hex.cpp

#include <stdio.h>
#include <vector>

struct pt
{
    double x;
    double y;
    pt(double a=0,double b=0) : x(a), y(b) {}
    void mul(double s) {
        x *= s;
        y *= s;
    }
};

pt lerp(const pt& a, const pt& b, double k) {
    pt res;
    res.x = a.x * (1.0-k) + k * b.x;
    res.y = a.y * (1.0-k) + k * b.y;
    return res;
}

#define SQ3 1.73205080757       // sqrt(3)
#define SQ3d2 0.86602540378     // sqrt(3)/2

pt hex[6];

int main()
{
    // options
    double max_ring_radius = 1.0;
    int n_rings = 6;
    double tilt_angle = 0.0;

    // -------------------------------------------------------------------------

    hex[0] = pt(1.0, 0.0);
    hex[1] = pt(0.5, SQ3d2);
    hex[2] = pt(-0.5, SQ3d2);
    hex[3] = pt(-1.0, 0.0);
    hex[4] = pt(-0.5, -SQ3d2);
    hex[5] = pt(0.5, -SQ3d2);

    // rotate
    {
        double ca = cos(tilt_angle);
        double sa = cos(tilt_angle);
        for (int i=0; i<6; i++) {
            double x = hex[i].x;
            double y = hex[i].y;
            hex[i].x = x*ca - y*sa;
            hex[i].y = x*sa + y*ca;
        }
    }

    // result
    std::vector<pt> pts;

    // magic
    // (for each ring, for each edge, get edge's endpoints and gen samples on lerped points)
    pts.push_back(pt(0.0,0.0));
    for (int i=1; i<=n_rings; i++) {
        double ring_radius = max_ring_radius * (double)i/(double)n_rings;
        for (int e=0; e<6; e++) {
            pt a = hex[e];
            pt b = hex[(e+1)%6];
            for (int d=0; d<i; d++) {
                pt p = lerp(a,b,(double)d/(double)i);
                p.mul(ring_radius);
                pts.push_back(p);
            }
        }
    }

    // print
    printf("%d\n" , pts.size());
    for (size_t i=0; i<pts.size(); i++)
        printf("float2(%2.6f, %2.6f),\n", pts[i].x, pts[i].y);

    return 0;
}