2 rail sweep problem

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 From:  Wts (ALEXANDR)
5046.1 
Hello! How can I fix this?
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 From:  bemfarmer
5046.2 In reply to 5046.1 
The experts would probably like to see your actual .3dm model please.

Edit, deleted poor attachment.

EDITED: 3 Apr 2012 by BEMFARMER


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 From:  Michael Gibson
5046.3 In reply to 5046.1 
Hi Alexandr, yes please post your 3DM model file with those curves in it so that I can examine the actual geometry.

It looks like possibly your profile curve may be kind of slanted instead of perpendicular to the rails or something like that? It's difficult to tell what is going on just looking at a screenshot though since I cannot rotate a screenshot or zoom in or things like that which I can do with a 3DM file, that's why it helps a lot to post the 3DM model file with your geometry in it.

- Michael
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 From:  Wts (ALEXANDR)
5046.4 In reply to 5046.3 
Hi Michael! Thanks for you reply. Here is 3DM file.
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 From:  Michael Gibson
5046.5 In reply to 5046.4 
Hi Alexandr, there are a few issues with the shaping of your curves, notice from the front view these little extra poking out pieces:



Those are sticking out because the curves are kind of hooked and bend inwards sort of like this:






I've attached a 3DM file that has some of that tuned up, but it's still problematic to try and use Sweep for it due to the fairly large flat areas that you have at the ends of the sweep.

For things that have big flat areas like that with blending between them, it tends to be better to model the flat areas first and then use fillet to put in the blended parts rather than trying to do a multi-blending type shape all in one single go with sweep like you are trying to do here.

The fillet method would go more like this - start with a narrow box:



Then select these edges:



And fillet them with a larger radius value to get this result:



Now select these edges:



And fillet them with a somewhat smaller radius than was used for the previous one, to get this:



Is that the kind of shape that you are trying to build?

It tends to be difficult to control surfacing commands like sweep when you are trying to put in multiple bended areas in the sweep all in one shot, it tends to be better to make sweeps be more one broad shape and if there are any tighter bends in it the tighter bends are usually better to do as fillets.

- Michael

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 From:  bemfarmer
5046.6 
Network seemed to give a fairly good result.
Did not check out the little "defects."
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 From:  Wts (ALEXANDR)
5046.7 
O, thanks for your explanation Michael! NURBS modeling is very unusual to me. I tried to model this thing via Construct > Network, but there some "defects" like bemfarmer said. Maybe there is special method to model things like this (it's mobile router back cap)? I can do this thnig in XSI (my primary package) with poly modeling, but I want give MOI a try. I attached 3dm file with "defects", and photo of this evil object :) Many thanks for your help guys!
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 From:  Michael Gibson
5046.8 In reply to 5046.7 
Hi Alexandr,

> Maybe there is special method to model things like this
> (it's mobile router back cap)?

Well like I wrote above, it's generally better to model things like this by using fillets to blend between some primary surfaces rather than trying to directly shape the blended areas all in one shot by either sweep or network.

When you see a broad flat-ish area, that should generally be modeled as one surface itself, then when you've got a tighter bent region between 2 of those flat-ish areas, use fillets to put those in.

Otherwise it can be difficult to control surface construction when you've got a lot of variation in shape happening in the profile curves. Basically when you have a profile shape that goes through some kind of tight bends in it, you're trying to squeeze a couple of shapes out of it instead of one broad shape and you can easily run into issues about how different pieces are being matched with one another, and stuff with pinching and squashing of shapes as they try to transition from one to the other across your single surface.

See these previous posts for some more examples of this kind of shape construction:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1002.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=3137.1


Also here are some other examples of that general strategy of building some broader sheets of a model out of sweeps and then having a fillet provide a smooth juncture between them:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2164.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=2164.4


Also Check out here for some links to previous discussions with some various tips for people coming from a poly modeling background:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

- Michael
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 From:  BurrMan
5046.9 In reply to 5046.8 
You are trying to model multiple parts with one command.

Looking at the pictures you posted, the side view would show 3 distinct shapes. It might look a little more like this:

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 From:  Frenchy Pilou (PILOU)
5046.10 In reply to 5046.9 
Cool little tutorial object and magic Blend function!
---
Pilou
Is beautiful that please without concept!
My Gallery
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 From:  Rich_Art
5046.11 In reply to 5046.10 
2nd that...

Peace,
Rich_Art. ;-)

| C4DLounge.eu | Our Dutch/Belgium C4D forum. |
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 From:  bisenberger
5046.12 In reply to 5046.9 
Hi Burrman,
I tried watching you video, but it said it was private.
Bill
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 From:  BurrMan
5046.13 In reply to 5046.12 
Hey Bill,
Google seems to be randomly changing some settings. You should be able to see it now.
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 From:  bisenberger
5046.14 In reply to 5046.13 
Yep, that did it!
Thanks Burrman
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 From:  abe
5046.15 In reply to 5046.9 
Hi Burrman, that's a cool video but I have a problem at the very beginning. My initial curve is a filleted rectangle and is composed of 8 joined segments, therefore the extrusion has eight seams instead of one. I can't see a command that'll merge the curve segments into one before doing the extrusion. Is there such a command or do I have to draw the initial curve by hand?
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 From:  BurrMan
5046.16 In reply to 5046.15 
Hi Abe,
Select your object and hit Tab and type Rebuild.
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 From:  abe
5046.17 In reply to 5046.16 
Thanks for the quick reply! Unfortunately, Rebuild only creates an approximation to my G3 filleted rectangle. Further, the rebuilt curve's seam was not on the long axis axis of symmetry, unlike the example in your video. I can use Loft instead of Extrude to position the seam of an 'extrusion', but I don't want to be working with a rebuilt approximation to my curve. I guess I need to draw my filleted rectangle by plotting control points if Moi has no way to simply merge curve segments. Also, is there no way to merge surfaces?
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 From:  Michael Gibson
5046.18 In reply to 5046.17 
Hi abe, there is not currently any way to merge curve segments to one another without some adjustment like Rebuild or deleting the control point where 2 segments touch. There is also no way to merge surfaces currently either.

I want to add in methods for both of those, but I have not quite figured out where to put that functionality in the UI yet.

- Michael
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 From:  abe
5046.19 In reply to 5046.18 
Thanks, Michael. I look forward to that and will continue to enjoy your software as it is in the meantime. :)
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