// A hexagonal trivet with a honeycomb of hexagon holes.

/* [Trivet] */
// Width across the corners
size = 180; // [100:5:300]
// Hole size, corner to corner
cell = 16; // [8:1:40]
// Wall between holes
wall = 3; // [2:0.5:8]
// Solid border
border = 10; // [5:1:30]
// Corner rounding
round = 8; // [0:1:20]

/* [Hidden] */
R = size / 2;
r = cell / 2;
dx = 1.5 * r + wall * sqrt(3) / 2;
dy = sqrt(3) * r + wall;
n = ceil(R / dx) + 1;
apothem = R * sqrt(3) / 2 - border;

// Distance from the centre to p, measured across the flats of the outer hexagon.
function flat_distance(p) = max([for (k = [0:2]) abs(p[0] * cos(k * 60) + p[1] * sin(k * 60))]);

difference() {
  offset(r = round) offset(delta = -round) rotate(30) regular_polygon(6, R);
  for (i = [-n:n], j = [-n:n]) {
    p = [i * dx, j * dy + (abs(i) % 2) * dy / 2];
    if (flat_distance(p) + r <= apothem) translate(p) regular_polygon(6, r);
  }
}