Digitize points onto a surface



Hi All,

Is there a command that can be used to digitize points to a surface?

What I tried unsuccessfully doing is this:
Create a 3 or 4 point surface from digitizer picks on an existing surface of an object.
Then set the construction plane to that surface.
Then digitize picks along the edge of the thing I’m digitizing, which is the perimeter of the surface.
Only thing is, the points are in 3d space, and do not land on that surface plane.
Can someone tell me a simple and effective way to accomplish what I’m trying to do?

Another thing I want to do is make a circle on a surface by 3 pics of the digitizer.
All the digitized points fall in 3d space. So the circles are not planar.
Is there a command to make digitizer pics fall on a construction plane?
Reason I ask is b/c I’ll be doing this for various shapes, and want them all to fall on the construction plane.

I don’t want to use snap-to-surface, b/c it adds an enormous amount of work while digitizing zillions of points.

Thanx! … Chris



if you’ve set the CPlane inside Rhino, enable Project in the OSNAP palette, then start DigClick or Points command from the 3-D Digitizing toolbar, all points picked with the digitizer should now fall on the current CPlane of the active viewport.

For picking points on a Rhino surface with the digitizer, this should work too. Use the _InterpcrvOnSrf command which is in the 3-D Digitizing toolbar, the button tooltip reads “Interpolate on surface”. Note that before picking points, you have to select the surface in Rhino, works best if you just pre-select it and position it in the Rhino viewport so you can look from above on the surface. Make sure the distance between the points do not vary to much, it influences the curve a lot.

The third request i never tried before. For picking a circle on a surface, start the _Circle command with option _3Point. When it asks for the first point, enter PersistentOnSrf in the Rhino command line and select your surface, then try picking the points with the Digitizer.

btw. all 3 tasks work best if you maximize the viewport with that desired CPlane or selected surface…and probably move your mouse pointer outside of the viewport so you can see where the digitizer is.



Thanx clement.
Your advices are appreciated!
Turns-out that my part is too big for the 66" MS digitizer, so it has to ‘leap frog’.
The problem is, the 3d data is 1/8" shorter than the part at its OAL.
I figured that’d happen, which is why I wish I could afford a 12’ CMM.
I’m going to give it one more try, then I will throw in the towel.
This is really bad for me b/c it’s the first job I was unable to do in my entire career of over 30 years!
Sad thing is, it all comes down to MONEY.
I just don’t have the MONEY to buy the tools I need to do this job.
That’s how it is when you go from the ‘little time’ to the ‘big time’ where the criminals live!
Cheers … Chris


Hi Chris,

one way to digitize objects larger than the overal arm length is to work with multiple coordinate systems. Your csys should be attached to the real world model. Create one cycle, starting with 3 points for the csys, then when you cannot reach areas too far away for the digitizer, move the real world model so you can reach missing areas, and the 3 points of the csys attached to the real model. On a new layer, digitize all missing points. Once done, align both sets of points from the two layers using Orient3Pt.

This works best if you have some kind of movable plate with the 3 csys points milled into in a conic drill, which exactly fits the digitizers cone tip. The farer the point on X and Y is away from the origin, the more accuracy you’ll have when re-calibrating the MicroScribe to the Rhino document. I use a distance of 30cm.



Thanx clement.

I already did that. I made plates w/X,Y&O (origin) like the Rhino “Leap Frog” tutorial says. It’s a bit different from the instructions you say, but it mitigates me having to align the scans after the fact. They automatically align during processing.

The problem is tolerance build-up w/this G2LX.

Turns out, upon 2nd measuring, it was only 1/16" off over 50 OAL.
That’s not too bad, eh?

I’m going to give it a try to see how it works in real life.

Thanx for your input.



What software do you use to process your point clouds and meshes into surfaces that can be used in 3d parametric cad?

Thanx … Chris


@cadman777, the software included with our scanner creates the meshes from the pointclouds which i clean up using various freeware before i import it into Rhino. Then it depends on the model if i only use Rhino to remodel or sometimes RhinoReverse. There is nothing parametric as almost everything we scan is fully organic.



Thanx for the info clement.
What “freeware” do you use (I might have asked you this question before, but don’t recall)?
Are any of your models high tolerance parts?


That too much to list, i try out everything and see if it fits for my work, eg. Blender for Retopo and rendering, CloudCompare if our scanner software cannot handle the pointclouds, MeshMixer to quickly fill holes and remesh etc.

If 0.001 mm is high tolerance then yes :slight_smile:



I just began using MeshMixer and MeshLab, but CC & (esp.) Blender are a bit difficult for me to learn.
Just wondering what you use to get the job done. Was hoping there was a nice simple solution out there.

My biggest hangup is the time spent fixing the mesh and getting it ready for 3D parametric CAD. Still haven’t found a work-flow for that yet. Still stuck between mesh and 3D CAD. I looked at Mesh2Surface, but it’s too pricey for the functions it provides. I consider it worth around $300 tops. Everything is so expensive these days.

Yup, .001mm is EXTREME!.
I would be satisfied w/0.001".
What scanner is giving you that level of tolerance?


That is not the scanner tolerance but the one i model with in Rhino. The scanner never goes below 0.05mm. If you like post or send a typical model via PM and i may recommend something to fix the mesh.



Oh, OK.
I’m just curious, b/c I’ve been doing a LOT of research on this, and also trial-and-error (spent some $).
Which scanner is giving you .05mm accuracy?


A MicroScan mounted on a G2LX if all conditions are really optimal. eg. material of the object is pure matte white and mounted to the table to prevent wiggle, device is calibrated, lenses cleaned, no disturbing light etc… If this is not the case it reaches only 0.1 - 0.15 mm. It also depends on the size of the object. Larger objects tend to produce more deviation. However i do not give much about scanning tolerances as i have to smooth clouds and meshes in order to get a useable base for reverse engineering.



Considering DesignX is $10K +, and it doesn’t really handle organic stuff, Mesh2Surface is not a bad deal. :slight_smile:


I have a G2LX too, but it’s beat to shreds (came off an MRI machine) and only gives about .03" accuracy.
I like it best b/c it’s very easy and simple to use.
Only thing is, the arm gets in the way of measuring stuff, and also the leap frogging kills accuracy.
Also, costs too much to get calibrated, and don’t want to risk being told it’s unfixable or it’s got problems that’ll cost an arm and a leg.
Got it for around $350.

So basically, you use a CMM+laser.
That’s what I was wondering.
That was my other option, but was way too expensive.
Considering the costs of these systems, seems like you’re damned if you do and damned if you don’t!
I find that almost all of what I measure can be done by hand measuring or a combination of tracing+scanning on a flatbed scanner+tracing over in Autocad, and then hand measuring for accuracy after building in Inventor.

Yeah, DX is $20k. Having used it, at most I would give $3k for it.
Those people are such extortion artists!
They buy up all the competition and then set the price to the moon.
There is a law in the US against such criminal activity, but nobody in USG enforces it, b/c they’re all bribed into turning a blind eye. Anyways …
I found DX to be like using a primitive version of SW that doesn’t do too much and isn’t all it’s cracked up to be. Pretty sad.
If M2S had a few other functions, I’d pay the asking price.
But at this point, it’s worth only about $350 to me.


You guys ever use David 3D?


I got a demo of the SLS2 and worked with data coming from it. David has been aquired by HP see here.



Yeah, I know about the HP monopoly.
I’m looking for an older version before HP acquired it to see how good it is.
The entire metrology world has been monopolized by a few players, and it pisses me off to the point that I wish I could abolish the whole thing and start anew.
The only ‘brand’ that seems to be of any use in my mind is this:
But the price tag is WAY out of my reach!
Everything else is ‘rinky dink’ rubbish in comparison.