​

function rand_v4(line_min = 10, line_max = 100) {

  let p1 = createVector(0, 0, 0);

  let p2 = createVector(random(line_min,line_max), 0, 0)

  let p3 = createVector(random(p2.x), random(line_min, line_max), 0)

  let p4 = createVector(p3.x, random(p3.y), random(line_min, line_max))

  // let volume = p2.x * p3.y * p4.z / 6

  let centroid = createVector((p1.x+p2.x+p3.x+p4.x)/4, 

                              (p1.y+p2.y+p3.y+p4.y)/4,

                              (p1.z+p2.z+p3.z+p4.z)/4) 

  return [p1.sub(centroid), p2.sub(centroid), 

          p3.sub(centroid), p4.sub(centroid)]

}

​

​

function fnorm(p1, p2, p3) {

  let a = p5.Vector.sub(p2,p1)

  let b = p5.Vector.sub(p3,p2)

  let n = p5.Vector.cross(a, b)

  let s = (n.dot(p1) > 0 ? 1 : -1)

  return n.mult(s)

}

​

function drawFace(f) {

  beginShape()

  normal(f[3].x, f[3].y, f[3].z)

  vertex(f[0].x, f[0].y, f[0].z)

  vertex(f[1].x, f[1].y, f[1].z)

  vertex(f[2].x, f[2].y, f[2].z)

  endShape(CLOSE)

}

​

function reg_v4() {

  let p1 = createVector( 1, -1,  1)

  let p2 = createVector(-1, -1, -1)

  let p3 = createVector( 1,  1, -1)

  let p4 = createVector(-1,  1,  1)

  return [p1, p2, p3, p4]  

}

​

function setup() {

  createCanvas(400, 400, WEBGL);

  noStroke()

  let [p1, p2, p3, p4] = rand_v4(50, 150)

  therock[0] = [ p2, p3, p4, fnorm(p2, p3, p4) ]

  therock[1] = [ p1, p4, p3, fnorm(p1, p4, p3) ]

  therock[2] = [ p1, p2, p4, fnorm(p1, p2, p4) ]

  therock[3] = [ p1, p3, p2, fnorm(p1, p3, p2) ]

}

​

function draw() {

  background(0)

  rotateX(frameCount*0.003)

  rotateY(frameCount*0.005)

  ambientMaterial(0,150,0)

  directionalLight(255,255,255,0,0,-1)

  drawFace(therock[0])

  drawFace(therock[1])

  drawFace(therock[2])

  drawFace(therock[3])

}

​

​

​

​

​

​

​