/* tri,l, base, r, sphere */
roam_triangle_add(sl, sr, self->t.l, br, sphere);
roam_triangle_add(sr, bl, self->t.r, sl, sphere);
/* tri,l, base, r, sphere */
roam_triangle_add(sl, sr, self->t.l, br, sphere);
roam_triangle_add(sr, bl, self->t.r, sl, sphere);