//
//  AABox.cpp
//  libraries/octree/src
//
//  Created by Brad Hefta-Gaub on 04/11/13.
//  Copyright 2013 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#include "AABox.h"

#include "AACube.h"
#include "Transform.h"
#include "Extents.h"
#include "GeometryUtil.h"
#include "NumericalConstants.h"

const glm::vec3 AABox::INFINITY_VECTOR(std::numeric_limits<float>::infinity());

AABox::AABox(const AACube& other) :
    _corner(other.getCorner()), _scale(other.getScale(), other.getScale(), other.getScale()) {
}

AABox::AABox(const Extents& other) :
    _corner(other.minimum),
    _scale(other.maximum - other.minimum) {
}

AABox::AABox(const glm::vec3& corner, float size) :
    _corner(corner), _scale(size, size, size) {
};

AABox::AABox(const glm::vec3& corner, const glm::vec3& dimensions) :
    _corner(corner), _scale(dimensions) {
};

AABox::AABox() : _corner(INFINITY_VECTOR), _scale(0.0f) {
};

glm::vec3 AABox::calcCenter() const {
    glm::vec3 center(_corner);
    center += (_scale * 0.5f);
    return center;
}

glm::vec3 AABox::getVertex(BoxVertex vertex) const {
    switch (vertex) {
        case BOTTOM_LEFT_NEAR:
            return _corner + glm::vec3(_scale.x, 0, 0);
        case BOTTOM_RIGHT_NEAR:
            return _corner;
        case TOP_RIGHT_NEAR:
            return _corner + glm::vec3(0, _scale.y, 0);
        case TOP_LEFT_NEAR:
            return _corner + glm::vec3(_scale.x, _scale.y, 0);
        case BOTTOM_LEFT_FAR:
            return _corner + glm::vec3(_scale.x, 0, _scale.z);
        case BOTTOM_RIGHT_FAR:
            return _corner + glm::vec3(0, 0, _scale.z);
        case TOP_RIGHT_FAR:
            return _corner + glm::vec3(0, _scale.y, _scale.z);
        default: //quiet windows warnings
        case TOP_LEFT_FAR:
            return _corner + _scale;
    }
}

void AABox::setBox(const glm::vec3& corner, float scale) {
    _corner = corner;
    _scale = glm::vec3(scale, scale, scale);
}

void AABox::setBox(const glm::vec3& corner, const glm::vec3& scale) {
    _corner = corner;
    _scale = scale;
}

glm::vec3 AABox::getFarthestVertex(const glm::vec3& normal) const {
    glm::vec3 result = _corner;
    // This is a branchless version of:
    //if (normal.x > 0.0f) {
    //    result.x += _scale.x;
    //}
    //if (normal.y > 0.0f) {
    //    result.y += _scale.y;
    //}
    //if (normal.z > 0.0f) {
    //    result.z += _scale.z;
    //}
    float blend = (float)(normal.x > 0.0f);
    result.x += blend * _scale.x + (1.0f - blend) * 0.0f;
    blend = (float)(normal.y > 0.0f);
    result.y += blend * _scale.y + (1.0f - blend) * 0.0f;
    blend = (float)(normal.z > 0.0f);
    result.z += blend * _scale.z + (1.0f - blend) * 0.0f;
    return result;
}

glm::vec3 AABox::getNearestVertex(const glm::vec3& normal) const {
    glm::vec3 result = _corner;
    // This is a branchless version of:
    //if (normal.x < 0.0f) {
    //    result.x += _scale.x;
    //}
    //if (normal.y < 0.0f) {
    //    result.y += _scale.y;
    //}
    //if (normal.z < 0.0f) {
    //    result.z += _scale.z;
    //}
    float blend = (float)(normal.x < 0.0f);
    result.x += blend * _scale.x + (1.0f - blend) * 0.0f;
    blend = (float)(normal.y < 0.0f);
    result.y += blend * _scale.y + (1.0f - blend) * 0.0f;
    blend = (float)(normal.z < 0.0f);
    result.z += blend * _scale.z + (1.0f - blend) * 0.0f;
    return result;
}

bool AABox::contains(const Triangle& triangle) const {
    return contains(triangle.v0) && contains(triangle.v1) && contains(triangle.v2);
}

bool AABox::contains(const glm::vec3& point) const {
    return aaBoxContains(point, _corner, _scale);
}

bool AABox::contains(const AABox& otherBox) const {
    for (int v = BOTTOM_LEFT_NEAR; v < TOP_LEFT_FAR; v++) {
        glm::vec3 vertex = otherBox.getVertex((BoxVertex)v);
        if (!contains(vertex)) {
            return false;
        }
    }
    return true;
}

bool AABox::touches(const AABox& otherBox) const {
    glm::vec3 relativeCenter = _corner - otherBox._corner + ((_scale - otherBox._scale) * 0.5f);

    glm::vec3 totalHalfScale = (_scale + otherBox._scale) * 0.5f;

    return fabsf(relativeCenter.x) <= totalHalfScale.x &&
        fabsf(relativeCenter.y) <= totalHalfScale.y &&
        fabsf(relativeCenter.z) <= totalHalfScale.z;
}

bool AABox::contains(const AACube& otherCube) const {
    for (int v = BOTTOM_LEFT_NEAR; v < TOP_LEFT_FAR; v++) {
        glm::vec3 vertex = otherCube.getVertex((BoxVertex)v);
        if (!contains(vertex)) {
            return false;
        }
    }
    return true;
}

bool AABox::touches(const AACube& otherCube) const {
    glm::vec3 relativeCenter = _corner - otherCube.getCorner() + ((_scale - otherCube.getDimensions()) * 0.5f);

    glm::vec3 totalHalfScale = (_scale + otherCube.getDimensions()) * 0.5f;

    return fabsf(relativeCenter.x) <= totalHalfScale.x &&
        fabsf(relativeCenter.y) <= totalHalfScale.y &&
        fabsf(relativeCenter.z) <= totalHalfScale.z;
}

// determines whether a value is within the expanded extents
static bool isWithinExpanded(float value, float corner, float size, float expansion) {
    return value >= corner - expansion && value <= corner + size + expansion;
}

bool AABox::expandedContains(const glm::vec3& point, float expansion) const {
    return isWithinExpanded(point.x, _corner.x, _scale.x, expansion) &&
        isWithinExpanded(point.y, _corner.y, _scale.y, expansion) &&
        isWithinExpanded(point.z, _corner.z, _scale.z, expansion);
}

bool AABox::expandedIntersectsSegment(const glm::vec3& start, const glm::vec3& end, float expansion) const {
    // handle the trivial cases where the expanded box contains the start or end
    if (expandedContains(start, expansion) || expandedContains(end, expansion)) {
        return true;
    }
    // check each axis
    glm::vec3 expandedCorner = _corner - glm::vec3(expansion, expansion, expansion);
    glm::vec3 expandedSize = _scale + glm::vec3(expansion, expansion, expansion) * 2.0f;
    glm::vec3 direction = end - start;
    float axisDistance;
    return (findIntersection(start.x, direction.x, expandedCorner.x, expandedSize.x, axisDistance) &&
                axisDistance >= 0.0f && axisDistance <= 1.0f &&
                isWithin(start.y + axisDistance*direction.y, expandedCorner.y, expandedSize.y) &&
                isWithin(start.z + axisDistance*direction.z, expandedCorner.z, expandedSize.z)) ||
           (findIntersection(start.y, direction.y, expandedCorner.y, expandedSize.y, axisDistance) &&
                axisDistance >= 0.0f && axisDistance <= 1.0f &&
                isWithin(start.x + axisDistance*direction.x, expandedCorner.x, expandedSize.x) &&
                isWithin(start.z + axisDistance*direction.z, expandedCorner.z, expandedSize.z)) ||
           (findIntersection(start.z, direction.z, expandedCorner.z, expandedSize.z, axisDistance) &&
                axisDistance >= 0.0f && axisDistance <= 1.0f &&
                isWithin(start.y + axisDistance*direction.y, expandedCorner.y, expandedSize.y) &&
                isWithin(start.x + axisDistance*direction.x, expandedCorner.x, expandedSize.x));
}

bool AABox::findRayIntersection(const glm::vec3& origin, const glm::vec3& direction, const glm::vec3& invDirection,
                                float& distance, BoxFace& face, glm::vec3& surfaceNormal) const {
    return findRayAABoxIntersection(origin, direction, invDirection, _corner, _scale, distance, face, surfaceNormal);
}

bool AABox::findParabolaIntersection(const glm::vec3& origin, const glm::vec3& velocity, const glm::vec3& acceleration,
                                     float& parabolicDistance, BoxFace& face, glm::vec3& surfaceNormal) const {
    return findParabolaAABoxIntersection(origin, velocity, acceleration, _corner, _scale, parabolicDistance, face, surfaceNormal);
}

bool AABox::rayHitsBoundingSphere(const glm::vec3& origin, const glm::vec3& direction) const {
    glm::vec3 localCenter = calcCenter() - origin;
    float distance = glm::dot(localCenter, direction);
    const float ONE_OVER_TWO_SQUARED = 0.25f;
    float radiusSquared = ONE_OVER_TWO_SQUARED * glm::length2(_scale);
    return (glm::length2(localCenter) < radiusSquared
            || (glm::abs(distance) > 0.0f && glm::distance2(distance * direction, localCenter) < radiusSquared));
}

bool AABox::parabolaPlaneIntersectsBoundingSphere(const glm::vec3& origin, const glm::vec3& velocity, const glm::vec3& acceleration, const glm::vec3& normal) const {
    glm::vec3 localCenter = calcCenter() - origin;
    const float ONE_OVER_TWO_SQUARED = 0.25f;
    float radiusSquared = ONE_OVER_TWO_SQUARED * glm::length2(_scale);

    // origin is inside the sphere
    if (glm::length2(localCenter) < radiusSquared) {
        return true;
    }

    if (glm::length2(acceleration) < EPSILON) {
        // Handle the degenerate case where acceleration == (0, 0, 0)
        return rayHitsBoundingSphere(origin, glm::normalize(velocity));
    } else {
        // Project vector from plane to sphere center onto the normal
        float distance = glm::dot(localCenter, normal);
        if (distance * distance < radiusSquared) {
            return true;
        }
    }
    return false;
}

bool AABox::touchesSphere(const glm::vec3& center, float radius) const {
    // Avro's algorithm from this paper: http://www.mrtc.mdh.se/projects/3Dgraphics/paperF.pdf
    glm::vec3 e = glm::max(_corner - center, Vectors::ZERO) + glm::max(center - _corner - _scale, Vectors::ZERO);
    return glm::length2(e) <= radius * radius;
}

bool AABox::findSpherePenetration(const glm::vec3& center, float radius, glm::vec3& penetration) const {
    glm::vec4 center4 = glm::vec4(center, 1.0f);

    float minPenetrationLength = FLT_MAX;
    for (int i = 0; i < FACE_COUNT; i++) {
        glm::vec4 facePlane = getPlane((BoxFace)i);
        glm::vec3 vector = getClosestPointOnFace(center, (BoxFace)i) - center;
        if (glm::dot(center4, getPlane((BoxFace)i)) >= 0.0f) {
            // outside this face, so use vector to closest point to determine penetration
            return ::findSpherePenetration(vector, glm::vec3(-facePlane), radius, penetration);
        }
        float vectorLength = glm::length(vector);
        if (vectorLength < minPenetrationLength) {
            // remember the smallest penetration vector; if we're inside all faces, we'll use that
            penetration = (vectorLength < EPSILON) ? glm::vec3(-facePlane) * radius :
                vector * ((vectorLength + radius) / -vectorLength);
            minPenetrationLength = vectorLength;
        }
    }

    return true;
}

bool AABox::findCapsulePenetration(const glm::vec3& start, const glm::vec3& end, float radius, glm::vec3& penetration) const {
    glm::vec4 start4 = glm::vec4(start, 1.0f);
    glm::vec4 end4 = glm::vec4(end, 1.0f);
    glm::vec4 startToEnd = glm::vec4(end - start, 0.0f);

    float minPenetrationLength = FLT_MAX;
    for (int i = 0; i < FACE_COUNT; i++) {
        // find the vector from the segment to the closest point on the face (starting from deeper end)
        glm::vec4 facePlane = getPlane((BoxFace)i);
        glm::vec3 closest = (glm::dot(start4, facePlane) <= glm::dot(end4, facePlane)) ?
            getClosestPointOnFace(start4, startToEnd, (BoxFace)i) : getClosestPointOnFace(end4, -startToEnd, (BoxFace)i);
        glm::vec3 vector = -computeVectorFromPointToSegment(closest, start, end);
        if (glm::dot(vector, glm::vec3(facePlane)) < 0.0f) {
            // outside this face, so use vector to closest point to determine penetration
            return ::findSpherePenetration(vector, glm::vec3(-facePlane), radius, penetration);
        }
        float vectorLength = glm::length(vector);
        if (vectorLength < minPenetrationLength) {
            // remember the smallest penetration vector; if we're inside all faces, we'll use that
            penetration = (vectorLength < EPSILON) ? glm::vec3(-facePlane) * radius :
                vector * ((vectorLength + radius) / -vectorLength);
            minPenetrationLength = vectorLength;
        }
    }

    return true;
}

glm::vec3 AABox::getClosestPointOnFace(const glm::vec3& point, BoxFace face) const {
    switch (face) {
        case MIN_X_FACE:
            return glm::clamp(point, glm::vec3(_corner.x, _corner.y, _corner.z),
                glm::vec3(_corner.x, _corner.y + _scale.y, _corner.z + _scale.z));

        case MAX_X_FACE:
            return glm::clamp(point, glm::vec3(_corner.x + _scale.x, _corner.y, _corner.z),
                glm::vec3(_corner.x + _scale.x, _corner.y + _scale.y, _corner.z + _scale.z));

        case MIN_Y_FACE:
            return glm::clamp(point, glm::vec3(_corner.x, _corner.y, _corner.z),
                glm::vec3(_corner.x + _scale.x, _corner.y, _corner.z + _scale.z));

        case MAX_Y_FACE:
            return glm::clamp(point, glm::vec3(_corner.x, _corner.y + _scale.y, _corner.z),
                glm::vec3(_corner.x + _scale.x, _corner.y + _scale.y, _corner.z + _scale.z));

        case MIN_Z_FACE:
            return glm::clamp(point, glm::vec3(_corner.x, _corner.y, _corner.z),
                glm::vec3(_corner.x + _scale.x, _corner.y + _scale.y, _corner.z));

        default: //quiet windows warnings
        case MAX_Z_FACE:
            return glm::clamp(point, glm::vec3(_corner.x, _corner.y, _corner.z + _scale.z),
                glm::vec3(_corner.x + _scale.x, _corner.y + _scale.y, _corner.z + _scale.z));
    }
}

glm::vec3 AABox::getClosestPointOnFace(const glm::vec4& origin, const glm::vec4& direction, BoxFace face) const {
    // check against the four planes that border the face
    BoxFace oppositeFace = getOppositeFace(face);
    bool anyOutside = false;
    for (int i = 0; i < FACE_COUNT; i++) {
        if (i == face || i == oppositeFace) {
            continue;
        }
        glm::vec4 iPlane = getPlane((BoxFace)i);
        float originDistance = glm::dot(origin, iPlane);
        if (originDistance < 0.0f) {
            continue; // inside the border
        }
        anyOutside = true;
        float divisor = glm::dot(direction, iPlane);
        if (fabsf(divisor) < EPSILON) {
            continue; // segment is parallel to plane
        }
        // find intersection and see if it lies within face bounds
        float directionalDistance = -originDistance / divisor;
        glm::vec4 intersection = origin + direction * directionalDistance;
        BoxFace iOppositeFace = getOppositeFace((BoxFace)i);
        for (int j = 0; j < FACE_COUNT; j++) {
            if (j == face || j == oppositeFace || j == i || j == iOppositeFace) {
                continue;
            }
            if (glm::dot(intersection, getPlane((BoxFace)j)) > 0.0f) {
                goto outerContinue; // intersection is out of bounds
            }
        }
        return getClosestPointOnFace(glm::vec3(intersection), face);

        outerContinue: ;
    }

    // if we were outside any of the sides, we must check against the diagonals
    if (anyOutside) {
        int faceAxis = face / 2;
        int secondAxis = (faceAxis + 1) % 3;
        int thirdAxis = (faceAxis + 2) % 3;

        glm::vec4 secondAxisMinPlane = getPlane((BoxFace)(secondAxis * 2));
        glm::vec4 secondAxisMaxPlane = getPlane((BoxFace)(secondAxis * 2 + 1));
        glm::vec4 thirdAxisMaxPlane = getPlane((BoxFace)(thirdAxis * 2 + 1));

        glm::vec4 offset = glm::vec4(0.0f, 0.0f, 0.0f,
            glm::dot(glm::vec3(secondAxisMaxPlane + thirdAxisMaxPlane), _scale) * 0.5f);
        glm::vec4 diagonals[] = { secondAxisMinPlane + thirdAxisMaxPlane + offset,
            secondAxisMaxPlane + thirdAxisMaxPlane + offset };

        float minDistance = FLT_MAX;
        for (size_t i = 0; i < sizeof(diagonals) / sizeof(diagonals[0]); i++) {
            float divisor = glm::dot(direction, diagonals[i]);
            if (fabsf(divisor) < EPSILON) {
                continue; // segment is parallel to diagonal plane
            }
            minDistance = glm::min(-glm::dot(origin, diagonals[i]) / divisor, minDistance);
        }
        if (minDistance != FLT_MAX) {
            return getClosestPointOnFace(glm::vec3(origin + direction * minDistance), face);
        }
    }

    // last resort or all inside: clamp origin to face
    return getClosestPointOnFace(glm::vec3(origin), face);
}

bool AABox::touchesAAEllipsoid(const glm::vec3& center, const glm::vec3& radials) const {
    // handle case where ellipsoid's alix-aligned box doesn't touch this AABox
    if (_corner.x - radials.x > center.x ||
        _corner.y - radials.y > center.y ||
        _corner.z - radials.z > center.z ||
        _corner.x + _scale.x + radials.x < center.x ||
        _corner.y + _scale.y + radials.y < center.y ||
        _corner.z + _scale.z + radials.z < center.z) {
        return false;
    }

    // handle case where ellipsoid is entirely inside this AABox
    if (contains(center)) {
        return true;
    }

    for (int i = 0; i < FACE_COUNT; i++) {
        glm::vec3 closest = getClosestPointOnFace(center, (BoxFace)i) - center;
        float x = closest.x;
        float y = closest.y;
        float z = closest.z;
        float a = radials.x;
        float b = radials.y;
        float c = radials.z;
        if (x*x/(a*a) + y*y/(b*b) + z*z/(c*c) < 1.0f) {
            return true;
        }
    }
    return false;
}


glm::vec4 AABox::getPlane(BoxFace face) const {
    switch (face) {
        case MIN_X_FACE: return glm::vec4(-1.0f, 0.0f, 0.0f, _corner.x);
        case MAX_X_FACE: return glm::vec4(1.0f, 0.0f, 0.0f, -_corner.x - _scale.x);
        case MIN_Y_FACE: return glm::vec4(0.0f, -1.0f, 0.0f, _corner.y);
        case MAX_Y_FACE: return glm::vec4(0.0f, 1.0f, 0.0f, -_corner.y - _scale.y);
        case MIN_Z_FACE: return glm::vec4(0.0f, 0.0f, -1.0f, _corner.z);
        default: //quiet windows warnings
        case MAX_Z_FACE: return glm::vec4(0.0f, 0.0f, 1.0f, -_corner.z - _scale.z);
    }
}

BoxFace AABox::getOppositeFace(BoxFace face) {
    switch (face) {
        case MIN_X_FACE: return MAX_X_FACE;
        case MAX_X_FACE: return MIN_X_FACE;
        case MIN_Y_FACE: return MAX_Y_FACE;
        case MAX_Y_FACE: return MIN_Y_FACE;
        case MIN_Z_FACE: return MAX_Z_FACE;
        default: //quiet windows warnings
        case MAX_Z_FACE: return MIN_Z_FACE;
    }
}

AABox AABox::clamp(const glm::vec3& min, const glm::vec3& max) const {
    glm::vec3 clampedCorner = glm::clamp(_corner, min, max);
    glm::vec3 clampedTopFarLeft = glm::clamp(calcTopFarLeft(), min, max);
    glm::vec3 clampedScale = clampedTopFarLeft - clampedCorner;

    return AABox(clampedCorner, clampedScale);
}

AABox AABox::clamp(float min, float max) const {
    glm::vec3 clampedCorner = glm::clamp(_corner, min, max);
    glm::vec3 clampedTopFarLeft = glm::clamp(calcTopFarLeft(), min, max);
    glm::vec3 clampedScale = clampedTopFarLeft - clampedCorner;

    return AABox(clampedCorner, clampedScale);
}

void AABox::embiggen(float scale) {
    _corner += scale * (-0.5f * _scale);
    _scale *= scale;
}

void AABox::embiggen(const glm::vec3& scale) {
    _corner += scale * (-0.5f * _scale);
    _scale *= scale;
}

void AABox::setScaleStayCentered(const glm::vec3& scale) {
    _corner += -0.5f * scale;
    _scale = scale;
}

void AABox::scale(float scale) {
    _corner *= scale;
    _scale *= scale;
}

void AABox::scale(const glm::vec3& scale) {
    _corner *= scale;
    _scale *= scale;
}

void AABox::rotate(const glm::quat& rotation) {
    auto minimum = _corner;
    auto maximum = _corner + _scale;

    glm::vec3 bottomLeftNear(minimum.x, minimum.y, minimum.z);
    glm::vec3 bottomRightNear(maximum.x, minimum.y, minimum.z);
    glm::vec3 bottomLeftFar(minimum.x, minimum.y, maximum.z);
    glm::vec3 bottomRightFar(maximum.x, minimum.y, maximum.z);
    glm::vec3 topLeftNear(minimum.x, maximum.y, minimum.z);
    glm::vec3 topRightNear(maximum.x, maximum.y, minimum.z);
    glm::vec3 topLeftFar(minimum.x, maximum.y, maximum.z);
    glm::vec3 topRightFar(maximum.x, maximum.y, maximum.z);

    glm::vec3 bottomLeftNearRotated = rotation * bottomLeftNear;
    glm::vec3 bottomRightNearRotated = rotation * bottomRightNear;
    glm::vec3 bottomLeftFarRotated = rotation * bottomLeftFar;
    glm::vec3 bottomRightFarRotated = rotation * bottomRightFar;
    glm::vec3 topLeftNearRotated = rotation * topLeftNear;
    glm::vec3 topRightNearRotated = rotation * topRightNear;
    glm::vec3 topLeftFarRotated = rotation * topLeftFar;
    glm::vec3 topRightFarRotated = rotation * topRightFar;

    minimum = glm::min(bottomLeftNearRotated,
        glm::min(bottomRightNearRotated,
        glm::min(bottomLeftFarRotated,
        glm::min(bottomRightFarRotated,
        glm::min(topLeftNearRotated,
        glm::min(topRightNearRotated,
        glm::min(topLeftFarRotated,
        topRightFarRotated)))))));

    maximum = glm::max(bottomLeftNearRotated,
        glm::max(bottomRightNearRotated,
        glm::max(bottomLeftFarRotated,
        glm::max(bottomRightFarRotated,
        glm::max(topLeftNearRotated,
        glm::max(topRightNearRotated,
        glm::max(topLeftFarRotated,
        topRightFarRotated)))))));

    _corner = minimum;
    _scale = maximum - minimum;
}

void AABox::transform(const Transform& transform) {
    scale(transform.getScale());
    rotate(transform.getRotation());
    translate(transform.getTranslation());
}

// Logic based on http://clb.demon.fi/MathGeoLib/nightly/docs/AABB.cpp_code.html#471
void AABox::transform(const glm::mat4& matrix) {
    // FIXME use simd operations
    auto halfSize = _scale * 0.5f;
    auto center = _corner + halfSize;
    halfSize = abs(halfSize);
    auto mm = glm::transpose(glm::mat3(matrix));
    vec3 newDir = vec3(
        glm::dot(glm::abs(mm[0]), halfSize),
        glm::dot(glm::abs(mm[1]), halfSize),
        glm::dot(glm::abs(mm[2]), halfSize)
    );

    auto newCenter = transformPoint(matrix, center);
    _corner = newCenter - newDir;
    _scale = newDir * 2.0f;
}

AABox AABox::getOctreeChild(OctreeChild child) const {
    AABox result(*this); // self
    switch (child) {
        case topLeftNear:
            result._corner.y += _scale.y / 2.0f;
            break;
        case topLeftFar:
            result._corner.y += _scale.y / 2.0f;
            result._corner.z += _scale.z / 2.0f;
            break;
        case topRightNear:
            result._corner.y += _scale.y / 2.0f;
            result._corner.x += _scale.x / 2.0f;
            break;
        case topRightFar:
            result._corner.y += _scale.y / 2.0f;
            result._corner.x += _scale.x / 2.0f;
            result._corner.z += _scale.z / 2.0f;
            break;
        case bottomLeftNear:
            // _corner = same as parent
            break;
        case bottomLeftFar:
            result._corner.z += _scale.z / 2.0f;
            break;
        case bottomRightNear:
            result._corner.x += _scale.x / 2.0f;
            break;
        case bottomRightFar:
            result._corner.x += _scale.x / 2.0f;
            result._corner.z += _scale.z / 2.0f;
            break;
    }
    result._scale /= 2.0f; // everything is half the scale
    return result;
}