Maya for 3D Printing - Rapid Prototyping
In this course we're going to look at something a little different, creating technically accurate 3D printed parts.
# 1 06-01-2012 , 11:56 PM
dre4mer's Avatar
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Bridge issue

Hi Guys,

Ok I've certainly used bridge before.... just not in Maya 2012. I'm just trying it for the first time. Bridge doesn't seem to be working?

The normals are facing the correct direction I've even tried deleting the faces and bridging the border edges of the holes together. Same thing. Is this just a bug or am I forgetting something here? Oh I also have deleted "ALL history" by type just in case, but still no joy.

user added image


Thanks for any ideas,

-Ethan


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Last edited by dre4mer; 07-01-2012 at 12:17 AM.
# 2 07-01-2012 , 12:24 AM
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This is normal behavior. This twisting is the result of the vertex ordering and happens all the time.

To untwist things go to the channel box and scrub the offset property of the bridge node.


"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
# 3 07-01-2012 , 12:27 AM
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Sometimes it happens, not sure why... here are 2 ways to fix it:

user added image

1) play around with the bridge offset setting in the channel box; if that doesn't work..

2) extrude one of the faces and then use merge vertex tool to join it to the opposite face

PS.: an easy way to see the normals is to go into Lightning in the main window and un-check 'two sided lightning'.. this way all the faces with wrong normals will display black. I usually set it up right away when i start new project, the green lines are just way to confusing..

# 4 07-01-2012 , 12:40 AM
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ah perfect thank you! A bridge offset of 3 works. Also I will use that other method to see the faces that's a great tip thank you very much!!!


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# 5 07-01-2012 , 12:40 AM
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It happens because of vertex ordering and there is little you can do about it. Just use the bridge offset property to untwist things.

Imagine the vertices on one face are numbered {1,2,3,4} and on the other face are numbered {10,11,12,13}. So vertex 1 snaps to 10, 2 goes to 11, and so on. There is only a 1 in 4 chance the verts will naturally snap to their correct partner and this of course is for a bridge with 4 verts if there are more there is an even lower chance the ordering will be correct.

So I find I have to use offset a lot.

But always check to see the normals are correct as this is the next most likely cause for a bridge to be twisted. One sure sign of reversed normals is when you scrub through all the possible offset values and the bridge refuses to untwist.


"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 07-01-2012 at 12:45 AM.
# 6 07-01-2012 , 01:33 AM
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Np Dreamer

@Ctbram: Interesting.. I always assumed it was just a glitch, good to know there's an actual reason for it.

# 7 07-01-2012 , 01:46 AM
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If you think about it, there is no way for Maya to know which edge you want connected to which (except maybe a proximity test, but even that could be wrong), so it picks a somewhat arbitrary metric, as ctbram described. Luckily maya gives you the control to change it how you want.

That being said, there are bridge glitches in maya. Sometimes the resulting faces appear invisible and are unselectable. Sometimes you can reassign the material, or sometimes you can undo and try again. Anyway, that wasn't the original question. Apologies.

# 8 07-01-2012 , 04:53 AM
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I just thought of a way that it actually could be fixed in most cases; but it's too long and technical to post here...

Not that anyone would be interested either. user added image


Imagination is more important than knowledge.
# 9 07-01-2012 , 05:09 AM
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Thanks for the explanation ctbram, I've certainly hit the normals issue before which is why this was baffling me. I have never hit this offset thing before which I don't get since I've been using Maya for months. Bridges either worked or didn't on account of the normals. So that won't happen again user added image

-Ethan


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Last edited by dre4mer; 07-01-2012 at 05:11 AM.
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