Grid and export without meshing


#1

HI - we are looking at solutions for point cloud editing.
Can the Hacksaw feature in Sequ’ grid and export a point cloud without meshing it.
We’d like to segment a point cloud into a grid of .ply’s.


#2

Not that I’m aware of. The “point region of interest” tool is designed to create subsets of particles that you should be able to export, but I’m no expert in the scripting API and I’m not sure if it’s possible to control the location and the export of those.

To go a bit into why Hacksaw doesn’t do this, Sequoia’s “Spatial PRT” stores particles in a way that’s efficient to look up based on a location and so doens’t need to split particle sets up. IIRC it will break the particle sets down into smaller and smaller sub-quadrants.

I’ll ask someone here what’s doable with the scripting API to see if there’s a way to build your export yourself.


#3

No, Hacksaw is specifically for segmenting meshes.

It might be possible to script the segmentation of a point cloud by creating a Point Region Of Interest with the size of a segment, moving it along X, Y, Z, and saving its content to individual segment files. But I have to check if all steps are actually scriptable.

Of course it can also be done manually by moving the ROI and hitting the save button again and again (but with hundreds of segments it would be tedious). I have done that in the past.

As Edwin mentioned, in Sequoia we tend to go the opposite way - we take many partial point files, and merge them into a single SPRT, since it is more efficient to load spatial regions on demand that way.


#4

OK - cheers Bobo,
I did look at creating ROI’s with script (briefly) and wondered if that was a solution.
What we are actually trying to do is grid a big Point cloud into different levels of detail - so it can run in Unity (VR).
I would be prepared to sit here and move the ROI - or create multiple ones etc. but I noticed that even when you Load a Fixed Level of detail in the LOD Mode - when you export that ROI it still outputs the highest amount of points, it doesn’t export the Level 0 amount of points. Is this correct - if so it would be a handy feature for our usage.
Thanks for the details - I shall continue my quest.


#5

This is correct, the LOD is only for OpenGL viewing, the saving and meshing always work with the highest resolution.
I am pretty sure I had asked for the ability to select an LOD for saving and meshing operations at some point, but my wish wasn’t granted.