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Author Topic: Unwanted Shadows on One Side of Vertical Fin  (Read 4524 times)

actionary

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Unwanted Shadows on One Side of Vertical Fin
« on: October 28, 2016, 05:27:14 pm »

Hi all!

I model old Turkish-made aircraft for fun.

Nowadays I'm modeling an old flying-wing sailplane design, with an intent to import it to Outerra and make it flyable. I'd been going well for my standards, but today I ran into a problem that is driving me insane :)

There are weird shaped shadows on the inner sides of the two vertical-fins, although the outer sides are perfect (again, for my standards).

Here, you can see the shading on the inner side:


Here is the normal, outer side:


And this is a screenshot from blender render-view:


I can't really say that this is an Outerra-related problem, because I'm not a pro in modeling so I may well have made some modeling mistakes. The fin profile is NACA 4306, a somewhat complex profile to model for a hobbyist like me. However, having seen that the outer side renders fine in both Outerra and Blender, and having been unable to solve the problem no matter what I did, I felt that I should resort to the forum.

I'm using an AMD system with an HD7900 series GPU.

Thank you in advance.
« Last Edit: October 28, 2016, 05:32:14 pm by actionary »
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necro

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #1 on: October 28, 2016, 06:39:47 pm »

Its not an OT related problem. The problem are missing vertices. Could you post a screenshot of the wireframed mesh? Adding some loop cuts will solve the issue.
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actionary

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #2 on: October 28, 2016, 06:47:48 pm »

Here you are, sir. But please know that this mesh became the mess it is now (triangles and missing edges, etc.) after I used Blender's clean-up tools to solve the problem.  :-[

Do you think it is recoverable?
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actionary

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #3 on: October 28, 2016, 06:53:58 pm »

Wait, it's not that bad. Somehow Blender's wireframe view gave me that result, but shaded view tells another story:
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StrakanXJ

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #4 on: October 28, 2016, 07:14:54 pm »

try to eliminate any tris (faces with 3 edges/vertices) and make as many of them quadrangles (4 vertices/edges each). Also be sure faces aren't twisted which often happens if the face is too large. Add extra loops where needed. The Vertex limit is about 65,000 per model so you can add a few no worries.
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actionary

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #5 on: October 28, 2016, 07:17:29 pm »

Okay, thank you very much. You'll be informed about the results :)
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StrakanXJ

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #6 on: October 28, 2016, 07:46:01 pm »

no worries, happy to help :)
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KW71

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #7 on: October 28, 2016, 07:52:44 pm »

Hi!

Don't seem that you need extra loops in this case. The engine needs the mesh to be unwrapped in order to compute tangentspace correctly, even if you are not adding textures for now. Try a fast UV method for now  (like planar in Max). to see if that solves your problem (wich is very probably).

This is the same model; the one in the right have UV coordinates:

« Last Edit: October 28, 2016, 07:54:49 pm by KW71 »
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"A man who is contented with what he has done, will never become famous for what he will do".

necro

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #8 on: October 29, 2016, 03:23:44 am »

Beveling the edges could eliminate shading issues too. But in this case you will be right - this model was probably not unwrapped. I you have questions about unwrapping i could give you some limited hints, because i'm using blender too.
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actionary

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #9 on: October 29, 2016, 07:10:53 pm »

Hi!

Don't seem that you need extra loops in this case. The engine needs the mesh to be unwrapped in order to compute tangentspace correctly, even if you are not adding textures for now. Try a fast UV method for now  (like planar in Max). to see if that solves your problem (wich is very probably).


OMG, so you're saying I deleted my beautifully-modeled (for my standards) NACA 4306 fin profile and modeled a convex-profiled fin for nothing...  =|

Still, thank you very much. I'll remember to unwrap my meshes before importing in the future.


« Last Edit: October 29, 2016, 09:55:17 pm by actionary »
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KW71

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #10 on: October 29, 2016, 07:25:43 pm »

 ;)
Hi!

Don't seem that you need extra loops in this case. The engine needs the mesh to be unwrapped in order to compute tangentspace correctly, even if you are not adding textures for now. Try a fast UV method for now  (like planar in Max). to see if that solves your problem (wich is very probably).


OMG, so you're saying I deleted my beautifully-modeled (for my standards) NACA 4306 fin profile and modeled a concave-profiled fin for nothing...  =|

Still, thank you very much. I'll remember to unwrap my meshes before importing in the future.


...and have always a backup  ;)
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"A man who is contented with what he has done, will never become famous for what he will do".

StrakanXJ

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Re: Unwanted Shadows on One Side of Vertical Fin
« Reply #11 on: October 29, 2016, 09:16:35 pm »

Hi!

Don't seem that you need extra loops in this case. The engine needs the mesh to be unwrapped in order to compute tangentspace correctly, even if you are not adding textures for now. Try a fast UV method for now  (like planar in Max). to see if that solves your problem (wich is very probably).


OMG, so you're saying I deleted my beautifully-modeled (for my standards) NACA 4306 fin profile and modeled a concave-profiled fin for nothing...  =|

Still, thank you very much. I'll remember to unwrap my meshes before importing in the future.

Not exactly. The reason faces are quads in blender is because renderers tend to break those faces into triangles. Its a lot easier for a renderer to calculate a triangle from an quadrangle or equal sided shape than from another triangle.  When this simple conversion goes wrong in a tiny bit you get artifacts and it's good practise to try to minimize it. In this case however (sharp blades/edges) UV unwrapping is a neat trick...

Thanks :)
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