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Face normals spontaneously reversed...model is insode-out it seems!

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Message 1 of 11
jeffpike6221
667 Views, 10 Replies

Face normals spontaneously reversed...model is insode-out it seems!

Hope I accidentally tripped a setting somewhere and this isn't a more serious problem.

 

Had major issues with an IPN file not opening today, so I but the bullet and trashed 2 days of work in the IPN to start from scratch.

 

I've been very careful to only set up my assembly model (over 650 unique parts, 2500-ish instances) with view representations to keep everything as simple as possible.  Even shrinkwrapped several subassemblies.  Things were chugging along fine (slow, but OK given IPN's limitaitons that I'm discovering more of every day), but this morning a complex IPN with 5 exploded views just decided not to open.  No error messages, no warnings, just wouldn't open.  The Browser would show the explosion views, the part counter racked up the parts in the lower right hand corner, but after all the parts loaded into memory (not displayed on screen), the hourglass spun.

 

Tried sorting things into pack-n-go, tried rebuilding the assembly using Rebuild all...even opend the IDW file associated with the IPN with deferred updates, but as soon as I would turn updates on again, everything froze.

 

So I gave up.  I decided to rebuild the complete IPN, so I dove back into the model file, and noticed that I forgot a washer.  Easy enough, just drop it in from content center...but when I was finished with Autodrop, it looked like it disappeared.  The instance was in the browser, but it wouldn't show in the Graphics screen.

 

Or so I thought.  Actually, it WAS in the screen, just buried inside the solid part that it was supposed to be sitting on top of.  Strange, I tried to delete it thinking maybe I grabbed the hole edge incorrectly during autodrop. 

 

BAD MOVE.

 

I got a vomit of warnings about invalid constraints.  About 15 of them.  Every one had to do with mating surfaces or insert constraints not being proper (this model has been  a work in progress for about 2 months, and those same constraints were never invalid).

 

After digging, it appears that many, but not all, of my parts have reversed normal directions on all faces.  In other words, a mate constraint to a particular face now acts as a flush constraint.  An insert opposing acts like an insert in same direction.  Worst of all, many of those invalid constraints were for certain origin planes to line up.  Now some of my origin planes are all reversed too, it's not just physical parts.

 

I'm really getting ticked off here.  Tried restoring the model from a couple days ago (when everything was fine) but no joy, still inside-out parts. 

 

Am I screwed?

 

For now, I've suppressed all the offending constraints, but I can't make any real progress any more.  I just can't keep faking flush constraints by using mate constraints, and AutoDrop for content center is useless for fasteners now.

 

Ugh...

 

J

 

(Inv Pro 2012, WinXP64, Dell Precision M6500)

10 REPLIES 10
Message 2 of 11
jeffpike6221
in reply to: jeffpike6221

Update:

 

This appears to be related to a derived shrinkwrap from one of the assemblies...the LOD of the assembly, when active, shows the surfaces with correct normals.  The Shrinkwrap substitute LOD, though, is when all the surfaces turn inside-out.

 

I am thinking that somehow the tweaks in the IPN file that got corrupted in some way forced the shrinkwrap substitute (which was referenced in the IPN) to invert all its normals.

 

Crazy thing is that even when I completely delete the shrinkwrap IPT substitute part, and re-derive the whole thing from teh base assembly, the resulting shrinkwrap still has inverted normals.

 

I am going to try this on a smaller assembly file and see if I get the same thing...I think maybe this is a bug in Inventor?

 

J

Message 3 of 11
jeffpike6221
in reply to: jeffpike6221

After more digging (and more frustration with a certian ipn file), I decided to run the scanner that Autoloader uses when uploading a bunch of files to Vault (not through the Inventor Vault utulity).

 

I selected the master assembly, scanner ran scans on the whole thing, and it turns out that there was an "internal error in scan" on ANY assembly or weldment that had a substitute LOD associated with it.  Name of substitute LOD, location in file structure of the substitute part...none of those things mattered.  Only that there is a substitute LOD available (not even active, just available).

 

Now MOST of those files behave just fine when I'm using them, i.e. substitutes work as they should, LOD's are properly linked to master assemblies.  I would never have known there was any kind of issue with most of those files, and for the most part, there isn't.  But I have a suspicion that the Autoloader's Scanner is trying to tell me something about the substitutes, and that the issue might very well be related to my corrupted IPN file and my backwards face normals on some of these substitutes.

 

Any thoughts?...

Message 4 of 11

We did have reports of this in earlier versions of Inventor but released a fix to prevent the issue from occurring again. What version of Inventor were these files created in? Have they all been migrated to the current release?



Dave Anderson
Sr. Support Engineer– CAM
Autodesk, Inc.


Message 5 of 11

About 95% of the parts and all of the assemblies and weldments were built inside Inv 2012.  About 5% of part files were constructed in Inv2010, but everything has since been migrated (long ago).

 

The problem is absolutely related to shrinkwraps, which have a frustrating habit of just not working every now and then.  For whatever reason, my shrinkwraps just don't want to stay right-side out when they get a little more complicated.  My model files are all clean, my assemblies are all buttoned up. 

 

Don't get me wrong, MOST of the shirinkwraps are fine.  It's juste every once in a while...

 

I've just given up and am working in the top assembly with a LARGE subassembly that I just won't shrinkwrap (well, large by my standards, maybe not by others around here...).  Memory is good as long as I don't have too much open at once.  Inventor will eat up about 2.5-3M of my physical memory, and I guess around 3-4 of paged space with this assembly not shrinkwrapped.  If I could get it to successfully wrap, I think I could bite off about half a Meg.

 

J

Message 6 of 11

If I'm not mistaken the issue was with 2010 parts. In some cases the "Normal" side of a workplane was flipping.

 

 If you'd be interested in providing a set of files for me to look at just let me know and we can take this off-line.



Dave Anderson
Sr. Support Engineer– CAM
Autodesk, Inc.


Message 7 of 11
karthur1
in reply to: dave.anderson

Dave,

I came across a similar issue.http://forums.autodesk.com/t5/Autodesk-Inventor/Change-Part-Length-Part-flips-and-it-messes-up-const...

 

What I noticed was when the parts were brought into 2011, thats when the parts would flip.  2009, 2010 did not have the issue, but 2011 does.  Seems like the issue was fixed in 2012 also.

Message 8 of 11
dave.anderson
in reply to: karthur1

Precisely.



Dave Anderson
Sr. Support Engineer– CAM
Autodesk, Inc.


Message 9 of 11
tsingi
in reply to: dave.anderson

How does one flip a face upwards again?
Message 10 of 11
JDMather
in reply to: tsingi

Can you attach the file(s) here?


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Message 11 of 11
tsingi
in reply to: JDMather

The drawing is huge. Its Hong Kong airport, and possibly the worst CAD I've seen. For example, I found arcs depicting the edge of roadways that were expressed as regions and apron surfaces described as 3d faces. What I'm attaching is an array of circles and polygons that define the touchdown zone lighting. These were very complex and mixed up block references, now they are circles. I have colored the circles that are facing the wrong way, red. I've deleted the rest of the drawing, it is very large, and somewhat proprietary. I think I understand what the normal (xyz) attributes are for now, they describe a point on a unit circle that is perpendicular to the plane of the face. (from the centroid?) I don't need any of that, I need a 2D drawing that does not incorporate any 3d information at all. I'd like to know how to set the normalization point back to 0,0,1

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