bld.begin(GL::QUAD_STRIP);
bld.vertex(0, 0, 0);
bld.vertex(0, 0, 0.01);
bld.vertex(c*par_dist, s*par_dist, 0);
bld.vertex(c*par_dist, s*par_dist, 0.01);
bld.begin(GL::QUAD_STRIP);
bld.vertex(0, 0, 0);
bld.vertex(0, 0, 0.01);
bld.vertex(c*par_dist, s*par_dist, 0);
bld.vertex(c*par_dist, s*par_dist, 0.01);