I've seen this confusion crop up multiple times at my FLGS and the recent Regional, so I put together a thousand words on the subject that I hope aren't too pedantic.

This came up in a recent game...but do you measure closest to closest in leu of arc? So if there is an obstacle just outside of your Fire arc but other de between you and the target, is the line traced along your arc or through obstacle?

We reasoned arc overrides arbitrary closest to closest.

Also range might happen that a part you can't see is range 1 but your arc LoS is range 2.

This came up in a recent game...but do you measure closest to closest in leu of arc?

No. You measure the range, and check for obstacles, using the shortest line you can shoot along. That's a separate rule with its own (literal) corner cases, though, and I didn't want to get mired in that one while clarifying this one.

Range for attack is always measured in arc save for a 360 or 180 or split arcs

Range for attack is always measured in arc save for a 360 or 180 or split arcs

With a note that there are no 360 arcs, he means weapons that can fire outside of their arc.

Thanks Quarrel for putting this together. It's something I've always intuitively understood, but I've got some wierd looks from some opponents when I've tried to explain the geometry to them. This picture should make it crystal clear for everyone.