4

I am trying to mesh a point cloud, and calculate Gaussian and Mean curvature. I am using Meshlab.

I am trying to measure the average point cloud density, to be used in measuring curvature (APSS). The function "Radius from density" of a point cloud is confusing, and also does not include a read out.

Is there a way I can do this in Meshlab. Apologies - I am new to all of this.

Nakul
  • 51
  • 1
  • 2

1 Answers1

7

Here is the receipt:

  • compute radius as an estimation of the local density. To do this just type 'radius density' in the search box and choose the first filter. This filter computes for each vertex a value that is the average distance of the 'k' nearest neighbours (default k=16)
  • map the radius into the quality (type 'per vertex quality function' in the search box and choose the filter with that name. In the parameter func just type 'rad' and check the 'map into color' option. This filter will transfer the just computed radius per vertex value into the quality and will map this value into a standard rainbow color map.
  • type in the search box 'show quality hist' and choose (again :)) that option.

At this point you should get something similar to this...

enter image description here

ALoopingIcon
  • 2,218
  • 1
  • 21
  • 30
  • This is great!! Thanks a lot ALoopingIcon. This is exactly what I needed, a readout. One more questions - do all these quantities export as a dataset? Let's say I have curvature measurement on each vertex, can I export that as a matrix somehow? Again, thanks for this help! – Nakul Feb 08 '17 at 13:55
  • 1
    Do we know what's the unit of MinV and MaxV, and what does MaxC stands for? – Vineet Pandey Jul 24 '20 at 21:36
  • 1
    The units of MinV and MaxV are the same of the object coordinate. Most 3D formats do not have explicit units so MeshLab just use the values of the coordinates as they are, so if your object coords are expressed in mm all the subsequent measures done inside MeshLab will be expressed in that unit. MaxC is the maximum count of values in a bucket of the histogram. It is useful when you have to make multiple histograms with the same ranges and you insert manual values in the "Show Quality Histogram" parameters. – ALoopingIcon Jul 26 '20 at 08:56
  • Hi, do you know the exact algorithm used to compute this? In particular, what are the definitions of "radius" and "density" in this context? – ihdv Feb 01 '22 at 16:15
  • This filter computes for each vertex a value that is the average distance of the 'k' nearest neighbours (default k=16). This value was used as 'radius' of the splat in a old splatting algorithm, hence the name. Moreover this the inverse of this value is also a good density indicator (smaller the average distance of k neighbour higher the local density) – ALoopingIcon Feb 01 '22 at 17:02