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Clean Geometry from an Extrude Nurbs
Posted: 01 November 2019 04:27 PM   [ Ignore ]  
Total Posts:  434
Joined  2012-01-05

Hello

I have spline that is just a rectangle being extruded by an Extrude Generator.
I want to convert it to a polygon surface to create a cloth simulation.  However I notice that even if I select “quadrangles” and “regular grid” in the Caps of the Extrude, I still get non-optimal geometry.
If I leave at N-Gons and then try to subdivide after converting to polygons, I still get bad topology.
Is there a way to get something cleaner from an Extrude?

Thanks!

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Posted: 01 November 2019 04:47 PM   [ Ignore ]   [ # 1 ]  
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Hi Alex,

Please have a look here
https://www.amazon.com/clouddrive/share/xd2SYDTOCzXuLjxE1k7IELYFzozEf5vTnIumQ6Xbdp5

There is a dependency of parameters to get a clean model. The spline has 7 intermedia Points. This works along with the setting Natural or Uniform, etc.

If set right, and the responding parameters in the Extrude fit, you get a clean mesh. Well, that sounds easy with a Rectangle, but more often than not, it is tricky.

You could also create a flat polygon, with the mesh you need, and then use the Extrude with the function> Create Caps: on and the mesh should be fine.

The project file and screenshot
https://www.amazon.com/clouddrive/share/BfZZzoFPvIrBTIZhOC3WOcuL5CmAhvNiJ8c4jgWeyMV

Extrude only one time with the Create Caps on! Otherwise, you will run into problems with the Subdivision Surface.

Let me know if there is anything else, perhaps with a project file.

Cheers

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Dr. Sassi V. Sassmannshausen Ph.D.
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Posted: 01 November 2019 05:41 PM   [ Ignore ]   [ # 2 ]  
Total Posts:  434
Joined  2012-01-05

Thanks Sassi, so yes I probably need to be more specific.
Here is a project file
https://www.dropbox.com/s/unl1k986t4psgzr/ExtrudeClean_Question.c4d?dl=0

This is the context : in After Effects I have a composition (13725x1080) that I have an animation on.  I then need to bring this animation into C4d and put a cloth animation on it so it seems like my animation was in fact happening on a curtain.  It is a sort of transition “trick”.

I noticed that in Cinema, if I create a project with the right dimensions(13725x1080) and try to put a plane exactly where the camera frustrum edges are, I still get some slight mismatch with the AE comp.

So what I did is make a dummy comp in AE with a single 3d shape layer at the right dimensions.  I then export this to C4d, and what I get is a camera and polygon size/placement that perfectly match AE.
But…the problem is that the Shape layer comes in as an extrude object

Now I figured something out that solves the whole thing for me..If I export a Solidy layer from AE rather than a Shape layer, I in fact get a plane object…So it is much easier to work with.

Thanks!!

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Posted: 01 November 2019 06:19 PM   [ Ignore ]   [ # 3 ]  
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Hi Alex,

The relationship between the camera’s angle of view and its distance is precise. I have no idea why you have trouble. The default camera setting gives the distance in Z based to the object; the distance is the width of the object.
With a camera setting of 50mm (36mm sensor), this object width (focal-plane) needs to be divided by 0.72 to get the z-distance.  The numbers that come from Ae confirm this math as well.

In your scene file, the Extrude goes with its caps 20cm more in-depth, which might be not really relevant, but worth mentioning, speaking of precision.

Since the 13725 and 1080 have no usable “Lowest Common Divisor” (which would deliver a size for the quads), I would suggest to set up a Plane in that size set to Z- and 343 segments to 27 segments. If you need to extrude this, use the Extrude command.
Example
https://www.amazon.com/clouddrive/share/to0OjAsZJiYIcTNo6plZcoqZRCTtlLYrYz2UhXg6Me8

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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Posted: 01 November 2019 07:37 PM   [ Ignore ]   [ # 4 ]  
Total Posts:  434
Joined  2012-01-05

Hey Sassi

Thanks for this!
So where do you get the Object width divided by 0.72?  That is a handy thing to know ....

Thanks!

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Posted: 01 November 2019 08:23 PM   [ Ignore ]   [ # 5 ]  
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Alex,

For my panorama shootings, I have often to calculate the field of view of any lens (I have a lot of lenses, it’s not just the standard set), so this is pretty similar to what I do practically.

For your convenience, I have set up a little Xpresso here
https://www.amazon.com/clouddrive/share/SuSMNHvceDqJEON5KuU9U0sv21sJFdWjqESMbiM0vOl
It is based on the horizontal field of view.

The screen capture shows this tool in action.
I have added after the recording the factor value to the User Data, just in case.

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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Posted: 01 November 2019 10:00 PM   [ Ignore ]   [ # 6 ]  
Total Posts:  434
Joined  2012-01-05

I can’t tell you how extremely useful this is!  Super powerful…
Thanks so much for sharing, I know it will come in handy more than once.

Thanks Sassi!

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Posted: 01 November 2019 10:17 PM   [ Ignore ]   [ # 7 ]  
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You’re very welcome, Alex; thanks for the feedback.

I have set this up for you, if you need any changes, please let me know.

Here is one with a calculation UI (klick on the Xpresso Tag> Attribute Manager)
https://www.amazon.com/clouddrive/share/OMDqVVVvEjdKAB2XV4unLF3xlFd7jrMKwJf2uocN0cF
Set the “Sensor Size” if needed in the camera.

BTW, practical lenses often do not have a precise measurement of their focal length. I have seen often derivations from around +/- 10%, and with some even more.

Cheers

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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