blend & planar sections

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 From:  simba
7036.1 
Hello,

I'd like to blend two aerodynamic shapes using blend + planar sections. I did the same (see picture) with similar shapes in the past and it worked fine but this particular version doesn't work for some reason. I assume it's related to the fact that the edge at the lower cut is broken into 3 lines at the very end.

How can I fix the problem?

S.
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 From:  Michael Gibson
7036.2 In reply to 7036.1 
Hi Simba, currently your shape there is a closed solid - but Blend likes to work off of unattached open edges so it knows for sure which surface it should blend to. When edges are joined between 2 surfaces it is ambiguous which of the 2 possible surfaces it will target.

So use Edit > Separate or delete the bottom end cap on the upper piece and delete the interior walls on the bottom piece and then you'll be able to do a blend as in the attached file.

But you will not get very good shaping at the front part since it is so elongated and also goes through a sudden change in shape in these areas here:




You may need to do the blend only up to this far on the bottom edges and then use some other means for filling in the remaining area:




- Michael

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 From:  Lordfox
7036.3 
Helo, is there a nice short video tutorial / demo? For PLANAR SECTIONS? Because I didn't get good results. And If I create a parallel-stroke between (e.g. in the middle) two existent planars, I didn't get a new planar-section ... so I'm confused. Ok, there was also a other thread about PLANAR SECTION, but I couldn't understand relly how it works, also is my english not the best. So a demo - would be cool.

p.s I did see the nice MULTIISO Script and a nice youtube tutorial von Mr. Andrew Samardac, but thats different!

EDITED: 10 May 2015 by LORDFOX

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 From:  Michael Gibson
7036.4 In reply to 7036.3 
Hi Lordfox, check out here for some description of planar sections blend:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6790.35

If you are still stuck with using it on your particular case, could you please post your 3DM model file so I can take a look at what you're trying to do?

- Michael
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 From:  Lordfox
7036.5 In reply to 7036.4 
Hello dear Michael, this is what I mean, I didn't see good results and I didn't see sections after using a parallel planar section between two planar sections ..
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 From:  Michael Gibson
7036.6 In reply to 7036.5 
Hi Lordfox, if you still need more information can you please post the 3DM model file where you didn't get good results so I can look at what you're trying to do there?

The "planar sections" option does not mean to use it between planar sections as the input edges, it means to make the blend create all planar curves for the cross sections that are used to calculate the Blend. Blend constructs a surface basically by lofting through a whole bunch of automatically constructed profile curves that attach between the 2 surfaces. When these profile curves wiggle around it can tend to make lumpy results in the blend. The "Planar sections" option tries to instead make each profile curve go on a single plane and that tends to make them wiggle less and can help avoid them from pushing through each other.

Usually it's used when connecting a closed tubular type surface like a wing shape onto a main body as shown in that previous example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6790.35

re:
> and I didn't see sections

That's normal that you won't see separate sections displayed - you will only see the Blend surface displayed. The planar sections option just modifies how the blend surface is constructed.

- Michael
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 From:  Lordfox
7036.7 
Hey, I'm sorry, maybe you can see, what I did made wrong. I did have made a small screencapture-video - it's just a question - HOW TO USE the PLANAR SECTION

http://www.mediafire.com/download/e6w3m98ex4y0k48/test-planar-sections.3dm

http://www.mediafire.com/watch/5q4xp8qs3016eic/Blend-Planar-Sections.avi
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 From:  Michael Gibson
7036.8 In reply to 7036.7 
Hi Lordfox, Blend in general, whether planar sections or not is just not going to work very well on a case like you have there because you've got such differently shaped things you are trying to blend between.

Planar sections will especially have problems if one of the curves does "back tracking" and does not form a convex shape, and also if the surfaces being blended between have surface normals pointing nearly opposite from one another.

I've attached here an example for where planar sections will help, choose the "up" direction for the planar sections to be along the tubular surface's direction, which is the world z axis direction.

But basically in order to get a good result your objects can't just be wildly dissimilar like your case is, they need to be somewhat more reasonably similarly structured.

- Michael
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 From:  Lordfox
7036.9 
Okay, thank you :) now I did understand it, so my shapes to different .. okay, I did think, that planar sections will create some morphs/blending between 2 very different shapes, similar like blending in illustrator. ;)

Did you have also a example for the SYNC POINT option?

Thank you so much ;)

I will try also the multiiso script and the lineweb script
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 From:  Michael Gibson
7036.10 In reply to 7036.9 
Hi Lordfox,

> Did you have also a example for the SYNC POINT option?

The sync points option allows you to control which spots of the edges will be connected together in the blend surface. By default the edges are matched by distance traveled along each edge, but sometimes it can be better to manually control how things match up.

Here's an example, since the bump in these surfaces are at different lengths along the edge, the default blend surface will sort of have 2 bumps in it like this:





That happens because the default connection between things is to just connect the same percentage distance traveled along each edge, which means the tip of one bump is connected to this spot on the other edge in this case:



You can manually control the connection by adding in sync points, for example adding in sync points in these 2 spots will make this result:




It basically allows you to manually control which areas of the edges will be synchronized with each other during the blend surface generation.

- Michael

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 From:  Mauro (M-DYNAMICS)
7036.11 In reply to 7036.10 
Thanks Michael...a good example :)
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 From:  Lordfox
7036.12 
yes, thank from me too, nice :)
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