Laser scaning to 3D model

Data collection by the scanner is super accurate, much more accurate than what is needed. The problem is that the normal naval software that transforms those points on the surfaces of the hull, generates surfaces that do not pass through these points.

 

Hi All,

Some years ago we did repairing work for replacing double bottom and outer shell for chemical tankers. We also use 3d scanning and recreate hull surface of this old vessel from points cloud. We did it manually in our software. We agree with shipyard about deviation 3mm from original points. Finally everything fit very well, but I dont know any software for automatically recreation nurbs surface from points cloud. I have seen some publication about it in literature, but this is just academicals research and without any real success.

 

You can do this with most photogrammetry software.... After you have your densified point cloud and surface mesh, you should be able to take slices through it and export each slice as a 2D dxf file or similar.

Once you have a whole set of 2D slices, and they could be either waterlines buttock lines or transverse slices, then you could bring these into any naval architecture package to do the hydrostatics as most of these packages slice up the 3d model before processing the hydros anyway? The resolution of the slices is not that important for hydrostatic calcs anyway no?

Otherwise , most photogrammetry software will export a 3d *.obj file or similar directly, provided the NA software will import it- you have your accurate and true to scale model directly with surfaces already built.

 

One of the problems encountered is that, depending on the type of polimeshes created, some softwares are not able to obtain slices.

 

All of the pro photogrammetry software I've seen has the ability to take slices. It's commonly used for volumetric analysis in Geo technical industries. Is there much of a market for ship surveying in this manner? I don't mean as a class surveyor etc but rather to offer services for accurate spatial surveying inside and out where extremely accurate measurements can be made during building or modification of ships to verify construction progress is accurate or other related information delivery where access is difficult or where large amounts of spatial information can be collected and delivered more efficiently. Its something I'm interested in getting involved in as I'm already doing it for ground survey purposes...

 

One thing is to have extremely accurate measurements and something else, very different and very specific problems, is to create a surface that faithfully reproduce the scanned object (which is exactly like the model, not very similar) and is manipulable by CAD softwares.

 

Not really no.....only to button pushers and armchair designers though perhaps.

When I compare the method I use to calculate hydro's from when i was a student and a newbie at work to now..chalk and cheese and the level of accuracy that was "acceptable" then is so much lower than what is achievable today.

The key thing of course is a quantitative procedure and verification of the software producing correct results. That's it really.

 

The software i use generates a quality report for every project. It computes the uncertainties for all inputs , allows opportunities to improve those uncertainties and gives good feedback as to potential error of every point generated, it's generally very good but does take considerable experience in order to achieve good results as per the old gigo saying...

Would it be useful to naval architecture - a highly accurate 3d model of the ship, part built to monitor progress, check measurements, measure discrepancies, measure volumes etc of the actual structure as it stands at that instance. A huge amount of information can be gathered on day 1 and delivered on day 2 using photogrammetry which also negates any access problems and improves safety gathering this info. I'm sure there must be people already doing it in the ship building industry?

 

groper, for many years the "reverse engineering" is used in shipbuilding. It is not necessary to discover the wheel. The acquisition of information is a totally refined technique and perfectly used in shipbuilding/shiprepair. The problem with boats is that hydrostatic calculations, and similar calculations require a much greater accuracy than those required in other engineering disciplines. The surfaces model obtained from scanned points must accurately represent the hull. And that's where the difficulties begin. All the above process, geting data/points, is controlled and no longer worry anyone. What the OP is asking, for days, it is how to move from points to a NURBS surface, manageable with a CAD program. Unfortunately poly meshes, which is the most accurate and easy to get, are not always useful.

 

For about 5 days we succeed to create 3D of ship, which we scan. Model is not perfect, as we don't have much expirience in surface modeling, but is closed enough to be used for calculations ( mostly small diferences in shape of bow ). But the original idea was to receive directly this 3D model from scans points ....

Gropper, what software do you use to compare point cloud and 3D model?