+int cmesh_push_attrib(struct cmesh *cm, int attr, float *v);
+int cmesh_push_attrib1f(struct cmesh *cm, int attr, float x);
+int cmesh_push_attrib2f(struct cmesh *cm, int attr, float x, float y);
+int cmesh_push_attrib3f(struct cmesh *cm, int attr, float x, float y, float z);
+int cmesh_push_attrib4f(struct cmesh *cm, int attr, float x, float y, float z, float w);