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Why are vertex indices randomly written out in FBX and OBJ and how can I avoid that?
Posted: 16 July 2021 11:27 AM   [ Ignore ]  
Total Posts:  2
Joined  2021-02-07

For context: we are working on 3D assets for a game in UE4 which is reading out the UCX collision element index for some functions. But since the FBX files we get from Cinema 4D do not have reliable vertex indices our pipline breaks.
I’m using R24.037

So how can I make sure, that the exports are consitent to the vertex structure in Cinema 4D?

For example:

I created a cube and made it ediable, then exported it to FBX.
These are the vertices and the corresponding index as written in the FBX:

Vertices: *24 {
            a
: -100,-100,100,-100,100,100,100,-100,100,100,100,100,100,-100,-100,100,100,-100,-100,-100,-100,-100,100,-100
        } 
        PolygonVertexIndex
: *36 {
            a
3,1,-1,2,3,-1,7,5,-5,6,7,-5,5,3,-3,4,5,-3,5,7,-2,3,5,-2,1,7,-7,0,1,-7,2,0,-7,4,2,-7
        } 

Then did the same thing again. Cube, editable, FBX. This was the result:

Vertices: *24 {
            a
: -100,-100,100,100,-100,100,100,-100,-100,-100,-100,-100,-100,-99,100,100,-99,100,100,-99,-100,-100,-99,-100
        } 
        PolygonVertexIndex
: *36 {
            a
1,0,-4,2,1,-4,4,5,-8,5,6,-8,0,4,-8,1,5,-5,2,6,-6,3,7,-7,3,0,-8,0,1,-5,1,2,-6,2,3,-7
        } 

And the cubes vertex structure as an attachment.

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Posted: 16 July 2021 03:53 PM   [ Ignore ]   [ # 1 ]  
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Joined  2011-03-04

Hi severin.walker,

I have tried to reproduce it here (Mac; FBX 7.7 2019), and if I export it as a text file, I get the same readout for all exported and reimported cubes.
What I don’t get is that a value of 100 goes to 99.

My suggestion, check with the tech support:
https://www.maxon.net/en/support-center

However, if you like me to explore it more, I’m happy to do so. I can send an upload link.

My best wishes

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

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Posted: 16 July 2021 09:40 PM   [ Ignore ]   [ # 2 ]  
Total Posts:  2
Joined  2021-02-07

Thank you very much for trying to replicate this.
I think I will take you advice and contact support.
It is really puzzling.

Could you maybe provide me with the FBX text file so I can make a few comparisons?

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Posted: 16 July 2021 10:12 PM   [ Ignore ]   [ # 3 ]  
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Hi severin.walker,

Of course, I can share that. I have screen captured the whole process: Create a cube, export [01], and reimport, then export [11] both. All files are in the link.

Examples and screen capture
https://www.amazon.com/clouddrive/share/OiRb5uwAozWUB5u0AiSU6v9fAJa3dxKQdhkCBz4HCB1

Let me know if you need anything else to explore this. I am happy to look into it.

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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