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[FWL]

Hello everyone,

While doing an exercise modelling a head I ran into the problem that the project file had an error when attempting to open it again. When I read the project file in a text editor I found faces with a negative integer/number. When I deleted these the project would open again. I filled the holes again with new faces and saved the project and the problem was gone. I still have some questions relating to this problem though:

- How do these faces arise? Just bad beginner modelling or are there other triggers?
- Can switching between versions of anim8or cause this?
- Can converting to subdivision and back to mesh again cause this?
- And how can it be that filling the holes with the same faces again doesn't result in negative integers/numbers?

To illustrate  I attached the broken project file, the file with the corrupted faces deleted and the repaired file. It's a beginners attempt to learn edge flow topology so it isn't pretty ;-)

Thanks again for your help!

FWL

[Steve]

This is caused by a bug in Anim8or, I assume. Those numbers represent an index for the texture coordinate which should never be negative. Do you remember if you used and texture coordinate tools? Can you recreate the problem?

Switching versions should not cause this. If an older version doesn't recognize something it normally ignores it or, occasionally, rejects the file.

I'd like to fix the problem but I need to be able to recreate it first.

[FWL]

Hi Steve,

No I didn't use any uv tools, at least not as I remember. I wil try to recreate it. How can I show the history of the edits? Is there a log file I can generate, or should I ramp up the undo history and can I export that in a way?

The tools I used besides the normal tools like move and extrude of course were point slide, non uniform scale on edge loops to straighten them out, bevel on edge loop to create two edge loops.

And I've converted the subdivision model back to mesh and back again a couple of times with subdivisions set to zero when converting back to mesh.

[Steve]

FWL: I made a special build which can check the integrity of more Anim8or internal structures. You can download it here: v1.01.1367+, March 12, 2020: http://www.anim8or.com/download/preview/files/animcl1367+.zip

To enable structure checks, check the "Options->Debug->Check Structures" command in the menu before loading your project. Then when you are editing it will continuously check for errors in the data structures, including negative normal and texture coordinate indexes.

[FWL]

Hello Steve,

Thank you for the test version of anim8or! I will try it out. I repeated the excersise with the 3d head and ran in to the same error again. It happened when I extruded the three connected faces at the tip of the nose and then scaled them down. I was working in subdivision mode with the working subdivision set to the default of 2. After scaling the three new faces at the nosetip, they became a hole (this is also something that happens once in a while in subdivision mode). I then switch to object mode and set the working subdivision to 0 and entered Point edit mode again. The new face now did show. Right after that I did a save and tried to reopen and got the error message. Two faces have a negative integer in their values. They are in the proximity of the faces I edited but not the edited faces themselves. The two faces with negative integers do border on/adjoin a face I did an edge flip on to redirect the edge flow over the nosebridge.  I don't know if this information is useful in indentifying the issue. If I find something new with the test version I will let you know.

[FWL]

Hi Steve,

I've tried some modelling with the check structures on and the error ocurred again. I got a pop up warning for bad uv coordinates, when I used the flip edge tool in subdivision mode. So considering the previous occurences of this issue I've got the feeling it has something to do with the edgeflip tool. I've attached both the corrupted file and the repaired file. 

[Steve]

Good information. I'll try to reproduce it. But can you post the .an8 file just before you do the flip edge as well? That will make it much easier to find. It might work to use the Undo tool when the error occurs.

[FWL]

I'll see what I can do. Undo as I recall doesn't work. It undos the flip edge but not the face coordinate problem. When undo-ing and saving you still get the error at reopening. But I'll see if I can save after each editing step and create the pre fatal step history this way.

[FWL]

Steve, I have a file just before the error pops up. When you flip the edge selected on the image attached then you'll get the error. I hope it's helpful.

[Steve]

This should definitely, but, sorry, I can't see which edge is selected in the image.

[FWL]

No, I'm sorry. Here is a printscreen with the mesh visible

[Steve]

Perfect! I can reproduce the error, so I should be able to fix the problem. I tried a bunch of edges from the front view but not from the side vew.

Ill post a new build after I fix it.

[FWL]

Thanks and good luck!