CloudCompare forum

hello,

I performed an alignment (translate + rotate + scale) of one cloud (drone based) to a reference cloud (terrestrial lidar based). Now, I would like to apply that same transformation to another cloud (the first drone cloud i was working with was cropped, but now want to apply that same alignment to the entire uncropped drone cloud). I saved the transformation matrix from the alignment, but when applying that transformation to the entire drone cloud, it doesn't seem to line up where it should. Any suggestions of where I might be going wrong?

Also, it's a bit confusing as to what to do when CC asks me if it wants to me shift the points of the rotated clouds upon import - i assume not. All my points are saved as .laz (unfortunately i didn't save the .bin's).

thanks,
allie

matrix:
-0.365898460150 0.486379295588 0.003565789200 -14.168521881104
-0.486216425896 -0.365636259317 -0.019050257280 24.160911560059
-0.013081117533 -0.014300752431 0.608344972134 24.582180023193
0.000000000000 0.000000000000 0.000000000000 1.000000000000

Hello, allie

I'll try to reply you with help of small example step by step:

1. open data file (open pit in my example).
2. cut a piece and shift/rotate it (in your case you aligned it by registration)
3. please note that after this procedure the matrix will appear in console.

4. please select this matrix in console and press Ctrl+C
5. select another part of cloud remaining in old position and select menu Edit -> Apply Transformation (or Ctrl+T)

6. In my case the matrix is in clipboard now (you can click [ASCII file] to select your matrix from the file), so click on clipboard button.
7. Your matrix will appear in the dialog. Just click Ok.
Profit:

I think there are a couple of things going on here:

First, if CC asks you to shift the points, maybe you have an already georeferenced point cloud. To put it briefly, this is usually problematic because of the way 3D computer graphics works (you can check the CC documentation on the Global Shift tool for more details). If that's the case, you should probably shift the cloud so the coordinate numbers of any point aren't too large (like x = 1000000, preferably keep it in the thousands).

After that, redo your alignments and check the results.

Also, can you describe how are you applying the transformation of the first chunk to the second?