begin drawing faces

sketch.js

@@ -5,6 +5,10 @@ let sphere_radius = 200;
 let physics = false;
 let earth = false;
 let skeleton = false;
+let planes = false;
+
+let red;
+let yellow;
 
 function preload() {
   earth_image = loadImage("atlas1.jpg");
@@ -12,6 +16,8 @@ function preload() {
 
 function setup() {
   createCanvas(600, 600, WEBGL);
+  red = color(0xbf, 0x00, 0x00);
+  yellow = color(0xff, 0xff, 0x00);
 }
 
 function draw() {
@@ -25,6 +31,41 @@ function draw() {
   if (skeleton) {
     draw_skeleton(sphere_radius);
   }
+
+  if (planes) {
+    let p = charges[0];
+    let a = charges[1];
+    let b = charges[2];
+    p.color = yellow;
+    a.color = yellow;
+    b.color = yellow;
+    let n = p5.Vector.sub(p.position, a.position).cross(p5.Vector.sub(p.position, b.position));
+    n.normalize(); // unnecessary
+    push();
+    strokeWeight(5);
+    stroke(0x7f);
+    line(
+      0,0,0,
+      n.x*sphere_radius,n.y*sphere_radius,n.z*sphere_radius,
+    )
+    fill(0xff);
+    strokeWeight(3);
+    stroke(0x00);
+    beginShape(TRIANGLES);
+    const v1 = p5.Vector.mult(p.position, sphere_radius);
+    const v2 = p5.Vector.mult(a.position, sphere_radius);
+    const v3 = p5.Vector.mult(b.position, sphere_radius);
+    vertex(v1.x, v1.y, v1.z);
+    vertex(v2.x, v2.y, v2.z);
+    vertex(v3.x, v3.y, v3.z);
+    endShape();
+    pop();
+  } else {
+    for (let charge of charges) {
+      charge.color = red;
+    }
+  }
+
   draw_charges(sphere_radius);
   draw_sphere(sphere_radius, 25);
 }
@@ -67,6 +108,7 @@ function make_charges(n) {
       position: position,
       velocity: createVector(),
       acceleration: createVector(),
+      color: red,
     });
   }
 }
@@ -74,8 +116,8 @@ function make_charges(n) {
 function draw_charges(radius) {
   push();
   noStroke();
-  ambientMaterial(0xbf, 0x00, 0x00);
   for (let charge of charges.values()) {
+    ambientMaterial(charge.color);
     let position = charge.position.copy();
     position.mult(radius);
     push();
@@ -156,7 +198,13 @@ function keyPressed() {
     earth = !earth;
   } else if (key == 'f') {
     skeleton = !skeleton;
+  } else if (key == 'g') {
+    planes = !planes;
   } else if (key >= '0' && key <= '9') {
     make_charges(int(key));
   }
 }
+
+// TODO draw faces
+// algorithm: choose 3 vertices until 2-partition of other vertices has one empty set
+// done when V - E + F = 2. V is known. count E and F while creating faces