Meters to Millimeters


#1

Is it possible to change the scanner’s unit of measurement from meters to millimeters? ( To increase small scale accuracy and make the .obj file more friendly to our 3D mill)

We are using this scanner in a medical application to scan a patient’s foot and build a device to accommodates amputations, diabetic ulcers and other deformities. Our software is creating great images of the foot, but the measurements can sometimes be off by as much as .5 inches… which is a big deal in our application.

Right now our milling software is looking for measurements in mm, so we are hypothisising the 1/2 inch discrepancy (or some of it) might come from a rounding error in the software when it reduces the .obj from meters to millimeters.

We would like to get this scanner as accurate as possible for this application. Are there any other tricks we should try to increase accuracy on objects the size of a human foot?


Making scan actual size/measurements in Meshmixer
#2

@codyballantyne are you developing an app or using Scanner from the AppStore?

A unit change wouldn’t affect accuracy. If the downstream requirements are for mm, just do the scaling when saving the data.

Be sure and scan as closely as possible to the object / subject for the best accuracy. Also tighten up the placement cube as much as you can.

-jim


#3

Hi Jim,

Due to the smaller scale and the short target distance of our application, we are developing our own app. Our programmers disabled the gravity of the bounding box (it’s floating) and brought the focal point as close as they could to help with tracking, and the limited room found in a Doctor’s exam room. Now the only thing that stands in our way of launching the app is this 1/2 inch measurement discrepancy we are seeing in our scans.

(we scanned a box, measured it’s dimensions and compared those to the 3D model. The 3D image is consistently reading 1/4 to 1/2 inch too large)


#4

What value is used for initialVolumeResolutionInMeters? Can you send a screen recording?

-jim


#5

We set it to: float initialVolumeResolutionInMeters = 0.005;
After that the measurements were very close to the real thing.
However with another question that we asked about we setup: STCameraPoseInitializerStrategyGravityAlignedAtOrigin
And haven’t tested it yet. I’ll go back and see.

I am curious if you know of a place online that would explain more in detail about what “voxel” is in 3d graphics.
I’ve done some searching and found some information. If you have any preferred websites it would be of great help.