fix bug 278: geometry tutorial (transplanted from e96300b0a9a91f1ed926901f0915830ac41c9248)
fix bug 278: geometry tutorial
(transplanted from e96300b0a9a91f1ed926901f0915830ac41c9248)

pthulhu/eigen,cjntaylor/eigen,cjntaylor/eigen,cjntaylor/eigen,pthulhu/eigen,pthulhu/eigen,cjntaylor/eigen,pthulhu/eigen,pthulhu/eigen