smoothing

[Homer-Jay]

Can anyone let me know how to run smoothing on a point cloud without it splitting apart into a million pieces

[jrayself]

Not sure what you mean by splitting it into a million pieces.  Can you describe your current process?

[Homer-Jay]

i'll run a series of scans. align the part using the best fit. then when i have what i consider to be a good full point cloud, i'll right click in the tree and select: edit ..  smoothing. and the part kind of comes undone. almost like all of the scans come unglued. like Neo dodging bullets lol

[jrayself]

You align the scan to a reference model using best-fit or you align the individual scan passes to themselves using best-fit?

[Homer-Jay]

to themselves, I'll lock the first group of scans align my other groups to them

[jrayself]

Anyone else feel free to jump in, but I never understood the concept behind aligning the individual scan passes to themselves.  If the part was scanned from one position then why align the images and rick modifying the actual shape of the part.

I get if it was scan data from a spherical grid scanner in several different positions, but not an arm and scanner.

[Homer-Jay]

in this case i dont have a reference model. i'm scanning a part to export as an stp file for machining. i'm putting it on hold  until i get some more training. should be going the 25th. i've had better luck with other parts. this one in particular is very narrow, and i have to get the edges right.

[tobiwan]

the Images -> Smooth Filter is quite agressive, at least i its standard settings ;)
better try a few times with different settings before using it and alway check the "Minmize data loss..." checkbox. Be aware there's no Undo for the filter...

Its actually the same filter as in the scan pass smoothing you can apply during the scanning process.
Personally, I only use the scan line filter  (SIM Filter) dureing scanning and do the rest of the filtering in IMEdit, or while merging.

[Homer-Jay]

i'll try these things the next time i fire up the scanner

[PW User]

Hello,

Smoothing within IMAlign is very aggressive indeed. What is your scanner (which brand and model)? What are your scanning parameters (Interpolation step and max distance)? When you aligned in IMAlign, you must have had a standard deviation calculation done over your scans... do you have a ballpark figure for the STDDEV?

It is rare that you need to smooth within IMAlign. What is your ultimate goal? You said you want to send an STP to machine.. Do you mean that you want to create surfaces in IMEdit and then export them as STEP to use in a CAD/CAM package and eventually manufacture using those surfaces?

If that is the case, then I recommend NOT to smooth within IMAlign.

In the process of reverse-engineering (this is what you are doing) you will create a polygonal model (by making your IMAlign project go through IMMerge and be transformed from a point cloud to a skin of triangles). In IMMerge, there will be smoothing available there (although you do not want to be too agressive there either).

After creating your polygonal model, it is possible to smooth within IMEdit. If you want to smooth the low curvature regions with a more aggressive value than the high curvature areas, you can use an advanced selection based on curvature and apply a different radius of filtering based on you selection.

It is an advanced way to smooth you scans that will treat high curvature areas (where there is a lot of shape like sharp edges and tight radii) differently and may give you a much better result overall.

If you plan on making surfaces and then export them to your CAD/CAM package, the fitting of surfaces also has a "smoothing" that can be applied. It's in the "Custom Fit NURBS Patches" that you have access to a "Boundary tolerance". If you bring up that value, you will see your curvature changes decreased, effectively smoothing the resulting surfaces. This is also an advanced way to "smooth" stuff before sending it to your machining software.

All this to say that you have other means of smoothing, not only the "smooth image" command in IMAlign.

Let us know what your plan is. If you are going to a training session, these advanced methods can be discussed at the end of the basic training material, there is always time for discussions on best practices and more advanced techniques at the end of training sessions. But you must first master the basic workflows before attempting to control advanced techniques... I never saw a good result when a 2 year old tried to run before learning how to walk...

Once you master the technique for walking (basic techniques show in the basic training), then you are ready to learn how to run (advanced techniques).

[Homer-Jay]

i am creating surfaces to export as step for machining. the reason i was trying to smooth my point cloud, is that my polygonal model will often have voids that become very coarse when i use the automatic hole fill. so i reasoned that i had to have a perfect point cloud to start with. i am holding off for a while, until training. hopefully they'll send me this month. i have a fairly good command of the hard probing, and my machine castings are mostly inner diameters, bores, and holes anyway. i will however, get the laser out, and try some of the methods you all have described. thanks for the advise.

[Homer-Jay]

i have already created a much better polygonal model by not smooting in align. i'm going to play with the custom fitting of nurbs patches and see if i can get a grasp on that

[Homer-Jay]

btw its a romer, and perceptron. by not smoothing in align i have already made much better models. even learned to take it through to nurbs, and export it as in iges, so i could try probing with a reference. i better work on my alignments in inspect though, because i was way out of tolerance probing the same model i scanned lol. no but seriously.. i was just practicing, and didnt fixture it well, so i'm sure it was moving as i was probing it. My points and sharp edges are atill a little rough, but i have some ideas, like making sure the part i want to reverse engineer has clean edges, and also learning ways to cope with it in the software as well. sucked to have to reverse engineer a part to have a reference for probing. one of our main customers is finally going to provide us with 3d part files to use. and i needed to scan the part anyway,  because we're going to machine a mold to produce them

[pkh6688]

I think if you need to check the dimension, better don't smooth the scanned data. I tried compare a smoothed data and unsmoothed data, and found the smoothing will affect the dimension checking.