Page 1 of 2

wrong area and volume (larger convex hull)

Posted: Mon May 25, 2020 4:35 pm
by DA523
I am trying to find area and volume of simple XYZ points
I got wrong area because convex hull code make larger perimeter with out any way to correct the hull manually (segment tool does not help)
I can get nice hull with QGIS very easily
but I want same hull result in CC for correct are and volume
please help
how to get same hull in CC or how to modified manually before calculation?

Re: wrong area and volume (larger convex hull)

Posted: Mon May 25, 2020 9:38 pm
by daniel
How did you generate the 'hull' here?

And what are these white points? (there are not a lot ;)

Re: wrong area and volume (larger convex hull)

Posted: Tue May 26, 2020 12:00 am
by DA523
hulls is generated by CC prior to any 2.5D volume calculation or even mesh
but as you can compare with hull by QGIS
CC hull is larger and can make area and volume +20% ore more (stockpile calculation)

Re: wrong area and volume (larger convex hull)

Posted: Tue May 26, 2020 12:10 am
by DA523
here I attacked example

Re: wrong area and volume (larger convex hull)

Posted: Tue May 26, 2020 12:13 am
by DA523
I think forum can only attach one image per post

Re: wrong area and volume (larger convex hull)

Posted: Tue May 26, 2020 12:48 am
by WargodHernandez
Are you expecting CC to produce a concave hull? I thought we only have convex hull generation. That would explain the difference

Re: wrong area and volume (larger convex hull)

Posted: Wed May 27, 2020 6:46 am
by daniel
Well, my question was really "how" did you generate the hull? With the 'Edit > Fit > Facet' tool?

Because there's a way to generate a concave hull, but not as a polygon. And mind also that the 'Facet' tool doesn't generate a flat polygon, but a 2.5D one.

Anyway, I agree with Chris, here it definitely looks like a convex hull, and not a concave one.

Re: wrong area and volume (larger convex hull)

Posted: Wed May 27, 2020 5:40 pm
by DA523
OK it clear to me the difference between convex and concave
so how to tell CC to use concave not convex to calculate area and volume?
because it is more accurate to use concave
The goal is stockpile volume calculation

Re: wrong area and volume (larger convex hull)

Posted: Fri May 29, 2020 8:17 am
by daniel
Well as I said that's not possible for a mesh or facet.

Re: wrong area and volume (larger convex hull)

Posted: Fri May 29, 2020 5:48 pm
by DA523
OK, that means CC is bad choice for any volume calculation.
2.5D volume or mesh volume is misleading and must be avoided for any real application.