double Face::getArea() const {
Vec3f a = (*this)[0]->get();
Vec3f b = (*this)[1]->get();
Vec3f c = (*this)[2]->get();
Vec3f d = (*this)[3]->get();
return
AreaOfTriangle(DistanceBetweenTwoPoints(a,b),
DistanceBetweenTwoPoints(a,c),
DistanceBetweenTwoPoints(b,c)) +
AreaOfTriangle(DistanceBetweenTwoPoints(c,d),
DistanceBetweenTwoPoints(a,d),
DistanceBetweenTwoPoints(a,c));
}
float Face::getArea() const {
glm::vec3 a = (*this)[0]->get();
glm::vec3 b = (*this)[1]->get();
glm::vec3 c = (*this)[2]->get();
glm::vec3 d = (*this)[3]->get();
return
AreaOfTriangle(DistanceBetweenTwoPoints(a,b),
DistanceBetweenTwoPoints(a,c),
DistanceBetweenTwoPoints(b,c)) +
AreaOfTriangle(DistanceBetweenTwoPoints(c,d),
DistanceBetweenTwoPoints(a,d),
DistanceBetweenTwoPoints(a,c));
}
int main(){
int n;
double xa[MAX_NUMS]; //多边形各顶点x坐标
double ya[MAX_NUMS]; //多边形各顶点y坐标
double x[3]; //三角形各顶点x坐标
double y[3]; //三角形各顶点y坐标
double area = 0.0; //面积
int i, j;
//输入n及各顶点坐标
printf("Enter the sides number of polygon(3≤N≤%d):\n", MAX_NUMS);
scanf("%d", &n);
for (i = 0; i < n; i++){
printf("Enter the coordinates of vertex A(%d):\n", i + 1);
scanf("%lf%lf", &xa[i], &ya[i]);
}
x[0] = xa[0];
y[0] = ya[0];
for (i = 0; i < n - 2; i++){
for (j = 1; j < 3; j++){
x[j] = xa[i + j];
y[j] = ya[i + j];
}
area = area + AreaOfTriangle(x, y);
}
printf("The area of the polygon is %g", area);
}
bool Face::isConvex() const {
Vec3f a = (*this)[0]->get();
Vec3f b = (*this)[1]->get();
Vec3f c = (*this)[2]->get();
Vec3f d = (*this)[3]->get();
// no D
double t1 = AreaOfTriangle(DistanceBetweenTwoPoints(a,b),
DistanceBetweenTwoPoints(a,c),
DistanceBetweenTwoPoints(b,c));
// no B
double t2 = AreaOfTriangle(DistanceBetweenTwoPoints(a,c),
DistanceBetweenTwoPoints(a,d),
DistanceBetweenTwoPoints(c,d));
// no C
double t3 = AreaOfTriangle(DistanceBetweenTwoPoints(a,d),
DistanceBetweenTwoPoints(a,b),
DistanceBetweenTwoPoints(b,d));
// no A
double t4 = AreaOfTriangle(DistanceBetweenTwoPoints(c,d),
DistanceBetweenTwoPoints(b,d),
DistanceBetweenTwoPoints(b,c));
if (!fabs((t1+t2)-(t3+t4) < .001)){
std::cout << " t1: " << t1 << std::endl;
std::cout << " t2: " << t2 << std::endl;
std::cout << " t3: " << t3 << std::endl;
std::cout << " t4: " << t4 << std::endl;
}
//assert(fabs((t1+t2)-(t3+t4) < .001));
if (fabs((t1+t2)-(t3+t4) < .001)){
return true;
}
else{
return false;
}
}
bool isLinear(const Vec3f &p1, const Vec3f &p2, const Vec3f &p3){
double triangle_area = AreaOfTriangle(DistanceBetweenTwoPoints(p1,p2),
DistanceBetweenTwoPoints(p1, p3),
DistanceBetweenTwoPoints(p2,p3));
//Non-zero triangle area means that the points are not colinear
if(triangle_area > EPSILON){
return false;
}
return true;
}
double vtTin::GetArea2D()
{
double area = 0.0;
uint tris = NumTris();
for (uint i = 0; i < tris; i++)
{
const DPoint2 &p1 = m_vert[m_tri[i*3]];
const DPoint2 &p2 = m_vert[m_tri[i*3+1]];
const DPoint2 &p3 = m_vert[m_tri[i*3+2]];
area += AreaOfTriangle(p1, p2, p3);
}
return area;
}
// Get random point in poly
fPoint CWorldServer::RandInPoly( fPoint p[], int pcount )
{
int tnum = 0;
float tval = 0;
float totalarea = 0;
float* areas = new float[pcount-1];
for(int i=0; i<pcount-2; i++) {
totalarea += AreaOfTriangle(p[0], p[i+1], p[i+2]);
areas[i+1] = totalarea;
}
tval = rand() * totalarea / RAND_MAX;
for (tnum=1; tnum<pcount-1; tnum++) { if(tval<=areas[tnum]&&tval>areas[tnum-1]) break; }
return RandInTriangle(p[0], p[tnum], p[tnum+1]);
}
double vtTin::GetArea3D()
{
double area = 0.0;
uint tris = NumTris();
for (uint i = 0; i < tris; i++)
{
const int v0 = m_tri[i*3];
const int v1 = m_tri[i*3+1];
const int v2 = m_tri[i*3+2];
const DPoint2 &p1 = m_vert[v0];
const DPoint2 &p2 = m_vert[v1];
const DPoint2 &p3 = m_vert[v2];
DPoint3 dp1(p1.x, p1.y, m_z[v0]);
DPoint3 dp2(p2.x, p2.y, m_z[v1]);
DPoint3 dp3(p3.x, p3.y, m_z[v2]);
area += AreaOfTriangle(dp1, dp2, dp3);
}
return area;
}
