particle component

scripts/geometry.js

@@ -0,0 +1,26 @@
+var Sphere = {};
+Sphere.volume = function(r) { return Math.pi*r*r*r*4/3; };
+Sphere.random = function(r,theta,phi)
+{
+  if (typeof r === 'number') r = [r,r];
+  theta ??= [0,1];
+  phi ??= [-0.5,0.5];
+  if (typeof theta === 'number') theta = [theta,theta];
+  if (typeof phi === 'number') phi = [phi,phi];
+  
+  var ra = Math.random_range(r[0],r[1]);
+  var ta = Math.turn2rad(Math.random_range(theta[0],theta[1]));
+  var pa = Math.turn2rad(Math.random_range(phi[0],phi[1]));
+  return [
+    ra*Math.sin(ta)*Math.cos(pa),
+    ra*Math.sin(ta)*Math.sin(pa),
+    ra*Math.cos(ta)
+  ];
+}
+
+var Circle = {};
+Circle.area = function(r) { return Math.pi*r*r; };
+Circle.random = function(r,theta)
+{
+  return Sphere.random(r,theta).xz;
+}