How to extrude a one-sided polygon object for printing?
Posted: 30 November 2019 04:14 PM   [ Ignore ]  
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I created a model of a low-poly house and prepared a UV map texture. I next wanted to extrude the polygon sides to give the walls sufficient thickness so it can be printed in color. However, somehow in the modeling some of the normals got flipped, so that when I try a global extrude, some polygons - particularly in the ceiling of the side porch area - extrude in opposite directions and defeat the operation. I tried flipping normals, aligning normals, splitting the polygons (so as not to affect the texture map) then doing a global align normals on the new mesh - nothing worked. MoExtrude seems to handle the extrusion part all in the same direction, but it screws up the texture map.

Model here (MIME error again)
https://adobe.ly/2DJp74F

I’ve reviewed several tutorials that demonstrate sure-fire methods for prepping a single-layer polygon models for printing (adding cloth or volume builder) but these add artifacts, and I’d prefer to keep the low polygon count and simple construction instead of adding a lot of new geometry.

I think if the normals could be forced into alignment some way, the standard extrude would work fine.

Any pointers would be appreciated.

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Posted: 30 November 2019 07:46 PM   [ Ignore ]   [ # 1 ]  
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Hi mford610,

The model looks like it is based on double-sided polygons. In other words, each polygon is twice in the scene. When I opened it, it had 1897 Polygons, after the steps mentioned below, it came down to 862.

Select all points, the use the Mesh> Remove> Optimize Command.

After that, the Mesh> Normals> Align Normals, and Reverse Normals.

I tested Cloth with zero subdivision and thickness to -1. Already there, the window of the side porch intersect, which means, the extrusion needs to be done in several steps. If it is for 3d printing (your post isn’t clear about this, then you might flatten that window. There might be more details to master, but I don’t know the needed dimensions for the targeted dimensions. Your model is ~7mx10m.

Let me know if you have other questions about it, I’m happy to look into it.

As a side note, simple options for add thickness to a model might create overlapping sections. Hence the problems.

Check your Cineversity-Private-Messages.

All the best

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Posted: 01 December 2019 07:06 AM   [ Ignore ]   [ # 2 ]  
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Ah! I see what you mean. That’s crazy! Once the duplicates were removed, it appeared that each polygon on the face was flipped opposite from the polygon next to it. Like a patchwork quilt! Two questions - one, can you divine how I might have duplicated all the polygons to start with? And two, how would each polygon flip in that precise pattern?

For background. I started with a cube, made it editable, then proceeded with the loop knife to cut the window vertices and extrude the panels. Very basic operation. Seems weird that I could make such a profound mess of it.

Maybe I split polygons at some point along the way without realizing what I was doing (that almost never happens).

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Posted: 01 December 2019 09:15 AM   [ Ignore ]   [ # 3 ]  
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That would be a wild guess, and I have no idea how I would create this in a repeatable fashion.
I can only imagine that a single control-click with a short movement, while perhaps Snapping was enabled, has created a duplicate.
Form there any step was maybe based on selecting more than what you thought you select, and hence the resulting mystery.
Again, that would be a wild guess.

BTW, I was curious about what the best way would be to give the house some walls. So far, I created the roof and the floor, to close the “volume”. Then I created an L shape Spline and extruded it. This extrusion was then subtracted from the house.

Cheers

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
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Posted: 14 December 2019 07:34 AM   [ Ignore ]   [ # 4 ]  
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Per your advice I was able to consolidate and extrude the house in several sections, and finally got a model that Shapeways liked. OBJ and DAE exports came in fine and were printable. The scale is wacky, but I am able to resize in Shapeways to about 6 inches, and everything looks fine.

The problem shows up when I export for color printing - using VRML 2, which is their preferred format. Now I get a non-manifold error, which I understand to mean the object doesn’t enclose a volume that can be printed. I tried uploading OBJ and DAE versions with the textures, but those failed to upload (no error given). There’s no one to ask about this at Shapeways other than the forum - which is too confusing to contemplate.

So while this is a little out of Cineversity’s lane, I know that in the past you have been able to analyze my geometry and find huge glaring mistakes that I did not recognize. So I’m wondering if you can check out these two models and see what might be going on that would generate a non-manifold error in one format but not another? As you pointed out earlier, I did some weird modeling that resulted in some odd behaviors, so I’m hoping you can spot the deficit one more time smile

Files are here: https://adobe.ly/2YKR6un

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Posted: 14 December 2019 11:17 AM   [ Ignore ]   [ # 5 ]  
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Hi mfrod610,

Please go to the Attribute Manager> Mode> Modeling. Select Bad Polygons. While only the bad stuff is selected, delete. Use the Optimize function after that.

Run the Bake Object (Shift +C).

Export via VRML 2 (no animation). Set the texture to 4K (I had trouble with 8K, size-wise [MB]) Zip it and ready for upload.

I have done this for you and checked the geometry with Shapeways. No problems. I’m not sure if the colors are in the preview as well.

Check with them carefully, and to make sure: no guarantees from my side for anything printing, or related. Check with the company that your product will be as expected.

Your file and a screenshot
https://www.amazon.com/clouddrive/share/sLO3XUH1F5vubKt3nI9TfEdhc3C6DIl7b172Ulq2iRm

My best wishes for your project

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
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Posted: 14 December 2019 07:33 PM   [ Ignore ]   [ # 6 ]  
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Ah, of course. Bad polygons. You fixed that once before - should have remembered. Thank you!

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Posted: 14 December 2019 08:27 PM   [ Ignore ]   [ # 7 ]  
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You’re very welcome, mford610, thanks for the reply.

I have not tried to upload it to the printing company as I have received it. Checking the mesh, then baking all textures into one, while setting up the UV, so no overlapping happens. I’m not clear how much complexity those companies allow. So far, I have sent to this company dense meshes as well as simple ones, but never anything that was a collection of things.

If you get it back, I would love to see an image of the result, if you have the time to snap one.

My best wishes for this project!

Cheers

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
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