The first example shows 3 points and their barycentric coords wrt a line segment. One of the points is outside the line segment, and it’s bar. coord. is negative, but that seems to be ok.
(‘Bad’ things might happen when some code handles these guys and doesn’t anticipate them being negative.)
mathworld.wolfram.com say lots of things about barycentric coordinates. Couldn’t find anything about outside the triangle, but might have missed it as well.
To recap, it looks like it should be safe, at least when used reasonably, ie, when your point outside the triangle doesn’t actually goes to infinity. But then again, in graphics you shouldn’t be getting that anyway.
I’m a bit confused by your last question. Could you please repeat what’s the input for this calculation you want to do? I assume the output will be the new BC. You say you want to find that based on old BC and old position. What else will be known?
mad
[This message has been edited by madmortigan (edited 02-24-2004).]
Yes, you can use barycentric cooordinates to determine any point in the universe. The cool thing about barycentric coordinates is that all of them are positive when inside the object.