I WAS READING SOMEWHERE ON HERE, THAT WHEN USING POINTS OR COULDS TO BUILD PLANES, CYLINDERS, OR OTHER STUFF, THAT PROBE COMP SHOULD BE OFF BECAUSE OF A COSINE ERROR. WHAT ARE SOME EXAMPLES OF WHEN TO HAVE COMP ON, VS OFF?  I DON'T THINK I UNDERSTAND THIS AS WELL AS I WOULD LIKE. 

THANKS.