What dimension do people use? 1m vs 1mm for micro models


When working with models with detail that’s below 0.01mm it often has issues with arks etc. By this I mean they don’t form because of being too small (cant remember the exact message).

Therefore I have started using 1m as 1mm so I can use the RoundConer tools and the likes of when it’s only 0.1m (0.1mm equivalent).

The problem I’m finding is that when I use textures in Vray, they don’t display properly, as anything above 254m in width shows as heavily pixelated. This is something I have raised with them directly, so no need to talk about this.

With the problem above, I guess I could create in meters, then downscale my products to mm. This would then solve any issues with Vray, and I guess it will make life easier in general, as anything I import will most probably be real world dimensions.

Just wondering what other people do to get around similar problems?

I’m starting to think I will create individual bits in M, then export to a file in MM. I mainly work with small rooms with doors and associated door hardware. So I could have separate files for the hardware in meters (door handles, closers, locks, door leafs) and a separate file for the whole model (doors, walls, floors, lights, windows etc) in mm.

Am I going about things in the completely wrong way?



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Are you familiar with the “Dave” method of using scaled components to deal with SketchUp’s small-geometry behavior? I (and many other people) use this all the time, it is very useful for screw threads and mechanical fittings with small details.

Edited to add that I work in inches, and I use a scale-factor of 100 with the above method. The 100X scale still encounters some small-face problems, but not many.

A larger factor such as 1000 would probably avoid most of the remaining small-edge issues, but it would exacerbate another of SketchUp’s problems - clipping when the camera gets “close” to geometry. In my model I have 1:1 scale objects and one or two 100:1 scale objects that are under development. I sometimes need to look at the 1:1 portion of the model for context, and the 100X objects cause clipping when I examine the 1:1 part of the model closely. I think the clipping would be much worse if I used 1000X copies.

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I find it extremely odd that in the digital age, it creates issues with these kinds of sizing’s issues.

As you have said, the faces often cause issue, and also as you have said, clipping becomes an issue. Also I notice odd zooming problems e.g. hyper sensitive.

I guess I will just need to do as you say, work at 100x or 1000x then scale down!

My only wild guess is to do with rounding? Perhaps when something is 0.134235345mm it can only reach a certain number of accuracy without taking up loads of space on the computer memory, so there must be some kind of rounding that goes one which then I guess means the system has to estimate the start / end points and joining accordingly!?

To be honest my brain isn’t big enough to understand why even if someone told me, so I guess I will just have to work with this @Dave method!

Thanks for the info, very helpful.

I too scale up things 1000 times. I set the model unit to be m but I mentally think of it as mm. Gets decals and 3d printed model locomotive bodies done, although I wish we could do this out of the box without such a workaround.


Some background is that floating point number calculations aren’t precise. You can’t possibly express things like 1/3 in a finite number of decimal places, not to mention pi. At some point all values will be slightly rounded in a 3D modeler.

SketchUp was originally designed with architecture in mind and not these small items. When the tolerances were first picked no one knew people would one day want to have smooth looking curved faces with a radii of half a mm or so.

There has been some discussion of tweaking these values or make them dependent on model extents.


I generally use 1000x when I use the Dave Method although for things destined for 3D printing, I just do as @ene_su suggests modeling in meters but thinking in millimeters and don’t bother with scaling down.


I work with 3D printers, so I’m typically dealing in 0.2 to 1.0mm kinds of measurements, but SketchUp is ultimately better suited to larger scale modeling (given its architectural roots) where precision to that extent is less important since it’s only a very small step in a much bigger process. Ask anyone who’s done any sort of woodworking or basic construction how much tenths of a millimeter matter with 2x4’s that aren’t really 2" by 4".

In short, I just move the decimal point over one and scale everything down later, ex. 1mm becomes 10mm, and when I bring the model into my slicer, I just scale it down to 10%. It sounds silly, but I like to think of it as a kind of encryption, like leaving out an ingredient on a family recipe. Had I Dave’s clout, experience, and reputation, I’d call it the Kadam Method, as in, “Then take back one Kadam to honor the Hebrew God, whose ark this is…” and you get the idea.

If I need to show off a model in scale to someone or make a technical drawing with all the right call-outs and measurements, I’ll either put an appropriately scaled version elsewhere in the instance using tags to toggle visibility, or I’ll make a whole new instance (especially if it’s part of a larger project that’s going to need to have other components imported into it) and offer that up as my first draft for submission.

What you’re describing with importing and exporting in M and mm is essentially the same thing that I do, just with our “one Kadam” in different places. If anyone asks why you don’t just use X CAD program instead of adding these workarounds, and you respect them too much to hurt them, just tell them all the other features SketchUp has, like its style builder or its awesome community.

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thanks for feedback all

FYI here is the link to my issue with Sketchup / Vray in regards to x1000


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