Bug in area when taking difference between certain shaped facets

I was trying to create a round hole in a facet by taking the difference bwetween a square and round facet. It summed the areas rather than subtracting the inner one. This throws off all the calcuated values that relies on area. Facet 1 & 2 are the original, and 3 the difference.

Taking the difference between a round and square facet to create a round hole.

It worked ok if the smaller facet was square rather than round. My fix was to create the hole manually from four seperate facets, by slecting the vertices manually in the correct order. I think molflow has a problem handling shapes that are too "concave". The sum of the areas of these four new facets is correct.

Hole in square using 4 sections

Dear Alan, I didn't reply to this one...

...I'll have a look in february, when I'll be back at CERN. Concave facets are relatively rare in Molflow so indeed it's possible that the area calculation has a bug. Meanwhile, thanks for the report and the screenshots.