Added all remaining gists.

samplings.m/README.md

@@ -0,0 +1 @@
+Based on explanations from scrathapixel.com, stackoverflow.com and Wolfram Mathworld.

samplings.m/samplings.m

@@ -0,0 +1,46 @@
+function [nt, nb] = coord_system(n)
+  if abs(n(1)) > abs(n(2))
+    nt = [n(3), 0, -n(1)] / norm([n(3), 0, -n(1)]);
+  else
+    nt = [0, -n(3), n(2)] / norm([0, -n(3), n(2)]);
+  endif
+  v = cross(n, nt);
+  nb = v / norm(v);
+endfunction
+
+function [x, y, z] = disk_sampling(c, n, r)
+  rr = rand() * r;
+  [nt, nb] = coord_system(n);
+
+  theta = rand() * 2 * pi;
+  x = c(1) + (rr * cos(theta) * nt(1)) + (rr * sin(theta) * nb(1));
+  y = c(2) + (rr * cos(theta) * nt(2)) + (rr * sin(theta) * nb(2));
+  z = c(3) + (rr * cos(theta) * nt(3)) + (rr * sin(theta) * nb(3));
+endfunction
+
+function [x, y, z] = sphere_sampling(c, r)
+  theta = rand() * 2 * pi;
+  u = (rand() * 2) - 1;
+  sqrt1muu = sqrt(1 - (u * u));
+  x = (r * sqrt1muu * cos(theta)) + c(1);
+  y = (r * sqrt1muu * sin(theta)) + c(2);
+  z = (r * u) + c(3);
+endfunction
+
+function test_sampling()
+  x = [];
+  y = [];
+  z = [];
+  for i = 1:5000
+   %[sx, sy, sz] = disk_sampling([0, 0.75, -1], [0, -1, 0], 0.15);
+    [sx, sy, sz] = sphere_sampling([0, 0.75, -1], 0.15);
+    x(end + 1) = sx;
+    y(end + 1) = sy;
+    z(end + 1) = sz;
+  endfor
+  scatter3(x, y, z);
+  axis([-2, 2, -2, 2, -2, 2]);
+  xlabel('x');
+  ylabel('y');
+  zlabel('z');
+endfunction