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Black shadow/edge/outlines problem with bump and displacement

15 REPLIES 15
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Message 1 of 16
nfavereaux
1386 Views, 15 Replies

Black shadow/edge/outlines problem with bump and displacement

Hi,

I have a problem sometimes with Arnold on Cinema 4D.

When i'm using bump, i'm getting black edges/outlines on geometry with Displace.

capture-decran-2020-11-11-130705.png


I've got a floor using a displacement map and arnold tag.

Whatever is the setting i use in subdiv and displacement the problem is still here.

The only thing that makes it disappear is cutting off the bump or put it to 0


Here is a screen with bump on with 0.001 cm :

capture-decran-2020-11-11-131053.png


Without bump :

capture-decran-2020-11-11-131150.png


My bump is a layer RBGA that mixes 2 C4D Noises.

I Tried to plug only one C4D Noise directly, same problem. Same thing with an arnold noise.

I already had this problem on a pyramid without any displacement and other occasions. My bump is always problematic. Same problem if i use a texture image for bump or even a normal map ...

My only temporary solution is to bake my displace into geometry. When i'm doing this the problem is almost invisible, i can see it in some occasions but i can't find a real solution.


Thank you in advance.




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15 REPLIES 15
Message 2 of 16

Hey,

I've had this one in the past.

I found that sometimes when applying bump to low poly objects. You can get artefacts similar to what you have, show up on the glancing angles/edges of the geo. I think the normals might be getting a bit screwed.

I could totally be wrong, but maybe try bumping up the object's subdivs a little and see what you get. It might be worth a shot, as the object looks a little low poly at the moment.

1605109711894.png
I think you can a similar result from having the bump too high, though I don't think it will be that this time around having seen you're screenshots.


Message 3 of 16
nfavereaux
in reply to: nfavereaux

Hi,

Thank you for trying to help 🙂

Unfortunately whatever level of subdivision i put in the arnold tag, the problem persists ...

Message 4 of 16

Sorry, I meant the actual objects geometry subdivisions.
Opposed to the rendertime subdivs 🙂

Message 5 of 16
lee_griggs
in reply to: nfavereaux

Does it happen if you apply the shader to a different object? Can you upload a simplified scene somewhere?

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 6 of 16
nfavereaux
in reply to: nfavereaux

Connor,

I tried to increase by 4 the level of subdivision of my mesh, directly on the geometry, the black shades are less visible but there's a lot more of them ...capture-decran-2020-11-11-185701.png


Hi Lee,

Thank you for joining the help !

Here's my file, this is just my plane with my shader and the texture for the displace.

https://drive.google.com/file/d/1H9-IkHpbvOK9c5uAEQuJ_B1ucjaBXKn7/view?usp=sharing

I tried to put the texture on the puppet model (without the displace) and yes the problem appears on it.


Thx !

Message 7 of 16
lee_griggs
in reply to: nfavereaux

Hi, nothing renders. Can you just assign the shader without texture maps to a sphere, please?

1605167427817.png

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 8 of 16
nfavereaux
in reply to: nfavereaux

Hi Lee,


Here is my shader on a sphere without the displace, i can see the problem if my sphere is low subdivided but it's very subtil. It's really obvious when the displacement map is on.


PROBLEM_BUMP_ARNOLD.zip

Message 9 of 16
nfavereaux
in reply to: nfavereaux

Hi,

Lee, by any chance did you have time to take a look at the shader ?

I'm sorry, i'm out of solution for this problem ...

Message 10 of 16
lee_griggs
in reply to: nfavereaux

Peter reported it to the team yesterday. There is a ticket for it now. Thanks for reporting Nicolas!

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 11 of 16
nfavereaux
in reply to: lee_griggs

That's great thank you very much.

Message 12 of 16

Thanks for the scene Nicolas, we're looking into it.

Message 13 of 16
sharmabhuwan14
in reply to: nfavereaux

Try disabling autobump in the displacement shader.

Message 14 of 16
nfavereaux
in reply to: nfavereaux

Hi Bhuwan,

The autobump is already off 😕

But thx for trying to help me !

Message 15 of 16
lionlion44
in reply to: nfavereaux

Hey I know this is old but thought I would post a solution I found for my scene. Quite weird but hey, it worked.


I'm doing this using houdini but hopefully the same nodes exist in Maya.


First get two 'state vector' nodes. One set to 'smoothed normal (no bump)' and the other set to 'ray direction'.


Plug these 'state vector' nodes into a 'dot' node. This will output a dot product between the smoothed surface normals and the direction of the ray coming from the camera. You should see values of -1 on surfaces that face the camera and values of 0 or more at the glancing edges of the object. (If its over 0 that means the normal and the camera ray are facing the same way. This is what causes the black edges in the original render)


Plug the 'dot' node into a 'range' node. Set the 'input min' to -0.1 and 'input max' to 0, then set 'output min' to 1 and 'output max' to 0. Then plug the 'range' into a 'clamp' node to clamp the output between 0 and 1. This should create a mask that has values of 1 at the problem areas (where the surface thinks it is facing away from the camera)


Then plug the 'clamp' into the 'bump height' input of the 'bump2d' node. This should cause the bump to turn off in the problem areas which hopefully won't effect the look of the bump other than removing the edge artifact :).


You can change the 'output min' on the 'range' node if you want to make the bump height smaller.


Hope this helps out for Maya folks.

2022-08-1915.43.462302320086957448401.jpg

Message 16 of 16
diego6S3FN
in reply to: lionlion44

This solution worked for me in this case but I had to put a negative value in the Output min of the range. Thank you!

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