80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
#include "polygon_generator.h"
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#include <cassert>
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#include <cmath>
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static double to_rad(double angle_in_deg) {
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static double PI_180 = M_PI / 180;
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return angle_in_deg * PI_180;
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}
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polygon poly_generate::rectangle(double width, double height, double mass) {
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assert(width > 0);
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assert(height > 0);
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static const double one_over_twelve = 1. / 12;
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return polygon{{0, 0},
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0,
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{{-width / 2, -height / 2},
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{-width / 2, height / 2},
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{width / 2, height / 2},
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{width / 2, -height / 2}},
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one_over_twelve * mass * (width * width + height * height),
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mass};
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}
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polygon poly_generate::triangle(
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double side1, double side2, double angle, double mass) {
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assert(side1 > 0);
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assert(side2 > 0);
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static const double one_over_36 = 1. / 36;
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double base, height;
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base = side1;
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height = side2 * std::sin(to_rad(angle));
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vec2d points[] = {
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{0, 0}, {side1, 0}, {side2 * std::cos(to_rad(angle)), height}};
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vec2d barycenter = {
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(points[0].x + points[1].x + points[2].x) / 3,
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(points[0].y + points[1].y + points[2].y) / 3,
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};
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for (unsigned int i = 0; i < 3; ++i)
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points[i] -= barycenter;
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return polygon{{0, 0},
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0,
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{std::begin(points), std::end(points)},
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one_over_36 * mass * base * std::pow(height, 3),
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mass};
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}
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polygon poly_generate::regular(double radius, uint n_sides, double mass) {
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assert(n_sides > 2);
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std::vector<vec2d> points;
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points.reserve(n_sides);
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double theta = 2 * M_PI / n_sides;
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for (uint i = 0; i < n_sides; i++)
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points.push_back({radius * cos(i * theta), radius * sin(i * theta)});
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double l = vec2d::norm(points[1] - points[0]);
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double sin_, cos_;
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sincos(M_PI / n_sides, &sin_, &cos_);
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double cot = cos_ / sin_;
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double inertia = mass * l * l / 24 * (1 + 3 * cot * cot);
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return polygon{{0, 0}, 0, points, inertia, mass};
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}
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static double intertia_of_polygon_subtriangle(
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vec2d& centroid, vec2d& p1, vec2d& p2) {
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double base, height;
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if (vec2d::norm(p1 - centroid) > vec2d::norm(p2 - centroid))
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base = vec2d::norm(p1 - centroid);
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}
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polygon poly_generate::general(std::vector<vec2d>& points, double mass) {
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double intertia = 0;
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return polygon{{0, 0}, 0, points, intertia, mass};
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}
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