Rhino Sketchup export triangulating surfaces

Hi - I’ve discovered that when I use the Rhino Sketchup exporter (direct export to skp file), I get great results (layers, materials, vectors all translate perfectly), EXCEPT the resulting geometry is always triangulated. This is evident when turning on hidden geometry in Sketchup. This result is absolutely deadly for any further editing work in Sketchup, or for exports from SKP to Vray or other renderers. On the other hand, using DWG export from Rhino to Sketchup yields great untriangulated surface geometry in Sketchup, but vectors and materials/colors do not translate. Is there a fix, or can the Rhino Sketchup exporter be fixed?

Working in a studio where Rhino and Sketchup are both used, there is always a need to translate geometry back and forth, so the Sketchup exporter is essential. It is so close to perfect yet the triangulation is a dealbreaker.

Thoughts, suggestions?

Thanks,

Matthew Winkelstein

Hi Matthew - I guess this is done to force planarity since skp insists that polygons be planar. If you set ‘Combine planar regions’ does that over-simplify in skp for your needs?

If I send non-planar quads via dwg, it does come in to skp but not exactly correctly…

-Pascal

Hi Pascal - I cannot find any “combine planar regions” control in the Rhino to Sketchup export dialog, and it does not appear as an option when opening the resulting Sketchup file. Even when surfaces in Rhino are 100% planar, the Sketchup exporter splits them. Oddly, this is not the case when exporting Rhino surfaces as DWG and importing the DWG into Sketchup. Since this can be done with DWG, I was assuming the direct Rhino Sketchup exporter could support the same functionality. Note that with Rhino surfaces triangulated in the export process, the resulting geometry surfaces in Sketchup cannot be extruded using the Sketchup push/pull extrude tool, since, even if the diagonals are hidden, Sketchup editing tools read the triangulation. It essentially renders the resulting geometry useless in Sketchup, unless you go in and manually remove the triangulation divide lines in each split surface (after turning on hidden geometry). As mentioned, other than this issue the Sketchup exporter is far better than other methods for getting geometry from Rhino to Sketchup, as it retains all texture maps, color, layer structures and vector lines (curves) - which is not the case for the DWG route.

Matthew

Look for “Export planar regions as polygons” in the window which should open when Export or SaveAs and .skp is the file type.
Testexport

Yes, I always check that but it has no effect on the result. When you turn on hidden geometry in Sketchup for surfaces exported from Rhino (even with that checked) you see each rectangular surface is split/triangulated. Sketchup views this as separate surfaces. You won’t see the diagonal division line if hidden geometry is turned off in Sketchup, but the editing tools (e.g. extrude push/pull) do not work because the actual surfaces are subdivided.

Matthew

Btw, testing Rhino dwg export to Sketchup instead of direct-to-sketchup, with merge coplanar surfaces checked, and the result in Sketchup is different. When turning on hidden geometry with the dwg import and there is no surface triangulation (and the geometry is fully editable).

Hi Matthew - where is this setting, in Rhino’s export (?) or in skp? The developer tells me it is easy to allow quads in our code, and if skp can handle non-planar quads better than, I guess, it used to, then we can just do that - we’ll have a try in V7/WIP and see how that works.

-Pascal

Hi Pascal - merge coplanar faces lives in Sketchup in the dwg import dialogue. I find that importing Rhino geometry in dwg format eliminates the triangulation issue (but as mentioned the other negatives with dwg import remain). It would be ideal if the Rhino SKP export could have this option. Would love to try it in the Rhino 7 WIP. Let me know! Thanks.

Hi Matthew - thanks - I am not a sketchup user beyond testing so bear with me but if I export a mesh box (simplest case!) from Rhino, that has four quads to box face, and I bring it in sketchUp via the current skp exporter, I am allowed to move the overall faces on the box in skp, but there is no sign of the individual quads on each box face. Hidden geometry does not change anything that I can see… can you tell me what I’m looking for in this case that is wrong in SketchUp?

-Pascal

Pascal - here are a few screenshots (sorry for the bad writing). This is a simple box exported via Rhino SKP exporter and imported (or opened) in Sketchup. It looks ok at first glance but when you try to work with the geometry you find that the extruder (push/pull command) fails since each rectangle is actually two triangles. If you go to View in Sketchup and check show hidden geometry, you see what this second screen grab shows - the dashed lines are the actual face divisions. Unless you delete the hidden division lines, the geometry is almost impossible to work with. Btw, I am not working in Rhino in meshes, only nurbs surfaces.




Hi Matthew - thanks - that is what I expected to see, but I don’t - but -are you exporting meshes directly, or breps that are converted to meshes on export?

My mesh box in Rhino:
image

Export:

Push-Pull in skp:

Does that look correct?

-Pascal

I should mention, too, that while Sketchup hates nonplanar surfaces (as you noted), as long as the originating Rhino surfaces are in fact planar they should not be triangulated, as the current SKP exporter unfortunately does as a default action.

Also, to clarify, in the above screenshots, the one that has the Sketchup error message “cannot Push/Pull curved or smoothed surfaces” is actually showing that the push/pull (extrude) command only works on single planar surfaces, so two joined triangular surfaces (even with division hiddden) will not extrude. So the incoming geometry from Rhino looks great initially but editing is impossible unless the hidden divisions are cleaned out. With hundreds of surfaces on a complex building model all tessellated, cleaning that up becomes challenging.

Hi Matthew - in my screen shots though… does that show what you’d expect to see but do not, or am I doing something different?

-Pascal

Pascal, I am working in standard Rhino nurbs surface geometry, not meshes. Try your box experiment with a Rhino 3D solid, not mesh.

I simply do “export selected” of my selected Rhino architectural model surface geometry and select Sketchup as the export format. For modeling detailed buildings I had not thought to use or convert to meshes.

OK, got it. What happens if you mesh the objects yourself before exporting? (Mesh command)

-Pascal

That doesn’t seem to help: here’s what I get from exporting to SKP a mesh box (shown with hidden geometry on)

Hi - I wonder if this might have something to do with the version of SketchUp that’s being used…

I only have 2015 here (which doesn’t import DWG) and NURBS geometry exported as SKP does show those hidden lines but NURBS geometry exported as KMZ doesn’t. A MeshBox from Rhino exported as SKP also doesn’t show those lines.

But none of these can be edited with the Pull/Push tool…
… in the 2015 version.


-wim

@wim , @mwinkelstein - I guess when exporting breps directly, we use the render meshes - this is to ensure that block hierarchy is maintained - if you Mesh blocks, that is not maintained. That is why there is no meshing step when exporting to skp. So… it may be tedious but it may be worth at least a test: Make custom render meshes for your objects use settings that tend to make the simplest most ‘quady’ render meshes. On a box, just to test, for example, use something like this:

image

-Pascal

Hmmm - maybe I’m doing something wrong, but i set one of two boxes to your render mesh settings (1 quad, etc.) and kept one at the default render mesh settings (16 quads, etc.), exported both to SKP, and got the same triangulated result in SKP for each: