Working at mm scale

Hello,

I’m having some weird issues working at a small (mm) scale. Sometimes I can work just fine, but other times I have extreme difficulty with navigation, rotation, and just working in general. It’s just super hard to control the view.

I’ve attached two files, cylinder_tester.blend (which is difficult to work on) and testcolormount.blend which is just fine.

I don’t even know how to ask this question properly, just–what gives? :smiley:

testcolormount.blend (528 KB) cylinder_tester.blend (472 KB)

Are you going to be using your models for 3d printing? Will you only be working in millimeter?

If you’re only using the scale as a reference then you can change the scale in the scene tab to 0.001 or 0.01 .

This is the biggest issue with your scenes. You’re not actually using any of the unit presets. You’re working in Blender units and trying to work lower from there. The difficulty with that process (unless you assume 1 Blender Unit = 1mm) is that as you get to smaller values, you start encountering floating point errors. Blender only has single-precision floating point accuracy.

In other words, use CAD software for work requiring precision.

I feel your pain- it sucks for industrial design for humans- because these kind of products ( up to the size of a car) are designed in millimeters. Working in cm is a little better. You might have to go unitless. Install the Measureit addon which comes along by default in your addons. At least that will give you a sense of scale. You could work at meter scale and scale down. Parent your work to an empty and then scale and up and down for exporting out of Blender

with normal scale = 1
you get precision 9999.999
so this is 1 mm if you use Meter units

but change your scale scene to smaller value
and you get more digits on the right after the dot

blender in any case is limited to 7 digits independent of the scale

happy bl

That is a poor advice in my opnion. I believe trying to do it as it’s supposed to be done first would be a good idea. If greater precision is needed, the units should be set to milimeters first:


One would need to set correct clipping distatances for viewports and cameras after setting this.

I work with milimeters quite a lot and experience no problems with scene being set to meters. You can work with object as small as 0.001 mm.

Rastoboy, could you describe in more detail what exact difficulties you are experiencing and what exactly you want to achieve?

Thanks for all the great responses. To clarify some of y’all’s questions:

Yes, I’m doing this for 3d printing. Blender works just fine for this (and I know how to use it reasonably well). I just get this weirdness when I shrink my model down enough. I am using MeasureIt, in fact, so that’s where I’m getting my millimeters.

Weird thing is…I scaled my problem file up to cm scale so I could do some work on it, and somewhere along the way I did something that affected it so that when I shrunk it down .1 scale to mm scale again, I can move around and use it just fine.

So it appears I need to do some more testing and try to isolate what causes this problem–and when it does happen again, I’m going to try tweaking the scene scale as several of you suggested.

I’ll update this when I run across useful information or a way to reproduce the issue at will.

Thanks again!

lee

The thing is I cannot replicate any issues at all with the files you shared. Are you using 2.78? After pressing numpad . key with the cylinder scene, the view jumps to the selected object and navigation works as expected for me and I am unable to find any more problems.

sigh, after my last post I tried to replicate from scratch, and failed. It’s happened to me several times now…and I’m just going to have to keep my eyes open, I think. It does seem to be when I’ve started Blender up and started something new, though. But not every time…

It’s probably helpful to know you couldn’t replicate. I’m on 2.78c

But it would be so lovely if my favorite, almost-all-purpose, 3D modelling, animation and video-editing program could also do CAD. It would make an awful lot of sense if it could. :smiling_face_with_three_hearts:

Hi the unit setup is only a convention to work for printer you can work with default setting without changes, in fact the most CAD assume that is a mm units, you can keep continuing work with default and don’t change anythings assume 1 is mm and in the conversion for your printer you can changes the scale in second time if you have any scale issues to desired scale in exporting time. I works with CADs and I always work with default scale if I to do an exchanges between CADs. some times I adapts to other system but that is very rare cases.ù

EDIT
attached Blender file scaled up to 1000
testcolormount_Scaled_up.blend (579.9 KB) cylinder_tester_scaled_up.blend (517.1 KB)

Thanks for your insight on this. As a product designer I do my conceptual work in Blender and model in Solidworks for production. I use the Stepper importer from @ambi to import mechanical parts as .step file. https://gumroad.com/l/stepper In both Solidworks & Blender I work in mm units, as I like not typing .00 before every Blender transformation. In Blender I have set the unit to mm, and the scale to 1. The step files come in mm units, and then I can work in mm as always. When I export as .obj I only have to scale everything 1000x in order to have the correct scaling back in Solidworks again. This is fine by me, and works good.
Screenshot_489

The only downside I currently experience is when I change the values in Viewport->Item->Location, the dimensions increas 10mm with every click. And I would prefer that to be 1mm.
Screenshot_490
If I am right, in your workflow that is not the case and you can just work in the Blender scale.

So if I set Blender back to meters, and have the importer change 1mm->1m, then I can use the blender scale as default in meters. When I export in obj again I dont have to change the scale I think. I will try this out. :slight_smile:

Edit: I found that in this specific case, if I hold shift while changing the value, it changes in one unit more precise. It also works with the Bevel modifier (through HardOps), holding shift changes the unit to mm, which is sufficient for me in terms of precision.

1 Like