Keep Best Line Data

[Admin]

Can someone shed some light on the Keep Best Line Data option.  Is it a permanent modification of the raw data?

Do any of you use it often?

[EFV]

The changes made by keep best line data shouldn't be "permanent."  As far as I know there should always be copies of the data saved to the workspace itself (under 3D digitized datasets in the workspace treeview).

As for the data in the align project, I can't confirm it right now, but the command EDIT RECOVER_DELETED_ELEMENTS should restore the data of selected scans no matter how the data was removed.  I know this works for reduce overlap, but I can't imagine keep best line data is any different.

I recommend using:

Code Select Expand


select all
edit recover_deleted_elements
select invert


This lets you see easily which elements were brought back by the operation.

As for using the function often.. well, whenever I have a project with lots of line scans (a lot would be several hundred to 1000+) and plenty of overlap I would use it.

The point, as I gather it, is to reduce the workload for IMMerge.  There shouldn't be a need for it if your merges go smoothly.

[PW User]

This function to "Keep the best line data" is only going to work if you have line scans (no white light) in an area that are both in the "right" orientation and the "wrong" orientation. Polyworks will detect the "wrong" orientation and keep only the "right" orientation.

Now, let me try to explain what is right and what is wrong.

A line scanner has a lot of density along the scan line, but each scan line is distanced more or less depending on the speed at which you move the scanner along the part. Let me call the two directions "scan line" direction and "displacement" direction respectively.

If you have a shape to scan that have a radius and flat areas around the radius, the best approach to scanning this and getting a good precision is to orient the scanner so that the scanner's line goes ACROSS the radius, not parallel to it. So each scan line has data on the radius, the shape's deficnition is along the scan line.

Now, on some parts, it's not alway possible to stay in the "right" orientation at all times, just think of two radii merging into each other, some scane passes will have the scan line parallel to the shape.

IMAlign, if it finds two scans overlaping each other in different orientation, will be able to distinguish the good one and remove data from the bad orientation.

Now this is not easy to explain in writing, so let me know if I have succeeded.

[Admin]

That makes sense to me.  Thanks.