Blender-made object shading horribly skewed

Started by N-drju, April 24, 2021, 02:02:20 pm

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N-drju

Hello Guys,

Currently, I struggle with a very strange glitch which causes one of my objects in Blender to look like this when viewing it in Blender:


saywut1.jpg

The object consists of many vertices and it is quite high-poly. It is completely smooth. Yet, lots of the faces within are simply being displayed with all possible shades of grey, giving an impression of a rough surface.


I would not mind that of course if this was just a display glitch with no influence on the actual render. Unfortunately, the object is being rendered incorrectly in Terragen. The shading near its curved edges is completely inacurate:

saywut2.jpg

I'm helpless really... I tried to clean up the object in Blender, recalculate normals, remove doubles (there are none anyway) etc. Nothing works. Please help me understand what is going on here.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

archonforest

Perhaps you want to upload the blend file? I can take a look.
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram, GTX 1080
Amiga 1200 8Mb ram, 8Gb ssd

N-drju

Quote from: archonforest on April 24, 2021, 02:15:10 pmPerhaps you want to upload the blend file? I can take a look.
Gladly, thank you for your offer Attila!

I'll have my dinner and will upload the file.
  ;)
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

N-drju

April 24, 2021, 03:50:17 pm #3 Last Edit: April 24, 2021, 03:53:57 pm by N-drju
Here it is. It's almost 100mb so I just offer a link to my Google Drive:

https://drive.google.com/file/d/1qMQf4IhYAj8yhgOB4ap4b4jovrmfmTNK/view?usp=sharing

Here is what I do in sequence and when the problem appears:

1. I create a 1.32 meter high and 0.01 meter wide plane object.

2. Then, I use the mirror modifier and translate the initial object to a desired spot.

3. Then, I subdivide the plane strip horizontally into about 750 edges.

4. I then grab the middle edge, pull it out and use inverse square profile to make a gentle curve...

5. ...after which I select one vertex line to spin the object to create a gently curving wall. This is were the object breaks apart.

I really wonder if you even see the object the same way like I do. In any case - do let me know about your findings.

I believe that this is some kind of a software problem and not hardware related - all of the objects created prior to this one load up and are displayed correctly.

EDIT: I just checked the object on my laptop and it looks just the same. Definitely not a hardware issue...
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

archonforest

My blender is crashing on the file at opening. I have only 2.79 right now on the laptop front of me. Tomorrow I will check on my workstation where I have the latest Blender.

Otherwise I am not sure why you make this "simple" looking object like the way you wrote. At least on the picture the object look very simple.
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram, GTX 1080
Amiga 1200 8Mb ram, 8Gb ssd

N-drju

Quote from: archonforest on April 24, 2021, 04:09:41 pmMy blender is crashing on the file at opening. I have only 2.79 right now on the laptop front of me. Tomorrow I will check on my workstation where I have the latest Blender.

Otherwise I am not sure why you make this "simple" looking object like the way you wrote. At least on the picture the object look very simple.
It's pretty large so maybe this is the reason why your laptop can't process it. I don't know its specs though.

I make it this way so I can create a symmetrical shape. Mirror modifier seems to be best to do it.

After some extra research myself, I can see that Blender seems to have problem resolving very thin objects. When the cable car's wall is about 10cm the problem doesn't seem to appear.

In any case, thanks again for your kind help. 
:)
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

archonforest

Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram, GTX 1080
Amiga 1200 8Mb ram, 8Gb ssd

N-drju

Hmmm... Now it starts to get really interesting...

I've tried several more primitives with various amounts of edges and curving and they all break down as soon as the "mirror" modifier is applied... Always. :o The hell is that?

Can you confirm that Attila? Make sure to try the 2.8 build.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

archonforest

I can do it tomorrow only. Otherwise in general I have no problem with the mirror modifier. I made few things with it but worked as it suppose to be.
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram, GTX 1080
Amiga 1200 8Mb ram, 8Gb ssd

KlausK

Hey there, can`t help you with Blender, really...but does this look any better to you? Rendered in TG.4.5.56.

CHeers, Klaus
/ ASUS WS Mainboard / Dual XEON E5-2640v3 / 64GB RAM / NVIDIA GeForce GTX 1070 TI / Win7 Ultimate

sboerner

April 25, 2021, 12:15:58 am #10 Last Edit: April 25, 2021, 12:21:05 am by sboerner
That's a really beautiful shape, N-drju. And as KlausK shows it should render just fine.

The edges that you are seeing in the Blender 3D window and in your TG rendering are caused by using too many polys. I know this sounds counterintuitive. But when you subdivide your model so early in the process, any small rounding error in subsequent warps and transforms may prevent some of those tiny polys from deforming smoothly. And once they're out of kilter it's impossible to fix them. It's much better to start with as few polys as possible, apply a subdivision modifier, then adjust the cage to achieve the shape you want. Then, when you're happy with it, bake the subdivisions.

IMHO the main shell in this object has many more polys than you need. Probably 10-12K would be fine. I know this isn't a Blender forum but I'd be happy to share an example file if you are interested.

N-drju

Thank you for your input @KlausK and @sboerner and for joining this discussion.

@KlausK - Yes, I think there is some improvement. But did you change something in particular? Either in Blender or TG?

@sboerner - Thank you for this information. That sounds reassuring. Perhaps I expect a little too much from Blender (and myself). I am a newbie to Blender really and I only did simple geometries (like houses) so far. I admit that there is a lot more to learn.

I presume this is indeed more of a Blender questions than TG one. My reasoning was that the object ends up in TG, so it doesn't really matter. :-X I look for solution in both TG and Blender after all.

Luckily, I remember that 1K+ users have the right to move topics to other sections, so I'll try it now.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"

sboerner

QuoteI presume this is indeed more of a Blender questions than TG one. My reasoning was that the object ends up in TG, so it doesn't really matter. :-X I look for solution in both TG and Blender after all.
You're right. We all use TG in combination with other programs, so your reasoning makes sense.  :)

Take a look at this. This was built using your shape as a guide. Modeled mesh is on the left, model with mirror and subdivision modifiers is on the right. Slightly more than 11K polys, *should* be enough for rendering in TG but I didn't test it.

This is done in Blender 2.92. You should upgrade! They've made some amazing improvements.

archonforest

Finally I manage to open your blend file. Holly molly! The polly count is insane for a model like this. Sboerner solved it correctly for you and the tips he wrote to you are 100 percent correct.
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram, GTX 1080
Amiga 1200 8Mb ram, 8Gb ssd

N-drju

Here's the first wall with just 8 horizontal and 8 vertical edges:

saywut3.jpg

I did not check how it looks in TG but... damn...

Any ideas? I checked my GPU and CPU - both healthy. I'm fresh out of ideas.
"This year - a factory of semiconductors. Next year - a factory of whole conductors!"