Ticket #3735: redoing what is still OK

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29763 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Better use of zMin/zMax for picking

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@29764 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e