experimental/Intersection/TriangleUtilities.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "TriangleUtilities.h"

// http://www.blackpawn.com/texts/pointinpoly/default.html
bool pointInTriangle(const Triangle& triangle, const _Point& pt) {
// Compute vectors
    _Vector v0 = triangle[2] - triangle[0];
    _Vector v1 = triangle[1] - triangle[0];
    _Vector v2 = pt - triangle[0];

// Compute dot products
    double dot00 = v0.dot(v0);
    double dot01 = v0.dot(v1);
    double dot02 = v0.dot(v2);
    double dot11 = v1.dot(v1);
    double dot12 = v1.dot(v2);

// Compute barycentric coordinates
    double invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
    double u = (dot11 * dot02 - dot01 * dot12) * invDenom;
    double v = (dot00 * dot12 - dot01 * dot02) * invDenom;

// Check if point is in triangle
    return (u >= 0) && (v >= 0) && (u + v < 1);
}