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/**
@file Triangle.cpp
@maintainer Morgan McGuire, http://graphics.cs.williams.edu
@created 2001-04-06
@edited 2008-12-28
Copyright 2000-2009, Morgan McGuire.
All rights reserved.
*/
#include "G3D/platform.h"
#include "G3D/Triangle.h"
#include "G3D/Plane.h"
#include "G3D/BinaryInput.h"
#include "G3D/BinaryOutput.h"
#include "G3D/debugAssert.h"
#include "G3D/AABox.h"
#include "G3D/Ray.h"
namespace G3D {
void Triangle::init(const Vector3& v0, const Vector3& v1, const Vector3& v2) {
_plane = Plane(v0, v1, v2);
_vertex[0] = v0;
_vertex[1] = v1;
_vertex[2] = v2;
static int next[] = {1,2,0};
for (int i = 0; i < 3; ++i) {
const Vector3& e = _vertex[next[i]] - _vertex[i];
edgeMagnitude[i] = e.magnitude();
if (edgeMagnitude[i] == 0) {
edgeDirection[i] = Vector3::zero();
} else {
edgeDirection[i] = e / (float)edgeMagnitude[i];
}
}
_edge01 = _vertex[1] - _vertex[0];
_edge02 = _vertex[2] - _vertex[0];
_primaryAxis = _plane.normal().primaryAxis();
_area = 0.5f * edgeDirection[0].cross(edgeDirection[2]).magnitude() * (edgeMagnitude[0] * edgeMagnitude[2]);
//0.5f * (_vertex[1] - _vertex[0]).cross(_vertex[2] - _vertex[0]).dot(_plane.normal());
}
Triangle::Triangle() {
init(Vector3::zero(), Vector3::zero(), Vector3::zero());
}
Triangle::Triangle(const Vector3& v0, const Vector3& v1, const Vector3& v2) {
init(v0, v1, v2);
}
Triangle::~Triangle() {
}
Triangle::Triangle(class BinaryInput& b) {
deserialize(b);
}
void Triangle::serialize(class BinaryOutput& b) {
_vertex[0].serialize(b);
_vertex[1].serialize(b);
_vertex[2].serialize(b);
}
void Triangle::deserialize(class BinaryInput& b) {
_vertex[0].deserialize(b);
_vertex[1].deserialize(b);
_vertex[2].deserialize(b);
init(_vertex[0], _vertex[1], _vertex[2]);
}
float Triangle::area() const {
return _area;
}
const Vector3& Triangle::normal() const {
return _plane.normal();
}
const Plane& Triangle::plane() const {
return _plane;
}
Vector3 Triangle::center() const {
return (_vertex[0] + _vertex[1] + _vertex[2]) / 3.0;
}
Vector3 Triangle::randomPoint() const {
// Choose a random point in the parallelogram
float s = uniformRandom();
float t = uniformRandom();
if (t > 1.0f - s) {
// Outside the triangle; reflect about the
// diagonal of the parallelogram
t = 1.0f - t;
s = 1.0f - s;
}
return _edge01 * s + _edge02 * t + _vertex[0];
}
void Triangle::getBounds(AABox& out) const {
Vector3 lo = _vertex[0];
Vector3 hi = lo;
for (int i = 1; i < 3; ++i) {
lo = lo.min(_vertex[i]);
hi = hi.max(_vertex[i]);
}
out = AABox(lo, hi);
}
bool Triangle::intersect(const Ray& ray, float& distance, float baryCoord[3]) const {
static const float EPS = 1e-5f;
// See RTR2 ch. 13.7 for the algorithm.
const Vector3& e1 = edge01();
const Vector3& e2 = edge02();
const Vector3 p(ray.direction().cross(e2));
const float a = e1.dot(p);
if (abs(a) < EPS) {
// Determinant is ill-conditioned; abort early
return false;
}
const float f = 1.0f / a;
const Vector3 s(ray.origin() - vertex(0));
const float u = f * s.dot(p);
if ((u < 0.0f) || (u > 1.0f)) {
// We hit the plane of the m_geometry, but outside the m_geometry
return false;
}
const Vector3 q(s.cross(e1));
const float v = f * ray.direction().dot(q);
if ((v < 0.0f) || ((u + v) > 1.0f)) {
// We hit the plane of the triangle, but outside the triangle
return false;
}
const float t = f * e2.dot(q);
if ((t > 0.0f) && (t < distance)) {
// This is a new hit, closer than the previous one
distance = t;
baryCoord[0] = 1.0 - u - v;
baryCoord[1] = u;
baryCoord[2] = v;
return true;
} else {
// This hit is after the previous hit, so ignore it
return false;
}
}
} // G3D
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