Why does my Sketchup model get distorted when I export it and then import into another editor?

I usually use Tinkercad to add details that I don’t know how to draw in Sketchup Web, but when I export the model as an STL file and import the file into Tinkercad, parts of the model have collapsed into triangular distortions. I looked inside the model on Sketchup and did not find any extra lines that could account for the distortion. Is there any possible explanation for why this happens? If so, is there anything that I can do to fix the problem?

The model looks like this on Sketchup:
cmc_sketchup

But when I import it in Tinkercad, this happens:
cmc_tinkercad

It also happened with a model that I downloaded from the 3D Warehouse and tried to modify in Tinkercad.

Hi there: would you mind attaching the SketchUp file that was the basis for the STL export? I’d like to take a closer look to see if there is something up with your model or SketchUp’s STL export.

(You can download the SKP file for this model by going to File > Download.)

CMC Attacker it1.stl (165.4 KB)

I checked the model thoroughly for extra lines. I inspected the model, downloaded it as ans STL and opened it in Tinkercad multiple times, but the tailfins and decklid were still distorted. I was able to patch those particular problems up in Tinkercad by adding geometry over the distorted sections, but I have already had experience with one that I was barely able to fix and I would rather not have this problem in the future, especially since it’s entirely possible that this type of distortion would occur in a way that I would not be able to compensate for.

There are several things wrong with your model, firstly you have included the scale figure.
There are quite a few holes in the structure and internal faces, both of which stop it being a solid.
But the distortion issue is being caused by the back section having reversed faces.
Faces in sketchup have a front and a back face, front White, back Blue/grey. The orientation of the faces tells other software what is inside and what is outside, so the back end of your car is twisted insideout.
When looking at your model without being painted (view Monochrome) you should only see white, if you see blue you need to reverse it.

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So, that’s what’s happening, but how do I find and fix the holes and reverse the faces?

If your model is symmetrical I would cut it in half (put a flat plane through the middle and use intersect faces to create a line, then delete one side and remove the faces of the plane), look for and repair any holes and delete extra faces, right click on any blue faces and select Reverse Faces. Once you have half fixed, make a copy and flip it and put them back together.

Your model is also Tiny so I would suggest you scale up by 100 or 1000 then scale back when finish, or export at the relevant scale.

I have two questions about your suggestion:

  1. How do I put a flat plane through the model?
  2. What are intersect faces and how do I use them to create a line?

Those questions suggest to me that you haven’t spent much time learning the basics. We are happy to help here but we aren’t here as teachers, you need to spend some time learning from the basic videos and such.
However, what I would do to start with this,
open the group and delete the scale figure.
Move it to the origin and place the very point at the front right on the origin point.
You can explode the group at this point, edit it then regroup it, which will move the groups origin point to a more appropriate location.
Draw in a rectangle, since you have centered it on the origin the rectangle will be drawn at the midpoint of the geometry.
Select it all and Right click, Intersect Faces with selection.
Remove the plane and one half.
Now you can see the extra faces inside, the reversed faces at the back and the holes on the areas around the door frames.

Split

That worked for the tailfins, but, when I upload the new resulting STL file into Tinkercad, the decklid looks like this:
CMC_tinkercad_decklid

and the A-pillars look like this:
CMC_tinkercad_a-pillar

I’m certain that nothing that I can find in the model accounts for the decklid. Here is the new Sketchup file:
CMC Attacker (1).skp (403.8 KB)

I’m still seeing reversed faces where you have problems.
Also all that stitching around the doors can be removed by deleting it all and connecting the correct points together to form flat faces.
Some printer software lets you get away with holes and non solids, but it’s better to make things correctly.
Reversed%20faces

This is what it should look like when you have repaired it.
SolidCar

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In a previous reply, you mentioned viewing the model in monochrome. I searched through the menus in the editor (free Sketchup Web) without finding such a setting. Does the free version of Sketchup Web not have monochrome view or is there something that I have overlooked? Perhaps the main reason that I have failed to spot some of the reversed faces is that I can’t see them because the model is painted.

Yes, Unfortunately Monochrome is unavailable in the free web version, the upgraded web version does have Monochrome. But that doesn’t help you.

The only option I can find in free web is to paint the faces with ‘nothing’ which will revert all the front faces to the default material ‘white’ and show any reversed faces with whatever they have been painted with. The downside to this is that you would need to go through and repaint all your faces again. (We generally recommend not painting anything until you have finished modelling.)

One way around this is to make a copy and paint it with nothing, then correct the faces in the original.

FreeMono