I am a relatively new user to rhino and have been using an Artec 3D scanner to scan images and import into rhino with the intent to accurately measure volume. At the moment we have been practising on cylinders with known volume but I wanted to know the best way to accurately measure volume. I have been using the following sequence:
Import OBJ file
ReduceMesh (95%)
Select mesh and ReduceMesh (95%) again
MeshRepair
Fill ALL holes
Calculate Volume (mm3)
However I have found I get different values depending on the percentage I reduce the mesh by, but if I don’t reduce the mesh Rhino can’t deal with the images. Can anyone shed some light on the optimal percentage to reduce by and why?
We found some of the commands we tried Rhino would say too many surfaces and shut down. Initially I was trying to draw a closed line and also found this difficult.
Hi Cristy - it would be good to know exactly what commands - for example, I’ll just guess MeshToNurb, and if that is the one, why are you doing this? The Volume command should work on the mesh directly if the mesh is closed and valid (Check command)
Thanks, yes MeshToNurb was one that didn’t work. I guess what I am asking is what percentage of polygons would represent the true shape? Perhaps it is my limited understanding of Rhino, I have tried researching this and haven’t found a good answer. The volume function actually does work but the volume produced is larger than that calculated. Given it is important we get in accurate to mm and I have found I could reduce the mesh quite substantially and still get a reading I wanted to know what the optimal reduction would be or if anyone else has tried this. So far I have found 95% and 95% seems to work but on some images it reveals naked edges etc that I can’t repair to calculate an accurate volume but at only 95% reduction it is possible to get a volume. I would like to be able to use the same number for all the images.
Thanks! Cristy
Hi Cristy - can you send us an example obj file that is showing the problem? Smaller is better as long as the problem shows up. (tech@mcneel.com, to my (Pascal) attention) If the file is very large,please zip and upload to www.rhino3d.com/upload.
Hi i want to measure volume just like you for a research project , but a popup appears as “some of the selected objects are not closed, this calculation is only meaningful if the selected objects fully enclose a volume” what do i click or do to rectify this in order to obtain a accurate volume ?
Thanks !
@shenalisilva1994 Have you done any modeling with Rhino or is this you first use of Rhino?
A volume in Rhino is a closed surface or polysurface (multiple surfaces) and the edge of each surface is joined to one, and only one, other edge. If one or more edges are not joined to other edges then the surface is not closed.
Hi !
Thanks for the reply , this is my first time using it , there seems to be naked edges in my model , how do i rectify this ? Unless i obtain a closed volume i cannot obtain an accurate reading …
thanks in advance
It is impossible to answer your question based on the image alone. You will need to modify the object to close it and remove the naked edges. Is the object a mesh? You can upload a .3dm file with the geometry by dragging the file to where you type a post, or by clicking on the vertical arrow icon above where you type a post?
