Removing original surface points when smoothing the surface

[Anonymous]

Hi, I would like to smooth an AutoCAD Civil 3D surface to specified grid intervals, but would like to remove the original points from the surface to leave the uniformly spaced grid of surface points.  Currently, when I use the surface smoothing function, it adds the grid points to the existing surface and retains the original points.  I would appreaciate any help to find an easy way to accomplish this.

Thanks!

Amanda

[neilyj666]

I'm curious as to why you would want to do this as you could lose considerable accuracy in your surface?

Not sure it can be done as the original points are used to determine the smoothing and when they are removed the surface has no information so the smoothing will fail.

[neilyj666]

If you must do this then I'd use the Create points from surface option and create a new surface from the derived points

[tcorey]

Export to DEM (GeoTIFF format) allows you to pick a grid interval.

Import the exported GeoTIFF using Create Surface from DEM.

[Joe-Bouza]

Always room on the belt for more tools

[Anonymous]

Hi tcorey,

Great suggestion, but when I bring the DEM back into a new surface, it is in grid format and I need it to be in a TIN to extrude to a 3D surface.  Any thoughts?

Thanks!

Amanda

[neilyj666]

My original comments still apply to this method - unless you are extracting points in a VERY closely spaced grid your surface is not much use for anything apart from visualisations - perhaps this is what you are doing?

[Joe-Bouza]

Hi Tim

I gave that a try. My sample surface was small and the export took along time (overnight), and the subsequent import is locking up the machine. I left the refault spacing at 1 foot; perhaps this is why?

[doni49]

1) I agree with neilyj on this -- doing this will reduce the accuracy of the surface and IMHO that's rarely (if ever) a good thing.

2) If you want the surface to triangulate to ONLY these grid points, then under the Point Creation tools, use the Create Points on a Grid tool.  It will allow you to specify the grid spacing and each point will be placed such that the point elevation matches the specified surface at that location.  Then you can turn around and create a new surface that uses ONLY those points.

[Anonymous]

Hi Neilyj,

I agree that the accuracy will be reduced.  I am trying to make an STL file from ground-based LiDAR data for numerical modeling.  The LiDAR data is VERY dense relative to the size of the area and there are just too many data points to do this process in AutoCAD without simplifying the surface (AutoCAD will just crash).  I've found that the options for simplifying the surface just don't work well for maintaining the shape and I get clusters of several points in small areas trying to maintain accuracy but compromising accuracing in larger areas due to the nature of the LiDAR data. I would like to use a dense grid to reduce the total numer of points.

Thanks,

Amanda 

[tcorey]

If you simply want to reduce the number of points, don't care that any accuracy algorithms won't be applied, you can create a point file format that only reads every Nth point. The setting in the image would reduce the file size by ninety percent.

[neilyj666]

No idea what an STL file is or what it is used for....;)
How big is the area you are trying to model?

[BrianHailey]

I've not investigated the command much but there is the Simplify Surface edit that might do what you want it to.

[mthales16]

I have the same question as coxal (Amanda).  When using drone or LiDAR point clouds, the data is so dense that it is almost impossible to use without crashing AutoCAD.  There are several ways to simplify the surface that I have found, but it would be nice to know if someone has found an more effective method.

With the smooth surface command, the points are added to the already point-saturated surface.  The simplify surface command has been somewhat helpful, but creating points on a grid has been the best option so far that I have seen. Unfortunately, the points must be grouped and then added to a surface which can require a lot of time.  Exporting to a DEM file only allows it to be brought back in as a grid surface as far as I can tell.  If anyone knows of another method to quickly add points to a TIN surface on a grid while eliminating the existing points, please do share.

Thanks,

Matt

[BrianHailey]

Hi Matt and welcome to the forums.

I would recommend checking out InfraWorks. There are new tools in InfraWorks that allow you to create a surface from a point cloud. It will automatically weed out your points for you and, alternatively, export out a new point cloud with just the points used for the surface creation. When the surface has been made in InfraWorks, you can open the InfraWorks model in Civil 3D and import the surface for use in Civil 3D for your design.

[TerryDotson]

... quickly add points to a TIN surface on a grid while eliminating the existing points ...

DotSoft's Free Civil3D Lidar Tools

We have added Tin/Grid surface export to LAZ file, using all points or sampling on a user specified interval.  So use the LIDARMAKE tool to create a temporary LAZ file, then LIDARTIN to create a new TinSurface from it.  Also added:

• LIDARTHIN to weed a file using various filters (creates a new file of course).
• LIDARPLOT to plot a window of dbPoints from a Lidar file (cautions included).

The contour filter on the thinner is interesting if all you want is to show contours.  It removes points beyond a tolerance of specified contours, our testing shows sometimes using only 2% of the original points can create roughly the same contours.

Use caution and always retain your original surfaces and lidar files !!!