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C++

#include "FITKCircleAlg.h"
#include "FITKVec3DAlg.h"
#include <cmath>
namespace Core
{
QPair<FITKPoint, FITKPoint> GetCircleCenter(const FITKPoint& p1, const FITKPoint& p2,
const FITKPoint& another, const double r)
{
QPair<FITKPoint, FITKPoint> centers;
//弦 P1 P2中点
const FITKPoint mid((p1.x() + p2.x()) / 2, (p1.y() + p2.y()) / 2, (p1.z() + p2.z()) / 2);
//弦长度的一半,与半径可形成直角三角形
const double d = Distance(p1, mid);
if (d > r) return centers;
//直角三角形的另一边长度
const double offset = sqrt(r*r - d * d);
const FITKVec3D m2(p2, mid);
const FITKVec3D mo(another, mid);
const FITKVec3D mz = CrossProduct(m2, mo);
//半径方向
FITKVec3D dir = CrossProduct(m2, mz);
dir.normalize();
//弦中心点向两侧偏移分别得到两个圆心位置
centers.first = FITKPoint(mid.x() + dir.x()* offset,
mid.y() + dir.y()* offset,
mid.z() + dir.z()* offset);
centers.second = FITKPoint(mid.x() - dir.x()* offset,
mid.y() - dir.y()* offset,
mid.z() - dir.z()* offset);
return centers;
}
FITKPoint GetMidPointOnArc(const FITKPoint& p1, const FITKPoint& p2, const FITKPoint& center, const double r)
{
//弦 P1 P2中点
const FITKPoint mid((p1.x() + p2.x()) / 2, (p1.y() + p2.y()) / 2, (p1.z() + p2.z()) / 2);
const double d = Distance(p1, mid);
if (d >= r) return FITKPoint();
//圆心到弦中点的方向
FITKVec3D dir(mid,center);
dir.normalize();
//圆心偏移
return Add(center, dir, 1, r);
}
void GetCircleBy3Points(const FITKPoint& p1, const FITKPoint& p2, const FITKPoint& p3,
FITKPoint& center, FITKVec3D& normal, double& r)
{
//计算圆心
double a1 = (p1.y()*p2.z() - p2.y() * p1.z() - p1.y() * p3.z() + p3.y() * p1.z() + p2.y() * p3.z() - p3.y() * p2.z()),
b1 = -(p1.x()*p2.z() - p2.x() * p1.z() - p1.x() * p3.z() + p3.x() * p1.z() + p2.x() * p3.z() - p3.x() * p2.z()),
c1 = (p1.x()*p2.y() - p2.x() * p1.y() - p1.x() * p3.y() + p3.x() * p1.y() + p2.x() * p3.y() - p3.x() * p2.y()),
d1 = -(p1.x()*p2.y()*p3.z() - p1.x() * p3.y()*p2.z() - p2.x() * p1.y()*p3.z() + p2.x() * p3.y()*p1.z() + p3.x() * p1.y()*p2.z() - p3.x() * p2.y()*p1.z());
double a2 = 2 * (p2.x() - p1.x()),
b2 = 2 * (p2.y() - p1.y()),
c2 = 2 * (p2.z() - p1.z()),
d2 = p1.x() * p1.x() + p1.y() * p1.y() + p1.z() * p1.z() - p2.x() * p2.x() - p2.y() * p2.y() - p2.z() * p2.z();
double a3 = 2 * (p3.x() - p1.x()),
b3 = 2 * (p3.y() - p1.y()),
c3 = 2 * (p3.z() - p1.z()),
d3 = p1.x() * p1.x() + p1.y() * p1.y() + p1.z() * p1.z() - p3.x() * p3.x() - p3.y() * p3.y() - p3.z() * p3.z();
double x = -(b1*c2*d3 - b1 * c3*d2 - b2 * c1*d3 + b2 * c3*d1 + b3 * c1*d2 - b3 * c2*d1)
/ (a1*b2*c3 - a1 * b3*c2 - a2 * b1*c3 + a2 * b3*c1 + a3 * b1*c2 - a3 * b2*c1);
double y = (a1*c2*d3 - a1 * c3*d2 - a2 * c1*d3 + a2 * c3*d1 + a3 * c1*d2 - a3 * c2*d1)
/ (a1*b2*c3 - a1 * b3*c2 - a2 * b1*c3 + a2 * b3*c1 + a3 * b1*c2 - a3 * b2*c1);
double z = -(a1*b2*d3 - a1 * b3*d2 - a2 * b1*d3 + a2 * b3*d1 + a3 * b1*d2 - a3 * b2*d1)
/ (a1*b2*c3 - a1 * b3*c2 - a2 * b1*c3 + a2 * b3*c1 + a3 * b1*c2 - a3 * b2*c1);
//计算半径
r = sqrt((p1.x() - x)*(p1.x() - x) + (p1.y() - y)*(p1.y() - y) + (p1.z() - z)*(p1.z() - z));
//返回圆心
center = FITKPoint(x, y, z);
//计算三个点法向
const FITKVec3D v1(p1, p2);
const FITKVec3D v2(p1, p3);
normal = CrossProduct(v1, v2);
normal.normalize();
}
}