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Old 09-26-2012, 06:47 AM   #1
jobwallis
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Do i need to weld verts?

HI I have received a mechanical engineering model in STL format.
It is showing 800k tri's.
The only way to to get it to import was to turn off weld verts (seemed to be crashing it) and turn off autosmooth.
Upon successful importation i started welding verts.
This didn't result in a reduction of tris (no coplanar faces it seems) so i aborted (plus i got bored
My question is will leaving this model unwelded reduce performance or result in increased render times? Test renders (which render around 6 seconds (good for me)) show resolution of model is good enough that i wont need smoothing groups.
I will be rendering with MR w indirect illumination probably some volume lights and fog.
I am noticing that selecting parts of the model to break it up is slowing the machine.
win 64, 16 gig RAM, 3G vRAM, 8 cores i7 2.3 GHz
I can reduce geometry by deleting unseen elements and reduce by maybe 25%. Deleting unseen (non rendering) elements will increase workflow performance but not speed up rendering, correct?
 
Old 09-26-2012, 07:50 AM   #2
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I would be surprised if you didn't get a performance boost by welding verts - after all with 800k tris, that's a shed load of verts you'll be holding in memory, even IF all the coincident ones have been welded.
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Old 09-26-2012, 08:21 AM   #3
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thanks Matt
I am seeking to lose my self in thoughtless tasks.
...thus i am reducing. Have already reduced by 50%.
Once this is done i will weld.
When you say performance increase i understand this to mean realtime display in software display response time as opposed to render times. As most of this stuff I am deleting is not seen anyway would it add to render times?
cheers
 
Old 09-26-2012, 12:01 PM   #4
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Those verts will still all have to transformed when you render. But since everything else will take far longer you probably won't see much of an increase. Viewport performance is likely to improve more.

You should be able to weld all the verts at once. Select all the objects, apply an edit poly modifier to them all at once. Select all verts, hit weld. Only the verts within each object will get welded. You won't end up welding one object to the next. Then just collapse/ convert to editable poly and all the objects will be separate.

You might find it still crashes if you run out of memory like it did on import, but in my experience it's more successful once the model is already loaded. Give it a go, but remember to save first.
 
Old 09-26-2012, 12:03 PM   #5
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Also if you need it smoothed you won't be able to use smoothing groups unless you weld first. Normals might have imported ok even on unwelded verts (I'm sure Eric will pop in to give some clarification on that), so it might look ok as is. But if you need to edit it that could break (again, Eric knows which tools ruin imported normals).
 
Old 09-26-2012, 12:20 PM   #6
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Thanks Robin
Has only just occured to me how lucky i was that all normals imported correectly.
I have finished reduction. Reduced from 800k down to 400k triangles.
This was done manually by deleting all internal elements that would not been seen in animation.
Big difference was verts reduced from 2.4 million to 191k via welding.
Welding was done in lots of 100k verts as more seemed to result in (Not Responding) hang.
Object was supplied as one mesh and i have broken into moving parts.
FYI 'crash' on import was apparently not memory related. Was just hanging. Still approx 8 gig available. Noticed that welding only users 1 processor.
Smoothing was simple once welded.
Will remember your multi object weld technique for next time.
thanks mulchly
 
Old 09-26-2012, 01:39 PM   #7
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Quote:
Originally Posted by robinb
Also if you need it smoothed you won't be able to use smoothing groups unless you weld first. Normals might have imported ok even on unwelded verts (I'm sure Eric will pop in to give some clarification on that), so it might look ok as is. But if you need to edit it that could break (again, Eric knows which tools ruin imported normals).
Yeah normals (vertex normals, not face normals/smoothing groups) are a pain in 3ds max with inconsistent support depending on the base object modifiers are on. If you want good results in reduction and welding you should use ProOptimizer in 3ds max 2012 or 2013. It provides support for vertex normal retention and reduction. Also, if you enable merge verts with a tolerance of 0.0 it will weld all verts while preserving normals.

NEVER apply an Edit Poly to an object using vertex normals. It will disregard them as soon as the modifier is added. If you need to combine objects and retain normals DO NOT attach using base object or modifier. Instead use the Collapse Utility and collapse to a single mesh (only way to combine objects and retain normals without building a new object through scripting). I have plenty of posts here covering normals and normal support searching my user name and normals and you should get various posts/threads on the topic.

-Eric
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Old 09-26-2012, 01:39 PM   #8
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