3
$\begingroup$

I am trying to calculate the volume of a 3D scanned object using the 3D Print add on.

The object was captured with a structure sensor/ipad and then imported to Blender (version 2.79). The scanned model is of a small box (~8x3x6cm), so simple at this stage. As the object didn't have a base when imported, I followed instructions from this web site to add a base using re-mesh and then smoothed.

I activated the 3D Print add on and changed to metric units with cm selected. I then asked the program to calculate the Volume of the object in the 3D Printing tab. The volume comes up as 0.0 cm³.

There are dimensions in the right hand side panel under "Transform" of 81.38x23.00x59.80 um. Again this isn't quite right as the dimensions should be about 80'000x30'000x60'000 um given my physically measured box.

Any help in getting the volume calculation function to work would be appreciated.

$\endgroup$
  • $\begingroup$ I fail to replicate the issue. 3d Print Toolbox addon seems to deal well with all kinds of wrong geometry. It even works with a sphere cut in half into 2 separate pieces of geometry. Could you share some screenshots of your mesh or the .blend file? $\endgroup$ – Martin Z Aug 21 '18 at 6:34
  • $\begingroup$ Thanks Martin. I would be happy to share some screen shots or files, but I am not sure how to do so on this format? I also don’t have any online storage to direct you to. $\endgroup$ – Ann Aug 22 '18 at 5:12
  • $\begingroup$ @ann, you can add image to your question by doing "edit" and using the relevant toolbar icon in the edit area. To attach blender files, visit blend-exchange.giantcowfilms.com first: that website will create a link to your file that you can then paste in the edited question (only blend files though) $\endgroup$ – Nicola Sap Aug 22 '18 at 5:37
0
$\begingroup$

μm is Micrometre, one thousandth of a millimetre (0.001 mm or about 0.000039 inch).

If you try to calculate the volume of 81.38x23.00x59.80 um it will be around 0,0001mm3 or 0,0000001cm3 that is to small and rounded.

enter image description here

If you want to measure object in imperial units you need to go to scene tab and select this unit system from presets:

enter image description here

$\endgroup$
  • $\begingroup$ Thanks for your advice Crantisz, always appreciated! I had selected cm from the Scene --> Unites menu :) I think the issue is scale as Nicola suggests below. $\endgroup$ – Ann Aug 22 '18 at 3:50
0
$\begingroup$

Select your object, scale it 1000x up (S, type 1000, enter), hit . to bring it back into the view, then Apply Scale (CtrlA > Scale).

Your object seems to be just a few micrometers large. If you have previously applied a scale measure using some reference stick in your 3D scan, probably something funny happened while importing the object to Blender: it would be a strange coincidence that your dimensions are almost exactly 1000 times off.

$\endgroup$
  • $\begingroup$ Thanks for your advice Nicola :) I do think the issue is scale. I have now scanned 3 different box's and each time they have come in at 1000x too small However volume may still be a bit of an issue as when I scale up and re-do the Volumes they come in less than what I would expect. For example, for the box above the physical object is 8x3x6cm = 144cm3, Blender gives dimensions of 8.14x2.30x5.98 = 111.96cm3, however blenders calculated Volume is 96.43cm3. This is nearly 50cm3 less than the manually calculated volume, quite significant when you are only taking a 150cm3 volume to start with $\endgroup$ – Ann Aug 22 '18 at 4:54
  • $\begingroup$ Another box, 23x11.3x16 = 4158.4cm3. Blender image 23.98x12.71x17.54 = 5345.94cm3. Blender Volume 3841.02 cm3. Large difference for a fairly square object. There are some variations in surface texture, and some internal structure before holes are filled in with re-mesh. Is this enough to make such a large difference? Ultimately I want to scan coral colonies (~15cm round) and get Blender to give Volumes. Online info indicates, scanned image should contain size info that Blender can read and extrapolate. I haven’t applied any scale measure, just imported the .obj file and asked for the Volume $\endgroup$ – Ann Aug 22 '18 at 4:58
  • $\begingroup$ My concern is that if I import a coral file, I won’t know what scale to use. It is looking pretty consistent though as I also checked a coral model that I loaded into blender and that also seemed to be 1000 off. Another concern is the Volume measure. Is there any way to make this more accurate that you know of? Thanks again for the advice :) $\endgroup$ – Ann Aug 22 '18 at 4:58
  • $\begingroup$ dear @ann, unfortunately I don't know much about the volume tool: the 3d printing add on is not one I use. I can only help you understand the mismatch between 8.14x2.30x5.98 = 112 Vs 96: the former is the size of the bounding box (that can be stretched out by any little bump in the model), the latter is the volume of the object, where morphology is taken into account. as for the mismatch between expected and obtained result, I'm not familiar enough with your process to identify the cause of concern, sorry $\endgroup$ – Nicola Sap Aug 22 '18 at 5:31
  • $\begingroup$ Hey Nicola, Thanks a lot for the response :) Your help has been very useful and appreciated! I will scan a few coral and see how it goes. $\endgroup$ – Ann Aug 26 '18 at 3:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.