VoxelEngine/src/maths/rays.cpp

#include "rays.hpp"

#include "aabb.hpp"
#include <glm/glm.hpp>

static const rayvec3 X_AXIS = rayvec3(1, 0, 0), Y_AXIS = rayvec3(0, 1, 0),
                     Z_AXIS = rayvec3(0, 0, 1);

Ray::Ray(const rayvec3& origin, const rayvec3& dir) : origin(origin), dir(dir) {
}

// make faces from AABB
AABBFaces::AABBFaces(const rayvec3& parentBoxPos, const AABB& parentBox) {
    rayvec3 pbMin = parentBox.min(
            ),  // every face is min-point and opposite corner point
        pbMax = parentBox.max(), pbRealPos = parentBoxPos + pbMin;
    rayvec2 yzMax = rayvec2(parentBoxPos.y + pbMax.y, parentBoxPos.z + pbMax.z),
            xzMax = rayvec2(parentBoxPos.x + pbMax.x, parentBoxPos.z + pbMax.z),
            xyMax = rayvec2(parentBoxPos.x + pbMax.x, parentBoxPos.y + pbMax.y);
    faces[0] = {parentBoxPos + rayvec3(pbMax.x, pbMin.y, pbMin.z), yzMax};

    faces[1] = {pbRealPos, yzMax};

    faces[2] = {parentBoxPos + rayvec3(pbMin.x, pbMax.y, pbMin.z), xzMax};

    faces[3] = {pbRealPos, xzMax};

    faces[4] = {parentBoxPos + rayvec3(pbMin.x, pbMin.y, pbMax.z), xyMax};

    faces[5] = {pbRealPos, xyMax};
}

RayRelation Ray::intersectYZFace(
    const rayvec3& faceMin,
    const rayvec2&
        faceOppositeCorner,  // y and z global coords of opposite corner
    glm::ivec3& normal_ret,
    scalar_t& distance_ret  // sinonym of rayCoef
) {
    if (fabs(glm::dot(dir, X_AXIS)) < 1.0E-8) {  // precision
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.x - origin.x) /
                       (dir.x);  // equivalent to distance if dir normalized
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        faceMin.x, rayCoef * dir.y + origin.y, rayCoef * dir.z + origin.z};

    if (intersectPoint.y >= faceMin.y &&
        intersectPoint.y <= faceOppositeCorner[0] &&
        intersectPoint.z >= faceMin.z &&
        intersectPoint.z <= faceOppositeCorner[1]) {
        distance_ret = rayCoef;  // believe that dir normalized
        if (dir.x > 0)
            normal_ret = -X_AXIS;
        else
            normal_ret = X_AXIS;
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::intersectXZFace(
    const rayvec3& faceMin,
    const rayvec2&
        faceOppositeCorner,  // x and z global coords of opposite corner
    glm::ivec3& normal_ret,
    scalar_t& distance_ret
) {
    if (fabs(glm::dot(dir, Y_AXIS)) < 1.0E-8) {  // precision
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.y - origin.y) /
                       (dir.y);  // equivalent to distance if dir normalized
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        rayCoef * dir.x + origin.x, faceMin.y, rayCoef * dir.z + origin.z};

    if (intersectPoint.x >= faceMin.x  // Face-hit check
        && intersectPoint.x <= faceOppositeCorner[0] &&
        intersectPoint.z >= faceMin.z &&
        intersectPoint.z <= faceOppositeCorner[1]) {
        distance_ret = rayCoef;  // believe that dir normalized
        if (dir.y > 0)
            normal_ret = -Y_AXIS;
        else
            normal_ret = Y_AXIS;
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::intersectXYFace(
    const rayvec3& faceMin,
    const rayvec2&
        faceOppositeCorner,  // x and y global coords of opposite corner
    glm::ivec3& normal_ret,
    scalar_t& distance_ret
) {
    if (fabs(glm::dot(dir, Z_AXIS)) < 1.0E-8) {  // precision
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.z - origin.z) /
                       (dir.z);  // equivalent to distance if dir normalized
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        rayCoef * dir.x + origin.x, rayCoef * dir.y + origin.y, faceMin.z};

    if (intersectPoint.x >= faceMin.x  // Face-hit check
        && intersectPoint.x <= faceOppositeCorner[0] &&
        intersectPoint.y >= faceMin.y &&
        intersectPoint.y <= faceOppositeCorner[1]) {
        distance_ret = rayCoef;  // believe that dir normalized
        if (dir.z > 0)
            normal_ret = -Z_AXIS;
        else
            normal_ret = Z_AXIS;
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::isIntersectsYZFace(
    const rayvec3& faceMin, const rayvec2& faceOppositeCorner
) {
    if (fabs(glm::dot(dir, X_AXIS)) < 1.0E-8) {  // precision of "parallelity"
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.x - origin.x) / (dir.x);
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        faceMin.x, rayCoef * dir.y + origin.y, rayCoef * dir.z + origin.z};

    if (intersectPoint.y >= faceMin.y &&
        intersectPoint.y <= faceOppositeCorner[0] &&
        intersectPoint.z >= faceMin.z &&
        intersectPoint.z <= faceOppositeCorner[1]) {
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::isIntersectsXZFace(
    const rayvec3& faceMin, const rayvec2& faceOppositeCorner
) {
    if (fabs(glm::dot(dir, Y_AXIS)) < 1.0E-8) {  // precision of "parallelity"
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.y - origin.y) / (dir.y);
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        rayCoef * dir.x + origin.x, faceMin.y, rayCoef * dir.z + origin.z};

    if (intersectPoint.x >= faceMin.x  // Face-hit check
        && intersectPoint.x <= faceOppositeCorner[0] &&
        intersectPoint.z >= faceMin.z &&
        intersectPoint.z <= faceOppositeCorner[1]) {
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::isIntersectsXYFace(
    const rayvec3& faceMin, const rayvec2& faceOppositeCorner
) {
    if (fabs(glm::dot(dir, Z_AXIS)) < 1.0E-8) {  // precision of "parallelity"
        return RayRelation::Parallel;
    }

    scalar_t rayCoef = (faceMin.z - origin.z) / (dir.z);
    if (rayCoef < 0) return RayRelation::None;
    rayvec3 intersectPoint = {
        rayCoef * dir.x + origin.x, rayCoef * dir.y + origin.y, faceMin.z};

    if (intersectPoint.x >= faceMin.x  // Face-hit check
        && intersectPoint.x <= faceOppositeCorner[0] &&
        intersectPoint.y >= faceMin.y &&
        intersectPoint.y <= faceOppositeCorner[1]) {
        return RayRelation::Intersect;
    }
    return RayRelation::None;
}

RayRelation Ray::intersectAABB(
    const rayvec3& boxPos,
    const AABB& box,
    float maxDist,
    glm::ivec3& normal_ret,
    scalar_t& distance_ret
) {
    const AABBFaces& boxFaces = AABBFaces(boxPos, box);
    return intersectAABBFaces(boxFaces, maxDist, normal_ret, distance_ret);
}

RayRelation Ray::intersectAABBFaces(
    const AABBFaces& boxFaces,
    float maxDist,
    glm::ivec3& normal_ret,
    scalar_t& distance_ret
) {
    scalar_t faceDist;
    distance_ret = maxDist;
    glm::ivec3 bufNormal;
    // unsigned char intersectedCount = 0; //this code is very uncomfortable,
    // DONT LEARN IT!
    bool isIntersect = false;

    if (intersectYZFace(
            boxFaces.faces[0].first,
            boxFaces.faces[0].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (intersectYZFace(
            boxFaces.faces[1].first,
            boxFaces.faces[1].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (intersectXZFace(
            boxFaces.faces[2].first,
            boxFaces.faces[2].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (intersectXZFace(
            boxFaces.faces[3].first,
            boxFaces.faces[3].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (intersectXYFace(
            boxFaces.faces[4].first,
            boxFaces.faces[4].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (intersectXYFace(
            boxFaces.faces[5].first,
            boxFaces.faces[5].second,
            bufNormal,
            faceDist
        ) > RayRelation::None &&
        faceDist < distance_ret) {
        isIntersect = true;
        normal_ret = bufNormal;
        distance_ret = faceDist;
    }

    if (isIntersect) return RayRelation::Intersect;
    return RayRelation::None;
}