Discussion Groups

*Expert Elite*
Posts: 2,292
Registered: ‎07-09-2003

# Point Cloud for Civil 3D

481 Views, 3 Replies
03-21-2011 10:34 AM

I have two questoins:

1. If I have a point cloud that contains 10 million points, how many will the point cloud object actually use?  I have heard 1.5 million.  I ultimately need to add all 10 million to a surface.
2. In Civil 3D, we have a "Simplify Surface" tool.  it has some options for "decimating" the surface.  The new Point Cloud "decimation" video simply shows the same slider we get in Civil 3d 2011 without this new add-on.  Is this slider different in this new tool?  I'm wondering if someone can explain the algorithm used for this decimation process.  How does the software decide which points to remove?  Also, does this algorithm resemble Civil 3D's Simplify Surface tool?

Thanks.

Matt Kolberg
Cansel - Autodesk Division
http://www.cansel.ca/
Employee
Posts: 12
Registered: ‎12-22-2010

# Re: Point Cloud for Civil 3D

03-23-2011 01:52 AM in reply to: mathewk

1. Actually there are only 0.8 million points used for feature extraction.

2. The 'Point Cloud Decimation' acutally exports the selected displayed points. The video shows that 'Export' tool can be used for point cloud decimation. There is no complex algorithm behind it. The decimation is based on the density adjustment.

New Member
Posts: 1
Registered: ‎05-17-2011

# Re: Point Cloud for Civil 3D

05-17-2011 01:07 AM in reply to: mathewk

Hello,

I have a question that stems from this.

I have created a surface from LIDAR Data using the point cloud tool and have found that the surface does not match the contour panels provided well enough for the surface to be used in design, Is there is no way for me then to increase the density of points used in creating the surface?

If so, would the best way to work with this amount of information be to decrease the total number of points in the point cloud item by creating several files and making surfaces from point cloud tool for each one?

Best Regards,

Anton

Employee
Posts: 12
Registered: ‎12-22-2010

# Re: Point Cloud for Civil 3D

05-18-2011 02:02 AM in reply to: mathewk

The inaccuracy might be caused by improper setting of the parameters used for ground filtering. You can try to adjust the paramters according to the guide in the 'Getting started' document.

If it is really the problem of the point density, I am afraid partition the file into several smaller ones is the current solution.