feedback_vertex(fs->ctx, draw, prim->v[0]);
feedback_vertex(fs->ctx, draw, prim->v[1]);
feedback_vertex(fs->ctx, draw, prim->v[2]);
feedback_vertex(fs->ctx, draw, prim->v[0]);
feedback_vertex(fs->ctx, draw, prim->v[1]);
feedback_vertex(fs->ctx, draw, prim->v[2]);