Trimble Business Center

Is there any way we can create a break-line extraction tool for point clouds? I recently had a bridge scan that i needed to create top of deck surface as well as a bottom of slab surface and parapet walls to compute volumes. Having to go through and manually create the gutter lines and back of parapet walls was time consuming. I know there is the point cloud smart picking mode that somewhat works, but i think it needs to be refined as it did not seem to be any faster than drawing the 3D lines myself. Topodot has a break-line extraction command that works much better for this. Even if we could place vertices or points inside the cutting plane view i think would help out tremendously. Is there a command or workflow that TBC already has that can help with this? If so, please let me know.

Thanks!

#enhancementrequest

I did an exercise at PUG last year on this - what I found was the following - and while not an automatic extraction of features it did provide very good results.

1. I used the Cutting Plane View with an alignment to create many cuting planes across a bridge structure with barrier walls
2. In the cutting planes I draw sections using snaps in the point cloud to create Top of Wall / Bottom of wall etc - I use a Polyline not a linestring as a Polyline is 2D only and draws in the plane of the Cutting Plane and creates a perfect 3D line in 3D space (it has a UCS in the plane of the cutting plane).
3. Once I have the sections at each station, I draw in the lines between the sections for the features that I want - we are adding a feature command today that will find edge lines between lines in 3D view that I hope to have drawing between common nodes in adjacent sections (for many nodes at one pass) - I have not tried the tool yet with UCS based objects - this is a good example of where this could be used also - That command will be in the next TBC release I hope.

I did also try drawing directly in the point cloud in the 3D view - I have found that if exaggerated the draing in 3D view fails to work correctly, but at 1:1 it appeared to also work well and to a large extent I could draw fearture lines pretty accurately directly in the point cloud.

I know that everyone wants automatic feature line creation, and I did take a god look at the Topodot solution, and I felt that the 1-3 approach was pretty similar to the Topodot approach with a couple of exceptions and it did work pretty fast in TBC. This is an area the team is looking into and I hope we will see results at some point.

Alan

Thanks Alan! I was unaware that polyline worked in cutting plane view and not linestring. That definitely will help me out now. I look forward to seeing the upcoming releases.

Linestring works but because a Linestring is 3D it will snap to points in

the Point Cloud that are in the depth of field of the cutting plane - and

it will not be at the Station of the Cutting Plane - the Polyline because

it is 2D and a Fixed Third Axis - when drawn in the Cutting plane will be

drawn only at the plane of the cutting plane (that is the Z axis in a

Cutting Plane) - so it is like drawing a section in the station plane -

whereas Linestring doesnt work as well because it wont stay on section

unless your depth of field is almost zero

An idea that you may want to try - This works pretty well I think and may

help you out here

1) Clean your point cloud to remove noise

2) Create the HAL for the road

3) Create Cutting Planes at say 10' stations down the road alignment

4) Use the cutting plane view with a depth of field of 0.5' or 0.25' (keep

it narrow but wide enough to get sufficient data) and then select the

points that make up the surface at each cutting plane that are displayed

using Poly Select or Rectangle Select - and add the strip of data to a

Point Cloud Region

5) When you have all the sections / cutting planes done, make a surface out

of the points in the Region you created - use as many of the Total points

as possible to get the best surface shape at each section

6) Label the HAL with Station Labels every 10' that have a Tick Mark Length

wider than your road

7) Use the Change Elevation command to "Drape" the Tick Marks of your

alignment labels on the surface you created

with a 0.25' width - on a single side Bridge deck - sections every 10' for

~200' of deck generates a Region of ~1.4 million points

These are now sections through the surface at each station and you can then

draw longitudinal features through the sections etc.

Here are the sections I created

And then the long features through the sections - as you know this is not a

precise science

I use this technique a lot on Road Jobs

Alan

On Thu, Sep 5, 2019 at 7:08 AM mkohler@kapurinc.com <trimble@jiveon.com>

Alan, that process you described is exactly the right idea. Civils will trace the horizontal of things like curbs, first. Then they extract the vertical from the point cloud. At least that is what they want. Progs that pick point to point are very limited, as you get wandering 3d linework when trying to follow a known regular edge. My suggested solution is make a tool that selects all point cloud points some dist to left or right of an alignment or linestring, and crunch them down to a best fit profile. Then project that to the linestring and you have your breakline. I'm writing that myself but that step of selecting all points to left or right is not trivial. Your tools can easily do that. Its not all automatic, but its the right way to get breaklines along things like curbs or road edges. You don't want points on the side that drops down like a curb face, you want them on the side that is more or less flat to the edge. Whoever gets to that tool first will have a leg up on everyone else.

Alan,

I could really use this.  Any chance of a short video for us old guys??

Bruce Flora