Any coordinate system that lies on a part causes some tessellated entities to have non-positive (<= 0) coordinate values. This can cause a problem with programs that only use positive coordinates. To avoid this problem, select a coordinate system that gives all positive values. If the part produces nonpositive values, the Creo application notifies you and prompts you to continue. If you type NO, it quits the process, enabling you to create or select a different coordinate system.