triCol

int num = 1, frms = 100;
float theta;
color[] col = {color(255, 50, 0), color(0, 255, 50), color(0, 50, 255)};

void setup() {
  size(540, 540, P2D);
}

void draw() {
  //background(0);
  noStroke();
  fill(20, 30);
  rect(0, 0, width, height);
  for (int i=0; i<num; i++) {
    float offSet = HALF_PI/num*i;
    drawTriangle(offSet);
  }

  theta += TWO_PI/frms;
  if (frameCount> 100 && frameCount<=(100+frms)) saveFrame("image-###.png");
}

void drawTriangle(float offSet) {
  float r = map(sin(theta),-1,1,50,150);
  pushMatrix();
  translate(width/2, height/2);
  rotate(theta+offSet);
  beginShape();
  for (int i=0; i<3; i++) {
    float x = cos(TWO_PI/3*i)*r;
    float y = sin(TWO_PI/3*i)*r;
    fill(col[i]);
    vertex(x, y);
  }
  endShape();
  popMatrix();
}