[BUG] Crash on export with modifiers

[Dprasni]

Ver 1.0.4

Blender crashes when I try to export a model with several modifiers in the list. Works fine and fast with a 2mil poly model when the modifiers are applied but fails when they are not applied and I try to export.

[speculative-artefact]

hey thanks for reprting another issue @Dprasni ! can yo uattach a screenshot of the modfiers you're using that causes the crash?

[Dprasni]

[speculative-artefact]

great thanks, i'll look into this asap, might take a couple days

[speculative-artefact]

hey @Dprasni, i've added a couple things. first i've tried to optimise the process of applying multiple modifiers on export. second i've added an option in the interface that allows you to choose how you want to manage modifiers on export, ignore modifiers, apply visible modifiers, or apply render modifiers. the default is apply visible which is what i was doing in the background before. i hope that addresses your problems! please update the extension and let me know if there is any improvement.

[Dprasni]

Would you like for me to continue here with the new version 1.2.1 or to open a new issue?

[speculative-artefact]

if it's still related to the crashing we can keep it in this thread. if it's another issue let's open another thread and close this one.

[Dprasni]

Ok so, Crashing related + very long export time (on version 1.2.1)

This time I'll attach a test file i tested with (scene Cliff),

Broken Houses Export testing

Cliff mesh export - around 2 mil poly with modifiers

• 1.76 (pre-appliedModStack)
• 7.91 (1.29 exporting time, manually applying then export)
  1st attempt export with unapplied modifiers
• 3 minutes then Bsod (thrashed my cpu like mad - R9 5900, here i had multiple browsers open in the bg which also took a bit of ram)
  2nd attempt export with unapplied modifiers
• 2 minutes then crash (task manager view, thrashed my cpu 10 seconds at 100% before crashing, it ate all my ram, have 32gig while 9gig is used normally with open file, no browsers or other software opened after the BSOD)

Test File:
https://drive.google.com/file/d/1INO29pYTG19a8As9m-8Bx0h6Y37JxnY4/view?usp=sharing
(200 meg file had to upload to gdrive)

[speculative-artefact]

ok, thanks for sharing your file! i was able to identify the issue was actually with scaling. i was manually scaling the mesh before export. this allowed me to scale for all export types but it was using A LOT of memory when scaling dense meshes, especially like yours at 100x. i'm now passing the scale as a parmeter to the export operator which means i can't support scale for GLTF and USD formats as then don't have that parameter but i think it makes the add-on much more stable.

please update and try it out. i'll leave the issue here open for now until you confirm everything is working well.

i learned a lot while trying to fix this so thanks again!

[Dprasni]

The scale removal could be a problem.

Thing is, now exports go fast without any scale applying, this creates a problem when importing to Unreal as they get imported as 0.01 scale (FBX roughly) so the models are very tiny as opposed to ther real size in blender by a factor of 100.
Changing the M/CM has no effect on export (nor did it have previously i think), the scale was 100 previously because unreal is in cm and Blen in m, so i had to scale it up on export to get the correct scale of 1in unreal (i don't normally touch the scale scene value when doing anything for unreal in blender because i want to fiddle with as little settings as possible)

Does the addon work, yes, no crashes and quick apply of the stack when exporting, which is great.
On the other hand the lack of scale forces me to scale the model import to 100 on unreal import, which could have potention issues down the road in engine when scale is beyond 1.

Don't know if there is any easy solution to have the ability to apply stack then scale to a x factor without that huge memory syphon

[speculative-artefact]

damn, ok i'll double check the scale. it should work, and using cm should have an effect. but i haven't tested the full end to end Blender to Unreal flow since i made these changes. will look into it this weekend.

[speculative-artefact]

hey, i just tested exporting fbx with scale 1, 50, and using cm and m units. all worked as expected for me and were very fast.
can you test again? make sure you're using v1.2.2

btw i only removed scale for GLTF ans USD formats because they don't support scale as an export parameter. are you using those formats too?

[Dprasni]

New test - a bit more detailed

Cliff face (added a new stack to the base with no modifiers/clean mesh - Decimate 0.1, Remesh voxel 0.3 smoth) base mesh 2 mil poly-tri
Exporting as FBX (best game compatibility) - ram usage only jumped by around 700 megabytes (seems like a good number)

• 67.50s (Meter scale 1)
• 65.73s (Meter scale 100)
• 65.81s (Centimeter scale 1)
• 66.41s (Centimeter scale 100)
  Without the stack it would export in under a second a 130k mesh (or a clean 2 mil mesh 1.42s)
  (the export length is a normal number as blender keeps recomputing everything all the time from beginning in the mod stack, which is normal for blender since we cant bake the result before exort without going to GN)

New test with GN bake (Bake node applied as last member of the stack, then baked - keeps the final shape from modifiers before it)

• 66.47s (baked in GN with modifiers before bake still turned on)
• 0.21s (baked GN with modifiers before it turned off)
  Looks like blender keeps recomputing everything in the stack on export even if theres a GN bake node at the end (that seems to be the default behavior)

Importing all to Unreal (version 5.4) at the scale of 1

• All are same size of 0.01

[speculative-artefact]

hmm ok, can i ask you to test the export time and scale with the mesh you shared with me and let me know if that works as expected without crashing? this might be a separate issue. not sure yet

[Dprasni]

In the previous post i tested with the same file/mesh, just used different modifiers the 65-ish seconds test, no crashing, memory footprint only went up 700 megs on export process (these include with different scaling numbers 1/100 and m/cm on a 2 mil poly mesh, all 4 variations results were the same within the margin of error).

Unless you want me to test it in a specific way? (or the same mod stack as the first time)

ADDENDUM
I tried to export with the integrated export FBX from blender, the export is 10s long as opposed to the addon which is 60s long, with the GN node at the end of the stack.