dep/src/g3dlite/Triangle.cpp

   1 /**
   2  @file Triangle.cpp
   3
   4  @maintainer Morgan McGuire, graphics3d.com
   5
   6  @created 2001-04-06
   7  @edited  2006-01-20
   8
   9  Copyright 2000-2006, Morgan McGuire.
  10  All rights reserved.
  11  */
  12
  13 #include "G3D/platform.h"
  14 #include "G3D/Triangle.h"
  15 #include "G3D/Plane.h"
  16 #include "G3D/AABox.h"
  17
  18 namespace G3D {
  19
  20
  21 void Triangle::init(const Vector3& v0, const Vector3& v1, const Vector3& v2) {
  22
  23     _plane = Plane(v0, v1, v2);
  24     _vertex[0] = v0;
  25     _vertex[1] = v1;
  26     _vertex[2] = v2;
  27
  28     static int next[] = {1,2,0};
  29
  30     for (int i = 0; i < 3; ++i) {
  31         const Vector3 e  = _vertex[next[i]] - _vertex[i];
  32         edgeMagnitude[i]    = e.magnitude();
  33
  34         if (edgeMagnitude[i] == 0) {
  35             edgeDirection[i] = Vector3::zero();
  36         } else {
  37             edgeDirection[i] = e / (float)edgeMagnitude[i];
  38         }
  39     }
  40
  41     edge01 = _vertex[1] - _vertex[0];
  42     edge02 = _vertex[2] - _vertex[0];
  43
  44     _primaryAxis = _plane.normal().primaryAxis();
  45     _area = (float)edgeDirection[0].cross(edgeDirection[2]).magnitude() * (edgeMagnitude[0] * edgeMagnitude[2]);
  46
  47 }
  48
  49
  50 Triangle::Triangle() {
  51     init(Vector3::zero(), Vector3::zero(), Vector3::zero());
  52 }
  53
  54
  55 Triangle::Triangle(const Vector3& v0, const Vector3& v1, const Vector3& v2) {
  56     init(v0, v1, v2);
  57 }
  58
  59
  60 Triangle::~Triangle() {
  61 }
  62
  63
  64 double Triangle::area() const {
  65     return _area;
  66 }
  67
  68
  69 const Vector3& Triangle::normal() const {
  70     return _plane.normal();
  71 }
  72
  73
  74 const Plane& Triangle::plane() const {
  75     return _plane;
  76 }
  77
  78
  79 Vector3 Triangle::center() const {
  80     return (_vertex[0] + _vertex[1] + _vertex[2]) / 3.0;
  81 }
  82
  83 Vector3 Triangle::randomPoint() const {
  84     // Choose a random point in the parallelogram
  85
  86     float s = uniformRandom();
  87     float t = uniformRandom();
  88
  89     if (t > 1.0f - s) {
  90         // Outside the triangle; reflect about the
  91         // diagonal of the parallelogram
  92         t = 1.0f - t;
  93         s = 1.0f - s;
  94     }
  95
  96     return edge01 * s + edge02 * t + _vertex[0];
  97 }
  98
  99
 100 void Triangle::getBounds(AABox& out) const {
 101     Vector3 lo = _vertex[0];
 102     Vector3 hi = lo;
 103
 104     for (int i = 1; i < 3; ++i) {
 105         lo = lo.min(_vertex[i]);
 106         hi = hi.max(_vertex[i]);
 107     }
 108
 109     out = AABox(lo, hi);
 110 }
 111
 112 } // G3D