private void thick_point(float x, float y, float z, // note floats
                             float r, float g, float b, float a) {
      spolygon.reset(4);
      spolygon.interpARGB = false;  // no changes for vertices of a point

      float strokeWidth2 = strokeWeight/2.0f;

      float svertex[] = spolygon.vertices[0];
      svertex[TX] = x - strokeWidth2;
      svertex[TY] = y - strokeWidth2;
      svertex[TZ] = z;

      svertex[R] = r;
      svertex[G] = g;
      svertex[B] = b;
      svertex[A] = a;

      svertex = spolygon.vertices[1];
      svertex[TX] = x + strokeWidth2;
      svertex[TY] = y - strokeWidth2;
      svertex[TZ] = z;

      svertex = spolygon.vertices[2];
      svertex[TX] = x + strokeWidth2;
      svertex[TY] = y + strokeWidth2;
      svertex[TZ] = z;

      svertex = spolygon.vertices[3];
      svertex[TX] = x - strokeWidth2;
      svertex[TY] = y + strokeWidth2;
      svertex[TZ] = z;

      spolygon.render();
    }