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;
}