SketchUp "SOLID" OBJECTS are damaged by modifications

Building a model for 3D printing requires the model to be a “solid”, which can be checked by looking if a volume is reported in the Entity Info. Solid models are also required for boolean and other operations.

During the construction process the model may have to be repaired after modifications, for example addition or subtraction of solids. On complex models this can be a very time consuming task. The “Fix Solid”, Fredo Tools “Edge Inspector”, “Edit Vertices” and other SU plugins, as well as external programs such as MeshLab are a very great help.

But errors will appear in zones remote from the modification, on previously corrected error-free zones.

Also exporting a SU solid in stl (or other formats) will produce manifold printable files but re-importing the file into SU will result in models with many defects (perhaps hundreds).

The Make Printable service will make a printable file out of almost anything. Curiously, importing these processed files into SU does not produce errors (or it has not happened to me yet). But I have not tested this extensively enough.

Can this be improved in SU so that less solids errors are produced?

Is this a general feature request or a question for help with a specific model?
Solid operations work for many users, but it is known that there can be edge cases. In any case more specific information and example models would be needed to make this post useful, either for improving SketchUp or for helping with your model(s).

Reasons for breaking volumes (or faces or planarity) are:

  • Too small edges (mm) close to the precision of SketchUp, too big geometry (kilometers), or geometry far from the origin
  • Some export formats may have a lower numerical precision, so coordinates become slightly rounded and vertices are slightly moved. This is often no problem when viewing the model in an external viewer, but when re-importing into a modeling application there are higher requirements (e.g. to detect multiple vertices that should be represented as one; or to allow snapping,). The geometry does not match numerically precisely to the original model. Some coordinates could diverge over the SketchUp tolerance and cause non-planar faces or holes.
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  • ‘Solid Tool’ operations on SketchUp Solids with mixed front and back faces on the outside of one or both of the involved solids when the operation is performed.

So I wouldn’t consider (nor should SketchUp) a shape with a mixture of front and back faces to be a SketchUp Solid.

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Alas, SketchUp DOES consider such a shape to be a Solid. I just created a basic cube - all faces white. Grouped it and Entity Info says “Solid Group”. Double clicked to edit, selected 1 face, context-clicked “Reverse Faces” - now only that face is blue. Exited edit, selected group - and Entity Info still says “Solid Group”.

Maybe my English isn’t as good as it should be. :upside_down_face:

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I would consider this to be a feature request and I agree that the best way to illustrate the problem is with an example. My file “Twisted example.skp” is too big to be attached but it can be downloaded with the following Dropbox link:

Dropbox - File Deleted

The group placed at the origin is a solid. Two identical copies were were added resulting in a new group which is not a solid.

Attempting to fix the new group with the Fix Solid plugin will result in about 76 highlighted defects. My point is that many defects are located away from the solids intersection zone, where no defects existed previously, implying that the Union operation affected the complete geometry of the model.

This is a fairly small model and could be manually fixed but for larger models manual fixing becomes unpractical, specially when many operations are necessary, each generating a large number of defects.

Nope. Your English is fine. You just pointed out something I wasn’t aware of, and found so … ahem … wrong (SketchUp, if true, not you), that I decided to do a quick test.

The fact is that a “solid” with one or more reversed faces cannot be 3D printed (I believe). But, if one single face is selected, the “Orient Faces” context menu command will orient all connected faces to match the selected one.

We can define a “solid” in SU as any group or component reporting a volume. Which is fine but several watertight separate objects can be joined into a single group or component and SU will report the total volume. Also, if each object is a solid group or component, they can be grouped by the “Outer Shell” or the “Union” commands into a single solid group reporting the total volume of the separate objects. Not very intuitive.

This is great as many separate objects can be used as a single solid in boolean operations. For instance, you can create a number of cylinders. group them into a single solid and subtract them from a flange to create orifices for the bolts, all in one operation.

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May be, as suggested by Chipp Walters at the Corner Bar, SketchUp is not the most appropriate software for dealing with large polys. But before engaging in learning a more complex program, such as Blender, I have tried, where possible, to find more efficient procedures within SU, which is a lot easier to use.

The attached file is a solid SU object drawn using a photogrammetry scan as a reference. But only a part of the original (decimated) scan (colored spring green) was preserved because of the difficulty of measuring the surface. The rest was drawn in SU (colored default white). The smooth transitions between the scan and the SU drawing were made by lofting (colored blue). An accurate, printable small size drawing results.

If this may be useful for anyone else I will be glad to provide the details.
Mixed build solid object.skp (1.2 MB)

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