BWAHAHAHAHAHAHAHA ROTATION. IT HAS BEEN DID.

rotation1.pde

/*
 rotating some mfkin thing with a mfkin matrix ok bro it's gonna happen
 TODAY IS THE DAY
 March 19th, 2014
 
 TODAY WAS THE DAY THAT I DISCOVERED THAT PROCESSING COORDINATES WERE THROWING ME OFFFFF
 APRIL 10th, 2014!!!!!!!
 */
int w = 300;
int h = 300;
int cx = w/2;
int cy = h/2;
Trianggl t;
float theta;
color c;

void setup() {
  size(w, h);
  background(0);
  t = new Trianggl();
  theta = .1;
  c = color(200, 200, 0);
}

void draw() {
  background(0);
  //crucial element
  //i could've used a translation matrix but i was lazy
  translate(cx, cy);
  float[][] r = getRotationMat(theta);
  PVector p1 = getNew(r, t.v1);
  PVector p2 = getNew(r, t.v2);
  PVector p3 = getNew(r, t.v3);

  t = new Trianggl(p1, p2, p3);
  t.drawT(c);
}

/*
this was a test because i was not sure if i understood how matrices were being applied
 obviously i did because i know what matrices are. but just in case.
 */
float[][] getScalingMat(float scale) {
  float[][] scaling = new float[2][2];
  scaling[0][0] = scale;
  scaling[0][1] = 0;
  scaling[1][0] = 0;
  scaling[1][1] = scale;
  return scaling;
}

float[][] getRotationMat(float theta) {
  float[][] rotation = new float[2][2];
  rotation[0][0] = cos(theta);
  rotation[0][1] = sin(theta);
  rotation[1][0] = sin(theta);
  rotation[1][1] = cos(theta);
  return rotation;
}
/*
gets new triangle coordinate
*/
PVector getNew(float[][] r, PVector p) {
  float x = p.x*r[0][0] - p.y*r[0][1];
  float y = p.x*r[1][0] + p.y*r[1][1];
  PVector pp = new PVector(x, y);
  return pp;
}

/*
added this in so that i can make use of my scaling matrix
*/
void mouseReleased() {
  float[][] r = getScalingMat(1.5);
  PVector p1 = getNew(r, t.v1);
  PVector p2 = getNew(r, t.v2);
  PVector p3 = getNew(r, t.v3);

  t = new Trianggl(p1, p2, p3);
  theta -= 0.02;
}

Triangle.pde

class Trianggl {
  PVector v1, v2, v3;
  Trianggl() {
    /*
    default constructor
     generates an eq.tri w/ radius 20
     */
    v1 = new PVector(0, -20.0);
    v2 = new PVector(-1*(20*sin(PI/3)), 10.0);
    v3 = new PVector(20*sin(PI/3), 10.0);
  }
  Trianggl(PVector p1, PVector p2, PVector p3) {
    v1 = p1;
    v2 = p2;
    v3 = p3;
  }
  void drawT(color c) {
    stroke(c);
    line(v1.x, v1.y, v2.x, v2.y);
    line(v2.x, v2.y, v3.x, v3.y);
    line(v1.x, v1.y, v3.x, v3.y);
  }
}