Question

Clip Complex 3d Shapes From A Pointcloud

  • 21 April 2014
  • 3 replies
  • 16 views

Hi everyone,

 

 

I'm trying to take some complex 3D shapes and use them to clip a lidar pointcloud. Here's an example of the shape:

 

 

 

 

I need all the points that lie inside those cylinders places into a seperate las file. The 3D shapes are stored as a series of polygons with height attributes in a shapefile, I've been using the 3DForcer, then extruding them, then using the geometry coercer and aggregator, finally then feeding them through the clipper.

 

 

 

 

The problem is the clipper seems to clip everything above and below the largest polygon, as if it were 2D. Below is the result, as you can see it's clipping points outside the yellow cylnders which is what I don't want.

 

 

 

 

Are my shapefiles not truely 3D when I'm feeding them into the clipper? Should I not be aggregating them? I'm trying to clip trees out fo a forest, so whatever I do has to be batch processed 20,000 times.

 

 

Thanks a bunch!

 

 

-EAYREY

3 replies

I've used the 3DBoundingBox transformer and been able to create bounding boxes around each of my cylinders, then cut trees out with them. I'd still like to use the cylinders though. 

 

 

I've come to the conclusion that they're not truely 3d shapes being output by the extruder, but rather a collection of lines and polygons. Does anyone know how I can convert these quasi-3d shapes to a solid 3d shape that the clipper can use?
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hi eayrey

 

I've been struggeling with 3D clipping as well... Have you already tried to create some 3D clipping objects using the "creator" transformer? If it works with the objects created with this one, your 3D shapes don't have a geometry type the clipper is expecting (or can work with). Try to change the geometry using the "geometry coercer" transformer.
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Hi,

 

 

Maybe u can use the csg transformers, to convert the extrudes to solids?

 

The geometrycoercer, it has an fme_brep_solid output.

 

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