Correct Workflow

[Sean Withe]

Hi Daniel,

I'm completely new to CC and I'm trying to compare a scan taken in 2007 to a scan taken in 2016 to see how the object has changed.
I have "opened" my 2 scans and have them loaded in (1 is a pts and 1 is a e57, which may be where I'm going wrong already). Once in, I know I need to move them so they're sitting roughly ontop of one another, then run the align command/tool etc.
I have watched a couple of videos online and seems basic enough however I'm struggling at the first hurdle of simply working with the clouds. Pretty sure that the computer has the power and I have the latest CloudCompare v2.7.0 Stereo.
I'd be very grateful if you can help me out with a few pointers.

Kind Regards,

Sean
Formby Surveys Ltd

[daniel]

At which step exactly are you struggling?

Did you at least manage to select both cloud and start the 'Align' tool?

[Sean Withe]

sorry Daniel, I forgot to mention what my actual issue was. When I have both scans opened the software keeps going un-responsive with a spinning circle in the top left corner, which is making me wonder if I've missed a step in the preparation stages.

[daniel]

The spinning wheel only means that the LOD mechanism is in action (I guess one of the cloud is quite big?).

But it should definitely be responsive in this case (that's all the point of the LOD mechanism ;).

Do you have the same issue with only one cloud?

[Sean Withe]

Cloud sizes are 3.9gb and 5.7gb. Goes faster when working with only 1 cloud visible at a time however seems to be working a bit smoother now that I've started again. **I have trimmed the 5.7gb one down a bit inside CC.**

How do you propose I best go around moving the scans closer together? Currently following this video tutorial https://www.youtube.com/watch?v=MQiD4HjhpAU.

[daniel]

To register both clouds you should definitely use the Point pair based registration tool first (http://www.cloudcompare.org/doc/wiki/in ... itle=Align). I bet the things that are represented in both clouds must have changed quite a lot in almost 10 years?.

And of course before that you can make them closer just by calling the 'Tools > Register > Match bounding-box centers' before that if they are very far apart.

Once you have registered the clouds at least roughly with the Align tool, you can also call the automatic refinement tool (ICP). But pay attention to the 'overlap' parameter is the clouds are quite different from each other.

Last but not least: if your clouds are huge (you can look at the number of points in the clouds 'Properties'), you can also decimate them with the 'Subsample' option. Then work on the decimated versions. And eventually apply the final transformation matrix to the original cloud (see http://www.cloudcompare.org/doc/wiki/in ... on_history).

[Sean Withe]

Hi Daniel,

That's great thanks! I'm going to try all that this afternoon and hopefully get a result. If I have any more issues I will just add them onto this thread but you've gave me some very clear and helpful tips there!

Regards,

Sean.