How to extrude a one-sided polygon object for printing?
Posted: 30 November 2019 04:14 PM   [ Ignore ]  
Avatar
Total Posts:  74
Joined  2014-03-14

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.

Profile
 
 
Posted: 30 November 2019 07:46 PM   [ Ignore ]   [ # 1 ]  
Moderator
Avatar
Total Posts:  7392
Joined  2011-03-03

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.

Check your Cineversity-Private-Messages.

All the best

 Signature 

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

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile
 
 
Posted: 01 December 2019 07:06 AM   [ Ignore ]   [ # 2 ]  
Avatar
Total Posts:  74
Joined  2014-03-14

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).

Profile
 
 
Posted: 01 December 2019 09:15 AM   [ Ignore ]   [ # 3 ]  
Moderator
Avatar
Total Posts:  7392
Joined  2011-03-03

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

 Signature 

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

Photography For C4D Artists: 200 Free Tutorials. Texture, Panorama, HDRI, Camera Projection, etc.
https://www.youtube.com/user/DrSassiLA/playlists

Profile