aabb.cpp

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/*
Copyright (C) 2002-2020 UFO: Alien Invasion.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

#include "aabb.h"
#include "mathlib.h"

AABB::AABB ()
{
    VectorCopy(vec3_origin, mins);
    VectorCopy(vec3_origin, maxs);
}
AABB::AABB (const vec3_t mini, const vec3_t maxi)
{
    VectorCopy(mini, mins);
    VectorCopy(maxi, maxs);
}
AABB::AABB (const vec_t minX, const vec_t minY, const vec_t minZ, const vec_t maxX, const vec_t maxY, const vec_t maxZ)
{
    mins[0] = minX;
    mins[1] = minY;
    mins[2] = minZ;
    maxs[0] = maxX;
    maxs[1] = maxY;
    maxs[2] = maxZ;
}
AABB::AABB (const Line& line)
{
    VectorSet(mins, std::min(line.start[0], line.stop[0]), std::min(line.start[1], line.stop[1]), std::min(line.start[2], line.stop[2]));
    VectorSet(maxs, std::max(line.start[0], line.stop[0]), std::max(line.start[1], line.stop[1]), std::max(line.start[2], line.stop[2]));
}

void AABB::add (const vec3_t point)
{
    for (int i = 0; i < 3; i++) {
        const vec_t val = point[i];
        if (val < mins[i])
            mins[i] = val;
        if (val > maxs[i])
            maxs[i] = val;
    }
}
void AABB::add (const AABB& other)
{
    for (int i = 0; i < 3; i++) {
        if (other.mins[i] < mins[i])
            mins[i] = other.mins[i];
        if (other.maxs[i] > maxs[i])
            maxs[i] = other.maxs[i];
    }
}

void AABB::rotateAround (const vec3_t origin, const vec3_t angles) {
    /* reject non-rotations */
    if (VectorEmpty(angles))
        return;

    /* construct box-centered coordinates (center and corners) */
    vec3_t center, halfDiagonal;

    VectorInterpolation(mins, maxs, 0.5f, center);
    VectorSubtract(maxs, center, halfDiagonal);

    /* offset coordinate frame to rotation origin */
    VectorSubtract(center, origin, center);

    /* rotate center by given angles */
    vec3_t m[3];
    VectorCreateRotationMatrix(angles, m);

    vec3_t newCenter;
    VectorRotate(m, center, newCenter);

    /* short-circuit calculation of the rotated box half-extents */
    /* shortcut is: instead of calculating all 8 AABB corners, use the symmetry by rotating box around it's center. */
    VectorAbs(m[0]);
    VectorAbs(m[1]);
    VectorAbs(m[2]);

    vec3_t newHalfDiagonal;
    VectorRotate(m, halfDiagonal, newHalfDiagonal);

    /* de-offset coordinate frame from rotation origin */
    VectorAdd(newCenter, origin, newCenter);

    /* finally, combine results into new AABB */
    VectorAdd(newCenter, newHalfDiagonal, maxs);
    VectorSubtract(newCenter, newHalfDiagonal, mins);
}

const AABB AABB::EMPTY;