AC3D Forums Convex Hull problems
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 16th June 2006, 06:30 PM #1 Stiglr Senior Member Professional user     Join Date: Feb 2004 Location: Portland, OR Posts: 604 Convex Hull problems Why is it that sometimes, when I try to create a convex hull from a pair of cross sections, the software often just 'decides' which vertices to ignore completely in making a new shape? For example, say I'm modeling a vertical stabilizer and rudder. I make a poly shape of the filet of the piece and another of the profile of the piece and arrange them perpendicular to each other in the proper place to describe the entire tail unit. Now let's say the trailing edge of the rudder has a nice curved edge leading towards where it will join the fuselage... I create the polys of both shapes, select all the vertices, and do a Convex Hull. The result I get is a straight line between the trailing edge, and the polys I'd set to describe the scalloped edge just aren't there anymore. The rest of the shape is exactly what I had in mind. What's the trick to getting this feature to obey instructions? __________________ Flight Sim Project Contributor My Gaming Rig: i5 2500K Quad-Core CPU at 3.3GHz MSI P67A-C43 mobo 4GB of PC12800 DDR3 memory Windows 7 1GB Galaxy GeForce GTX550 Ti video card GeForce 270.61 drivers (4/2011) Cougar joystick/throttle combo CH Pedals
 17th June 2006, 02:08 AM #2 Andy Administrator Professional user     Join Date: Jun 2003 Posts: 4,451 Re: Convex Hull problems The key word is 'convex'. If you imagine shrinking a rubber balloon over the vertices, any vertices which are not 'on the edge' will not touch the balloon. For a vertex to be part of the final shape, it must 'stick out'. If there's a vertex you need to have in the final shape, move it outwards, do the convex hull, and then move the vertex back. It's more like putting a (deflated) balloon around the vertices, rather than 'vacuum packing'. Last edited by Andy; 17th June 2006 at 03:29 AM.
 17th June 2006, 08:13 PM #3 Stiglr Senior Member Professional user     Join Date: Feb 2004 Location: Portland, OR Posts: 604 Re: Convex Hull problems I'll try that, thanks!!! __________________ Flight Sim Project Contributor My Gaming Rig: i5 2500K Quad-Core CPU at 3.3GHz MSI P67A-C43 mobo 4GB of PC12800 DDR3 memory Windows 7 1GB Galaxy GeForce GTX550 Ti video card GeForce 270.61 drivers (4/2011) Cougar joystick/throttle combo CH Pedals
 19th June 2006, 01:22 PM #4 captainj2410 Senior Member Professional user     Join Date: Aug 2005 Location: Captain's Quarters, Deck 1 USS Avenger NX-101468 Posts: 792 Re: Convex Hull problems This is the point at which I do a manual hull... __________________ http://jamietakahashi.deviantart.com
 26th June 2006, 09:12 PM #5 nightoftheroundtable Senior Member Professional user     Join Date: Mar 2006 Location: elma washington Posts: 805 Re: Convex Hull problems hmmmm. I never really thought of doing a convex shape hull design. ooh interest. I think I will do a convex hull design in my next project.

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