Is SketchUp really the best starting point for solid stuff/STL?


I love SketchUp… just not sure it’s appropriate for what I’m trying to do. I think it’s not really designed for solid CAD and really is mesh. I don’t really understand the difference all I know is…

My workflow is:

  • generate object in specialist program, export with “Nurbs to STL” (rather than nurbs to dxf or step… or exporting profile/outline etc separately to reassemble)
  • reduce the poly count with meshlab down from 18,000 to 250
  • import STL into SketchUp

By the time it’s in SketchUp there’s a bunch of holes in the model. SolidInspector helped me figure that it’s not happening at the Meshlab stage.

I then try to plug holes manually but being a very curved object (surfboard) it’s a massive task even with FixSolid and SolidSolver. I then try to improve the process using ExtrudeTools but I can’t get my head round it.

My next move I think is to bring the STL into some other kind of program and then resave…then bring back into SketchUp.

However… I notice a lot of people use Rhino and SolidWorks. Surfboard shapers don’t have enough cash for these so I assume it’s pirated software. I wonder if I should be using a Solid CAD program like that (find something free like Autodesk123D?) rather than working around Mesh problems?

If so, where to start with that?


If you gave us some idea of what your end point is we could give you better advice.
What do you want to do with the models you create?


Thanks for getting back to me.

I want to be able to do a number of things.

  1. Slice the board to help me make the object in wood. I can do this in Sketchup but I need a solid model
  2. Export the model into a CNC program to generate g-code
  3. Just visualise the thing, maybe make a small 3D printed model


You should be able to do this but you have to keep in mind that sketchup works with triangles. If you don’t have the surface smooth enough you will get the faces as they really are.
But that depends also on you printing resolution and also the scale of your object.


I’d have a look at Tig’s Extrude tools and Fredo6’s Curviloft.
Both will allow you to build complex curved faces that will easily combine to form solids.
If you happen to have a plan and profile of a board lying around, attach them and I’ll see if there is an easy way to demo one.


That sounds like a very drastic reduction, is there a reason for this?

You should import as meter to prevent the small faces problem.


I only reduced to 250 for testing while I try to figure this out. My computer might take a few hours to do the full model. I don’t need much detail actually. Probably around 5k faces is enough.

Import as meters seemed to have an effect but not enough. I’m wondering if BoardCAD (the thing exporting the STL) is making broken meshes and that’s just what I have to live with.

I’ve seen TIGS Extrude Tools but they baffle me a bit as I’m not that advanced yet… I try to use Face to Face but I’ll need more time to work it out for this purpose. I haven’t found a demo video for covering up holes yet - that would help.

the original ~20k face:
nurbs56.stl (2.3 MB)

250 face if you find it useful:
250 face

I’ll check out Fredo6’s Curviloft now - trying to find a instruction video for that.

Thanks for the attention, seems like a common skill to master? Just a bit advanced as I happen to be working on a very curved model.


The original 20k mesh is perfect(except for the two front/back holes which are easy fixable).
For a full scale on cnc I would say you have to smooth it further inside sketchup or smooth it in the Gcode creator.
For a small scale print it is also perfect.
Why would you want it reduced to 250 edges ?


Thanks for this. My computer is so slow that the original model takes >30mins to intersect the same model shrunk in order to hollow out the object… so I hadn’t actually tried to inspect the bigger model at metre scale. The lower poly count had made the holes a lot worse. With metre scale and high poly this is now manageable :smile:

So now I’m filling the holes. I can do it slowly but I’m wondering what the best way to do it is.

What would help would be:

  1. To be able to select lines only by the point select tool …or even by lasso
  2. Pinch together these selected lines

Because what I have to do at the moment is select one half of the hole, move it to the centre of the hole, and then do the other half. The more polygons there are then the more I have to click on with ctrl.

Just to help anyone who finds this thread and has a similar problem:
“SketchUp cannot create edges < 1/1000” long as the vertex-points are deemed to be coincident.
Then any faces that those tiny [omitted] edges might support are not made.
If you Scale up by x10 or x100 the tiny edges/faces might form.
After your processing you can Scale back down, because tiny edges/faces can exist - BUT they cannot be created !"
(can’t post link unless create a new post - it’s thread 4623)

It would be great if I could just select all of the perimeter of the hole and click “fix hole by generating surface” or something.

Related thread:

I think TIG Extrude by Edges can help… just need to learn how to use it… in this case I want the path to meet up with the other side so I’d have to create a path for it… but what I really want is for the tool to create the path for me by looking at the other side of the hole - creating a path by hand for a curved surface could be a lot of work… not any faster?
It does create the ability to create a complex surface though - that’s useful. What it doesn’t really do is allow you to just quickly join the hole.

edit: A reference image to help anyone looking:


some suspicious lines in yellow highlight…


If you simply draw a line from a side to the other the hole will fill because the perimeter is coplanar .
The problem with a solid object would be the geometry from the right of the image which touches the newly created face.
Also, it seems that the back is a bit out of shape, is that how is supposed to look?

This picture show how you can fix the problem.


Depending on what you want to do, you could half the geometry… literally: just cut the board down the middle and erase one half, turn the other into a component and flip it.
(Of course you would need to explode it all and group it again for any 3D printing output.)


Thanks for your help.
To be honest I didn’t want to reply because you’ve been so helpful.
I’ve been at this for nearly a week trying to figure out what you mean as to how to close it - drawing a line halfway and then joining to the side of the hole.

I can’t get it to close. I’m sorry. I’ve been trying for hours and hours.
It looks closed but it’s not. stiching2.skp (1.2 MB)
I didn’t reply before because I feel so stupid :blush:


actually I think it may have worked and it’s the 2nd stage that’s not doing what I expected.

I group the object, duplicate it, shrink it, then intersect (this takes 20mins) and then delete… but when I delete the object doesn’t appear to be hollowed out


I am not sure you can make it hollow by shrinking a copy because when you scale the object you scale it in all direction and at some places faces will touch. You should use Joint push&pull but you will have to make further adjustments to it.
If it was a cube or a sphere it would have worked.

No intersection should be made if the model is well made. Maybe just cut a small hole trough both for the excess material to be collected if necessary.
Also, you did something that detached the underside from the body.