public void setIntensities(float ar, float ag, float ab, float aa,
                             float br, float bg, float bb, float ba,
                             float cr, float cg, float cb, float ca) {
    vertices[0][R] = ar;
    vertices[0][G] = ag;
    vertices[0][B] = ab;
    vertices[0][A] = aa;
    vertices[1][R] = br;
    vertices[1][G] = bg;
    vertices[1][B] = bb;
    vertices[1][A] = ba;
    vertices[2][R] = cr;
    vertices[2][G] = cg;
    vertices[2][B] = cb;
    vertices[2][A] = ca;
  }