Author Topic: Weird Shadow artifact  (Read 2068 times)

2022-07-24, 14:32:53

aysigrub

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I am getting these weird shadow artifacts on a 3D model I converted from step to obj. The model is kind of messy as you can see on the right side of the image but the actual surface is smooth.
The ugly shadows only appears when there are small lights casting a sharp shadow. They do not appear when using a corona sky for example.

Any ideas?
Thanks

2022-07-24, 15:01:40
Reply #1

romullus

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That's messed up vertex normals. Most likely happened when you converted model to obj. If it's possible, try to render the model without converting it to polygons - you should get much better result.
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2022-07-24, 15:16:54
Reply #2

aysigrub

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That's messed up vertex normals. Most likely happened when you converted model to obj. If it's possible, try to render the model without converting it to polygons - you should get much better result.

Thanks! Im not sure how to open an .step file in C4D without converting it to polygons.. hmmm

2022-07-24, 15:30:45
Reply #3

romullus

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Sorry, can't help you with that, i'm a 3ds Max user. Max can open and render CAD objects without issues.

Maybe try to see if it's possible to retain vertex normals in the software where you are doing conversion and make sure that C4D does not override them in the process of model import.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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2022-07-24, 17:40:27
Reply #4

aysigrub

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Sorry, can't help you with that, i'm a 3ds Max user. Max can open and render CAD objects without issues.

Maybe try to see if it's possible to retain vertex normals in the software where you are doing conversion and make sure that C4D does not override them in the process of model import.

Understandable! Thank your for the information

2022-07-24, 20:26:35
Reply #5

burnin

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Thanks! Im not sure how to open an .step file in C4D without converting it to polygons.. hmmm
I can take a look. Just post it here or send PM.

2022-07-25, 13:15:08
Reply #6

JPeters

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CAD models are generally a pain to work with and this kind of artifact is actually quite common.

Some things that might help:
- Messing around with the phong tag (for instance disabling angle limit)
- Messing around with the normals tag (for instance deleting it)
- Importing with a higher resolution (so shorter max length).

That being said, usually it can be fixed with the above but some CAD models are simply broken and beyond repair. If you can, ask the person who exported the original STEP mesh for you to export it again with different settings.
« Last Edit: 2022-07-25, 13:25:38 by JPeters »

2022-07-25, 13:33:01
Reply #7

burnin

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Add to your arsenal. It's more than enough. 

2022-07-25, 14:37:45
Reply #8

Nejc Kilar

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CAD models are generally a pain to work with and this kind of artifact is actually quite common.

Some things that might help:
- Messing around with the phong tag (for instance disabling angle limit)
- Messing around with the normals tag (for instance deleting it)
- Importing with a higher resolution (so shorter max length).

That being said, usually it can be fixed with the above but some CAD models are simply broken and beyond repair. If you can, ask the person who exported the original STEP mesh for you to export it again with different settings.

Pretty much my experience with CAD files as well.

I would however like to add that you can also try splitting off the weird geo and try to retopologize it using one of the new retopo generators that are there in the newer Cinema 4D releases. Sometimes that can help. Sometimes. :))
Nejc Kilar | chaos-corona.com
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2022-07-25, 17:27:52
Reply #9

Philw

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I always put STP files through Moi3D to get more predictable meshes.

2022-07-28, 23:30:52
Reply #10

aysigrub

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I always put STP files through Moi3D to get more predictable meshes.

Thanks for all the tips! I was able to use Moi3D and exported a solid clean mesh!

2022-08-18, 11:03:11
Reply #11

Sebastien

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CAD models are generally a pain to work with and this kind of artifact is actually quite common.

Some things that might help:
- Messing around with the phong tag (for instance disabling angle limit)
- Messing around with the normals tag (for instance deleting it)
- Importing with a higher resolution (so shorter max length).

That being said, usually it can be fixed with the above but some CAD models are simply broken and beyond repair. If you can, ask the person who exported the original STEP mesh for you to export it again with different settings.

Pretty much my experience with CAD files as well.

I would however like to add that you can also try splitting off the weird geo and try to retopologize it using one of the new retopo generators that are there in the newer Cinema 4D releases. Sometimes that can help. Sometimes. :))


I totally agree, the new Zremesher works like magic for these broken models. I used to retopo some models I get from furniture manufacturers. But now with the Zremesher, sometimes I don't even do anything else. It does the retopo with only quads, loops, quite a game changer in my opinion.

2022-08-18, 11:18:42
Reply #12

pokoy

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Not sure but I think no one mentioned yet that for CAD meshes (which should have explicit normals if the export/import went through fine) you need to set shadow terminator to 1.0 (advanced dev settings / play with values above 0.5) otherwise shading and normal artifacts are unavoidable, unfortunately.