Sampling points / overlay point matrix

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cloudmaster
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Joined: Wed Mar 12, 2014 1:13 pm

Sampling points / overlay point matrix

Post by cloudmaster »

Hello, I want to know if it is somehow possible to put a point matrix on the top of a point cloud. If we for instance have a half ball as a point cloud then I would like to make a matrix of points with a specific distance between the points in both x and y. (the matrix can be 50 x 50 points with 1 cm distance) that cover the whole ball.
I have tried to use the function "Subsample a Point Cloud" > Spaces....but in here I can not specify it accurate enough. After I have got the correct point matrix I need the xyz information to reproduce the ball in another software.

Is there any solution to this, how this can be solved?

Thank!
daniel
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Re: Sampling points / overlay point matrix

Post by daniel »

I think the "Tools > Projection > Rasterize (...)" tool is what you're looking for.

Or did I missed something?
Daniel, CloudCompare admin
cloudmaster
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Re: Sampling points / overlay point matrix

Post by cloudmaster »

Thanks a lot, that is the right function I was searching for!

Is it possible to specify the area this matrix should cover of the point cloud? and also the position of the matrix, so I for instance get a line of points in the center of the ball (center goes from the highest point on the ball)?
daniel
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Re: Sampling points / overlay point matrix

Post by daniel »

You can edit the grid extents in 2D (with the 'Edit grid' button) but I guess you already found that out?
Daniel, CloudCompare admin
cloudmaster
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Re: Sampling points / overlay point matrix

Post by cloudmaster »

Hello,

I see that option to edit, but cant get it to work as I want.

I would like to specify exactly where the center line in my point cloud object is, so a line of point in the grid matching the center line of the object.
How is that possible to do?

Another question I have if I use the segment tool on the new grid I make, is it then possible just to save / export the points again, without do a new "Grid generation"?
daniel
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Re: Sampling points / overlay point matrix

Post by daniel »

To make what you want you'll have to do some maths I guess.

And otherwise, you can of course export any cloud anytime by selecting it and using "File > Save". Or have I once again misunderstood you? ;)
Daniel, CloudCompare admin
cloudmaster
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Re: Sampling points / overlay point matrix

Post by cloudmaster »

OK, I was just hoping that there was an easy way to tell the software where I would like the grid to start. Maybe I just have to work a little more with it.

About the saving, I don't get the same CSV/txt file when I do save it in File > Save, here I only get the CSV file as a point cloud. What I was asking about was how I could save the "grid points" depth with my specified distance in txt file after I have done a "segment" on the grid.

Now another tricky question came up: is it possible to specify how the points in the "grid generation" coming into excel. At the moment I have to turn the grid in Excel 180° degrees to get it in the right way for further processing. Can CC help with that?
daniel
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Re: Sampling points / overlay point matrix

Post by daniel »

Ah ok, this way to export the grid as a matrix is indeed only available in the "Rasterize" tool. It has been coded long ago so it's fairly simple. There's no option to transpose the matrix.
Daniel, CloudCompare admin
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