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FSXA So why is this happening?

F747fly

F747fly

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I found a weird bug in my Blender 3d model today, when using the "subdivision suface"-modifier to smoothen the model this happens near the nose...

a350%20XWB.blend_zpssprlnuwu.png


can anyone explain to me what this is and why it is happening? Or (if necessary) what other modifier(s) I should use to make a smooth surface...
 
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I don't use blender, so I'm sorry if my response is not helpful. I base this on the possibility that subdivision mesh issues are similar between blender and 3dsmax. When this happens in 3dsmax, its caused by a flaw in the underlying topography. Normally, when you investigate closely you find that your edges form triangles where the burbles are. Subdivision can't do a good job with triangles, it needs quads.

The other possibility is that the edges are not continuous, like you need to weld some verts, but I'd put my money on you finding some triangles.

Show us a wireframe version of this image, it will probably be obvious.
 
F747fly said:
I found a weird bug in my Blender 3d model today, when using the "subdivision suface"-modifier to smoothen the model this happens near the nose...
can anyone explain to me what this is and why it is happening? Or (if necessary) what other modifier(s) I should use to make a smooth surface...
Click to expand...

Hi F747fly!

Yes, I would say that what Bob5568 told you is the reason for the faces being messed up. I use Blender, and every time I have seen this problem is when I tried to use the Boolean operation and it used triangles. I do not use the Boolean operation any more just because of this reason. Also you will run into a problem using subsurface modifiers if you use triangles. Try to only use quads when making your models.

Thanks, Kris:)
 
I'll actually have to see if I have triagles (if so it's unintentionally). I did use booleans but would that mean I can't use the model at all? Or do I have to do something special to smoothen it after all?
 
If you have triangles, then you must re-topologize that section. If you could undo that boolean, that's be great. Then, instead of boolean, manually design the two sections to have matching edges, meaning having the same position and quantity of longitudenal edges. In max, we would use an "attach" command to make the two parts be seen by max as all one part. Then you can weld the vertices at the join.

If you can't undo your work, you'll want to delete the messy section of the mesh and rebuild it. Make sure you have the same number of longitudenal edges in both sections. Then you attach the sections and weld the co-incident verts.

I'd bet you'll never succeed with subdivision smoothing if you use boolean. Get in the habit, if you plan to use subdivision, to insist on manual control of your mesh.
 
Okay. Just two things I'd like to ask then...

First, does this effect only happen in areas where the triangles are?

And second, if I can just remove the triangles (they probably are just squares witch turned into triangles) and turn them into squares, would that fix this problem?
 
Almost yes and yes.

The only other area I've seen imperfection is when a quad is not a "proper quad". If you imagine a triangle, but because you added an edge leaving one leg of the tri, you can claim it as a quad. That will often burble also.

I have to believe the process I suggested will be faster, but if you want to edit the mess that boolean provided you, that should work.

The underlying logic is worth understanding. Subdivision takes each polygon and splits it horizontally and vertically. A single quad becomes four quads. So, try to imagine applying that logic to a triangle? Its amazing our design tools don't crash.
 
Heres a pic, always easier to see. Each image on the top row is the starting mesh. Below each item, the copy has subdivision smoothing (in 3ds lingo, the modifier applied is turbosmooth) applied. On the left is a quad. In the middle two triangles. On the right is an "improper quad" attached to two proper quads.
 

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Thanks! I got all the triangles out and now it looks way better!

a350%20XWB2.blend_zpsqfixgan6.png


Although I should clean it up a bit more to get those lines near the windows removed... ;)
 
I must say subdivision looks verry good on the wings! :) (if I say so myself)

a350%20XWB.blend3_zpshcuaj1d1.png


follow up question would be, if using a sudivision of 6, would adjustments to the wing and such still be possible after pressing apply?
 
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Okay, now comes the following problem... I've modeled the wings to work with a dubdivision of 6 (they look best that way) meaning that without the subdivision they look very odd... That means I can't cut out the aerlerons etc. before I subdivide (it won't match) but I also can't cut them out after the subdivion, there're too many verteces after that... any ideas?
 
I would always make adjustments on the original topography, not the subdivided topography. Maxxers have a way to show both, letting you work on the low poly mesh while seeing the results right away. Not sure if you can do that.


In 3dsmax, I would define the edge of any thing that will be seperated from the main mesh when creating the initial topography before subdivision. Then you would use a command in max called "split", which makes the aeleron mesh subdivide separately from the rest of the wing. Then when you apply turbosmooth, you'd apply edge loops to perfect the gap between parts.

We also have a control called open subdivision, which has procedural controls over the edge crease, so you don't have to use edge loops.

THere are many ways to skin a cat...I'm sure people do this many ways, but I don't know anyone that would attempt to create cut outs after subdivision.
 
Okay... Seems like a good way, however the deforming is a bit confusing... I was fiddling around a bit more with it, when I get subdivision 3, then cut, select all wing parts and subvidive 3 again it works... Witch is a bit weird but if it works... :)
 
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