0;
        T u =  Vector<T, 3, 0>::Dot(origins_diff_vector, h) * inverse_determinant;

        if (u < 0.0 || u > 1.0)
        {
            return std::numeric_limits<T>::max();
        }

        Vector<T, 3, 0> q = Vector<T, 3, 0>::Cross(origins_diff_vector, edge1);
        T v = inverse_determinant * Vector<T, 3, 0>::Dot(rayDir, q);

        if (v < 0.0 || u + v > 1.0) {
            return std::numeric_limits<T>::max();
        }

        return inverse_determinant * Vector<T, 3, 0>::Dot(edge2, q);
    }

    export template<typename T>
    constexpr T IntersectionTestRaySphere(Vector<T, 3, 0> position, T radius, Vector<T, 3, 0> rayOrigin, Vector<T, 3, 0> rayDir) {
        T a = Vector<T, 3, 0>::Dot(rayDir, rayDir);
        T b = Vector<T, 3, 0>::Dot(rayDir, (T(2) * (rayOrigin - position)));
        T c = Vector<T, 3, 0>::Dot(position, position) + Vector<T, 3, 0>::Dot(rayOrigin, rayOrigin) - T(2) * Vector<T, 3, 0>::Dot(rayOrigin, position) - radius * radius;
        T d = b * b + (T(-4)) * a * c;

        if (d < 0) {
            return std::numeric_limits<T>::max();
        }

        d = std::sqrt(d);

        T t = (T(-0.5)) * (b + d) / a;
        if (t > T(0)) {
            return t;
        } else {
            return std::numeric_limits<T>::max();
        }
    }

    export template<typename T>
    constexpr T IntersectionTestRayOrientedBox(Vector<T, 3, 0> boxPosition, Vector<T, 3, 0> boxSize, Vector<T, 4, 0> boxRotation, Vector<T, 3, 0> rayOrigin, Vector<T, 3, 0> rayDir) {
        Vector<T, 4, 0> invRot(
            -boxRotation.x,
            -boxRotation.y,
            -boxRotation.z,
            boxRotation.w
        );

        Vector<T, 3, 0> localOrigin = Vector<T, 3, 0>::Rotate(rayOrigin - boxPosition, invRot);
        Vector<T, 3, 0> localDir    = Vector<T, 3, 0>::Rotate(rayDir, invRot);

        Vector<T,3,0> halfExtents = boxSize * T(0.5);

        T tMin = T(0);
        T tMax = std::numeric_limits<T>::max();

        for (std::uint32_t i = 0; i < 3; ++i)
        {
            if (std::abs(localDir.v[i]) < std::numeric_limits<T>::epsilon())
            {
                if (localOrigin.v[i] < -halfExtents.v[i] || localOrigin.v[i] >  halfExtents.v[i]) {
                    return std::numeric_limits<T>::max();
                }
            }
            else
            {
                T invD = T(1) / localDir.v[i];
                T t1 = (-halfExtents.v[i] - localOrigin.v[i]) * invD;
                T t2 = ( halfExtents.v[i] - localOrigin.v[i]) * invD;

                if (t1 > t2) {
                    std::swap(t1, t2);
                }

                tMin = std::max(tMin, t1);
                tMax = std::min(tMax, t2);

                if (tMin > tMax) {
                    return std::numeric_limits<T>::max();
                }
            }
        }

        return (tMin >= T(0)) ? tMin : tMax;
    }


    export template<typename T>
    std::vector<Vector<T, 3, 0>> getOBBCorners(Vector<T, 3, 0> size, MatrixRowMajor<T, 4, 3, 1> matrix) {
        std::vector<Vector<T, 3, 0>> localCorners = {
            Vector<T, 3, 0>(-size.x, -size.y, -size.z),
            Vector<T, 3, 0>( size.x, -size.y, -size.z),
            Vector<T, 3, 0>(-size.x,  size.y, -size.z),
            Vector<T, 3, 0>( size.x,  size.y, -size.z),
            Vector<T, 3, 0>(-size.x, -size.y,  size.z),
            Vector<T, 3, 0>( size.x, -size.y,  size.z),
            Vector<T, 3, 0>(-size.x,  size.y,  size.z),
            Vector<T, 3, 0>( size.x,  size.y,  size.z)
        };
        
        std::vector<Vector<T, 3, 0>> worldCorners;
        
        for (Vector<T, 3, 0> localCorner : localCorners) {
            Vector<T, 3, 0> rotatedCorner = matrix * localCorner;
            worldCorners.push_back(rotatedCorner);
        }

        return worldCorners;
    }

    export template<typename T>
    constexpr bool IntersectionTestOrientedBoxOrientedBox(Vector<T, 3, 0> sizeA, MatrixRowMajor<T, 4, 3, 1> boxA, Vector<T, 3, 0> sizeB, MatrixRowMajor<T, 4, 3, 1> boxB) {
        std::vector<Vector<T, 3, 0>> axes;

        std::vector<Vector<T, 3, 0>> box1Corners = getOBBCorners(sizeA, boxA);
        std::vector<Vector<T, 3, 0>> box2Corners = getOBBCorners(sizeB, boxB);

        axes.push_back(Vector<T, 3, 0>(boxA.m[0][0], boxA.m[0][1], boxA.m[0][2]));
        axes.push_back(Vector<T, 3, 0>(boxA.m[1][0], boxA.m[1][1], boxA.m[1][2]));
        axes.push_back(Vector<T, 3, 0>(boxA.m[2][0], boxA.m[2][1], boxA.m[2][2]));
        
        axes.push_back(Vector<T, 3, 0>(boxB.m[0][0], boxB.m[0][1], boxB.m[0][2]));
        axes.push_back(Vector<T, 3, 0>(boxB.m[1][0], boxB.m[1][1], boxB.m[1][2]));
        axes.push_back(Vector<T, 3, 0>(boxB.m[2][0], boxB.m[2][1], boxB.m[2][2]));
        
        for (int i = 0; i < 3; ++i) {
            for (int j = 0; j < 3; ++j) {
                axes.push_back(Vector<T, 3, 0>::Normalize(Vector<T, 3, 0>::Cross(Vector<T, 3, 0>(boxA.m[i][0], boxA.m[i][1], boxA.m[i][2]), Vector<T, 3, 0>(boxB.m[j][0], boxB.m[j][1], boxB.m[j][2]))));
            }
        }

        for (Vector<T, 3, 0> axis : axes) {
            T min1 = Vector<T, 3, 0>::Dot(box1Corners[0], axis);
            T max1 = min1;
            for (Vector<T, 3, 0> corner : box1Corners) {
                T projection = Vector<T, 3, 0>::Dot(corner, axis);
                min1 = std::min(min1, projection);
                max1 = std::max(max1, projection);
            }

            T min2 = Vector<T, 3, 0>::Dot(box2Corners[0], axis);
            T max2 = min2;
            for (Vector<T, 3, 0> corner : box2Corners) {
                T projection = Vector<T, 3, 0>::Dot(corner, axis);
                min2 = std::min(min2, projection);
                max2 = std::max(max2, projection);
            }

            if (max1 < min2 || max2 < min1) {
                return false;
            }
        }

        return true;
    }

    export template<typename T>
    constexpr bool IntersectionTestSphereOrientatedBox(Vector<T, 3, 0> spherePos, T sphereRadius, Vector<T, 3, 0> boxSize, MatrixRowMajor<T, 4, 3, 1> boxMat) {
        Vector<T, 3, 0> d = spherePos - Vector<T, 3, 0>(boxMat.m[0][3], boxMat.m[1][3], boxMat.m[2][3]);

        T distSq = 0.0f;

        for (std::uint32_t i = 0; i < 3; ++i)
        {
            Vector<T, 3, 0> axis(boxMat.m[0][i], boxMat.m[1][i], boxMat.m[2][i]);
            T dist = Vector<T, 3, 0>::Dot(d, axis);
            T excess = std::fabs(dist) - boxSize.v[i];
            excess = std::max(excess, 0.0f);
            distSq += excess * excess;
        }

        return distSq <= sphereRadius * sphereRadius;
    }
}