Chaos Corona Forum

Chaos Corona for Cinema 4D => [C4D] Bug Reporting => [C4D] Resolved Bugs => Topic started by: atin on 2018-01-06, 12:42:08

Title: strange Polygon Lines / Edge-Shadow Problem
Post by: atin on 2018-01-06, 12:42:08
Hi,

I use C4D R17 and have this strange Lines and different reflections. All should be the same.... With Maxwell or C4D Render everything works fine. Please help, is it my fault or a bug?
Everything of the arm holder has a black material assigned, except the tip, the tip is silver.

See attachments please.

Using the latest Corona Beta Version.
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-08, 12:46:46
Hi,

I am sorry, but I don't see any lines that I wouldn't expect to see. Could you describe in a better way, what the problem is? A less noisy image would help too.

Thank you
Title: Re: strange Polygon Lines
Post by: burnin on 2018-01-08, 14:24:06
it's about how corona for c4d handles shading (normals, ngons...)
play with phong tag or set sharp edges or set normals or make extra edge loops or ... make a test scene & post it here

IDK, if it's a bug per se or something missing in the implementation or a technical limitation, since from what i've seen around different engines handles shading differently, some show no issue while others show a total mess (and user needs to correct the model)

also, by the looks of it, Max Corona seem to handle this just fine
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-09, 12:46:36
Hello, thanks for the answer.

The problem I mean exactly is, that the reflection is an other strenghth on the left side of the front armrest than on the right side. If you look at picture one (the unrendered picture), you'll see different green lines crossing the frontside of the armrest-model. The left reflection of the material (picture 2, short rendered, noise is not relevant here to explain the problem because it is so obviously) is more reflective and brighter than the right side. One line ist "cutting" the material but it should be just all the same. This is only with corona the case, with other rendering engines there is just one reflective material-style all over the whole armrest - how I wish it should be. I dont want this "reflective" cut.

Title: Re: strange Polygon Lines
Post by: houska on 2018-01-09, 13:24:25
Thanks for the clarification, now I understand!

Sorry for my confusion, but without the scene, it's hard to guess what should be the correct look. I actually thought that the right side of the armrest has a different material or a different normal, so I didn't think this is the problem that you're talking about...

Could you send us the scene with the armrest so that we can look at it? Just the armrest model will be enough so that you don't have to send the whole scene.

Also, for your information, there is a known bug with shadow terminator handling on geometry with assigned (as opposed to calculated) normals, which often happens for objects imported from different modelling applications. The bug manifested with similar artifacts for other people. The workaround for this is to disable the terminator handling in development settings (see the attached picture). Let me just stress here that development settings shouldn't be tweaked unless you know exactly what you're doing.
Title: Re: strange Polygon Lines
Post by: burnin on 2018-01-09, 16:46:51
Just a note...about Max users having similar issue > thread "Incorrect shading on imported geometry" (https://forum.corona-renderer.com/index.php?topic=18814.msg117740#msg117740), for anyone wanting to know more...
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-09, 18:15:22
Okay, so it is C4D corona issue, thanks. It seems I can't continue working that scene with corona :((((((

Note: The armrest is NOT importet, it is complete self - modelled.

I will post Scene in a few days when I will be back at workplace...
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-10, 13:32:55
Okay, so it is C4D corona issue, thanks. It seems I can't continue working that scene with corona :((((((

Note: The armrest is NOT importet, it is complete self - modelled.

I will post Scene in a few days when I will be back at workplace...

If it is the same issue as burnin reported, it's Corona issue, not Corona for C4D issue. And the issue could happen even if self-modelled. But then again, it could be a completely different problem. Thanks for willingness to share the scene!
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-10, 16:47:18
By the way, did you try to disable the terminator handling? And if so, did it help?
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-10, 19:15:51
What is this Terminator Handling? Where can I find it? Hearing it the first time in my life ^^
Title: Re: strange Polygon Lines
Post by: TomG on 2018-01-10, 19:26:22
In the Development/Experimental stuff tab:
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 10:42:18
Hi,

so in the attachment the scene. There is suddenly another issue, don't know why.  I can't start the render anymore, the whole c4d crashes until one frame is rendered, its not possible anymore to let the scene render at all.... black render screen -> c4d shuts down ;(

P.S. I don't have this tab in my redner setting, see "3"
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-11, 10:51:45
To enable the development tab, you have to check a checkbox in the global preferences. Let me warn you again that everything in the development tab is experimental and can change the rendering to the worse! Use with care ;-)
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 10:58:40
... still no terminator
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-11, 11:05:35
Ok, this is strange... Can you show me the output of the Corona -> About Window? We added the terminator handling UI a few weeks ago, so it should be there...

Regarding your scene, it renders fine for me, see the attached image
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 11:11:29
Sorry I installed an older version last time I was here at my workplace, thats why it crashes now, It was just my fault. Could you send me the link to the actual version I should use, please? Then I will try terminator...

Title: Re: strange Polygon Lines
Post by: houska on 2018-01-11, 11:16:30
The link is in this forum thread: https://forum.corona-renderer.com/index.php?topic=18711.0

The link itself (you'll want rc2): https://drive.google.com/drive/folders/1rUctswGPIeucE9JtjdQrzY3JZq67HNgw
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 11:17:26
Thanks!

I dont want to be picky, but look at screenshot 5, I think in the back of your render, the same issue appears I think...
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 11:29:16
Issue is still there when you rotate camera ("6"), from the position you rendered it looks good in my scene, too.
Phong Tag (+ a bit of terminator) assigned gives a bit of medicine but it is still not good. ("7")
Title: Re: strange Polygon Lines
Post by: houska on 2018-01-11, 11:34:19
You're right... I inspected the model a little bit more and the problem is that your geometry is not perfectly coplanar, so artifacts can appear, exactly as they would in real life...

I suspect that in your HDRI map (which cannot be extracted rom the .rar by the way), you have a sun, which is hit only by some polys, depending on their normal. This is why some of the polys of the geometry are lighter than others. You should fix your geometry.
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 11:42:19
Oh man, 3D is just  its own science ^^
Sometimes I think about getting back to oil paintings
Title: Re: strange Polygon Lines
Post by: atin on 2018-01-11, 14:03:10
So I have another Problem with this issue, on "L1" you see a round modelled Leg, modelled in Zbrush , maxwell and C4d rednder have no issues. When I render it in Corona, it looks like a very hard edgy "reflective" cute that crosses the model.

Please help, I love the render engine, but it seems not usable at this point to me, but mybe its my fault.

"L3" is with reflection turned complete off, so its not a reflective issue. The Bump Map covers everything perfect.
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: houska on 2018-01-11, 15:35:44
That is again pretty strange. Could we see the scene again? :-)
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: atin on 2018-01-11, 15:44:45
Sure, here, reflection is still unticked in material editor. Thank you!

PC: I7 3770, 64bit, Win 7 Pro
C4D: 17.016
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: houska on 2018-01-11, 16:31:57
You have unnecessarrily complex lighting setup there. Just remove all the cuboids with light materials and you should be fine...
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: atin on 2018-01-11, 16:50:16
Okay it was the outside of the airplane light, don't know why. Now I have 4 Lights left, i want to have this, like a kind of product-photo studio setup...

Without the outside box it works now.
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: Eddoron on 2018-01-11, 23:18:54
The armrest didn't have a phong tag, just adding one with standard 40°  settings solved that.(i also broke the ngons and reconnected the broken phong edges)
It was not a corona issue because the artifacts were visible in the editor window and standard render.
But as Houska mentioned, the polygons are not perfectly coplanar and some are hidden under n-gons.
Selecting a few of the points and decreasing the aberration in distance can solve that too.
Also, when not working with quads, be careful with bevel tools.
I'd advise you to create the armrests through SubD modeling. That should go really quick as you only need a few cuts and it keeps the mesh clean.

As for the leg...it looks like a (uv-)mapping problem(eg: a seam) but it could be anything. Can't tell without inspection.

edit: oversaw the leg scene. disabling the 2 side cube lights solved it. But the model didn't have any UVs. Since it was created in Zbrush, you can easily do that with UV Master. Just make sure, the seams are in positions where they won't be visible.

edit2: i obviously didn't read clearly, that some issues were already solved. So just disregard the most but look at what I wrote about topology&UVs.
Title: Re: strange Polygon Lines / Edge-Shadow Problem
Post by: atin on 2018-01-12, 11:12:50
Thank you all very much (;

Have a nice wekend!