Processing calculate inverse of screenX/screenY (WIP, not working perfectly)

gistfile1.java

void mouseDragged() {
  
  if (mouseButton == RIGHT) {
    float z = screenZ(k.x,k.y,k.z);
    println(z);
    PMatrix3D proj = ((PGraphics3D) this.getGraphics()).projection;
    PMatrix3D transform = ((PGraphics3D) this.getGraphics()).modelview;
    PMatrix3D a = transform.get();
    PMatrix3D b = proj.get();
    a.invert();
    b.invert();
    PVector m = new PVector((float)mouseX/width*2-1,  (float)(height-mouseY)/height*2-1, 1);
    PVector aa = a.mult(b.mult(m, null), null);
    PVector pm = new PVector((float)pmouseX/width*2-1,  (float)(height-pmouseY)/height*2-1, 1);
    PVector paa = a.mult(b.mult(pm, null), null);
    PVector d = aa.sub(paa);
    println(k, aa, paa);
    k = k.add(d.mult(z));
  }
}