Cross Section - Line & Graph tool

[Bradleysparkes]

Hi,

Firstly, thanks for an amazing piece of OpenSource software. It played a significant role in me completing my doctoral research and is proving very useful today for inspecting photogrammetry data for my new employer.

On that topic, it would be fantastic if there was an option to draw a line to plot cross sections in CC and easily compare two (or more) point clouds (to inspect registrations for example). Ideally this would include X & Y scales (whether this be absolute co-ordinates or local arbitary co-ordinates).

I'm thinking something akin to the profile tool in Quick Terrain Modeller if you're familiar with that, although appreciate that this is a tool in a paid-for piece of software.

Thanks,
Bradley

[daniel]

Well, in a way you can already extract the points along a line or a polyline (with the 'section extraction' tool). You can do that on both clouds (with the same line). Then the remaining gap might be to properly display/visually compare the results (especially if the result cannot be projected on a plane).

In a more limited way, you can use the Cross Section tool (or 'Clipping box') with the two (or more) entities selected. Then clip the points you want to compare - typically with a thin slice - and eventually hide the box interactors so as to only see the points (you can even set the view parallel to the cut).

cc_cross_section.jpg (70.84 KiB) Viewed 21809 times

[surda007]

Reading the topic now I can use the "extract cloud section" tool, which is one of the most useful for me. Thanks for that a lot!!
But it would be more efficient, if I could make the selections on more clouds with one line, and not just defining the section line one one cloud and open again and again on the others. Is it possible somehow?
And another question? Does the sectioning work on other than clouds, too? (Line, polyline, solids etc.)
Thanks very much!
Surda

[daniel]

I think that now both the 'Cross Section' and 'Section extraction' tools work with multiple clouds, don't they? (you'll have to use a recent version of course ;).

The 'Cross Section' tool works with meshes as well, but not for polyline section extraction.

[surda007]

Yeah!
It works!! I may missed something.
Thanks!!

[surda007]

I mean it works well with the extract section tool.
If I set just one cloud, but another is also open but not set, the cross section will affect just the set one, and not all of that.
But if I try to set more than one cloud for the "cross"section" tool, the button disappears.

[surda007]

And one more problem:
After making the sections on two clouds along the same (about horizintal) line I tried to transform one of the sections to make better registration. Of course I made it at "top view". The translation worked, but I couldn't rotate the section around the "Z" axes, just around another which tilted the section out of the section plane.
And after this, switching off the translate tool ang giong back to normal view, I couldn't rotate any clouds around all three axes by mouse, just around one axes vertical to the screen. Even if I swiched off all the sections and everything.
I may use wrong technique to register better the clouds by sections?

[daniel]

I'm confused. Which are you using here? The Cross Section tool? (then you have to use the colored torii if you want to rotate the clouds, and you have to move the mouse horizontally or vertically depending on the axis).

But in general I wouldn't advise using any manual registration. You can extract some slices if that's what you want to use as reference, and then apply a proper registration tool (Point-pair alignment or ICP). And eventually use the resulting transformation matrix (output in the Console) on the original cloud for instance.

[emmaird@hotmail.com]

I am selecting two clouds (overlapping clouds to see the changes between them) before selecting Extract Sections Tool, but Section contour ( with Vertices on) show only one line so I can't figure it out how it works. ( clouds cannot be identical due to processing) .

I have tried to upload both clouds here but it was an error for .xyz( invalid format) ( I am comparing a .las to .xyz). Thanks for any input.