geometry.cpp

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/*
    pbrt source code Copyright(c) 1998-2010 Matt Pharr and Greg Humphreys.

    This file is part of pbrt.

    pbrt 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.  Note that the text contents of
    the book "Physically Based Rendering" are *not* licensed under the
    GNU GPL.

    pbrt 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, see <http://www.gnu.org/licenses/>.

 */


// core/geometry.cpp*
#include "stdafx.h"
#include "geometry.h"

// BBox Method Definitions
BBox Union(const BBox &b, const Point &p) {
    BBox ret = b;
    ret.pMin.x = min(b.pMin.x, p.x);
    ret.pMin.y = min(b.pMin.y, p.y);
    ret.pMin.z = min(b.pMin.z, p.z);
    ret.pMax.x = max(b.pMax.x, p.x);
    ret.pMax.y = max(b.pMax.y, p.y);
    ret.pMax.z = max(b.pMax.z, p.z);
    return ret;
}


BBox Union(const BBox &b, const BBox &b2) {
    BBox ret;
    ret.pMin.x = min(b.pMin.x, b2.pMin.x);
    ret.pMin.y = min(b.pMin.y, b2.pMin.y);
    ret.pMin.z = min(b.pMin.z, b2.pMin.z);
    ret.pMax.x = max(b.pMax.x, b2.pMax.x);
    ret.pMax.y = max(b.pMax.y, b2.pMax.y);
    ret.pMax.z = max(b.pMax.z, b2.pMax.z);
    return ret;
}


void BBox::BoundingSphere(Point *c, float *rad) const {
    *c = .5f * pMin + .5f * pMax;
    *rad = Inside(*c) ? Distance(*c, pMax) : 0.f;
}


bool BBox::IntersectP(const Ray &ray, float *hitt0,
                      float *hitt1) const {
    float t0 = ray.mint, t1 = ray.maxt;
    for (int i = 0; i < 3; ++i) {
        // Update interval for _i_th bounding box slab
        float invRayDir = 1.f / ray.d[i];
        float tNear = (pMin[i] - ray.o[i]) * invRayDir;
        float tFar  = (pMax[i] - ray.o[i]) * invRayDir;

        // Update parametric interval from slab intersection $t$s
        if (tNear > tFar) swap(tNear, tFar);
        t0 = tNear > t0 ? tNear : t0;
        t1 = tFar  < t1 ? tFar  : t1;
        if (t0 > t1) return false;
    }
    if (hitt0) *hitt0 = t0;
    if (hitt1) *hitt1 = t1;
    return true;
}

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