HullReplacer should do the trick.

http://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Transformers/Transformers/hullreplacer.htm

​@kowfoz1​  

I have uploaded a simple workspace that may help.

You simply add the Point Cloud dataset; filter the buildings using the 'PointCloudSplitter' transformer if that is the layer you require, in this case classification = 6; Convert the point cloud to points using the 'PointCloudCoercer' transformer; Buffer the points so that the points overlap the other point features. in this case I buffered the points creating squares; and lastly, I smoothed the polygons using the 'Generalizer' transformer.

Thanks. WHat is the difference between HullReplacer and HullAccumulator exactly?

• The HullReplacer creates a hull (convex or Concave) for each individual feature.
  • 5 lines/points = 5 polygons
• The HullAccumulator creates a hull (convex or Concave) for each feature set.
  • 5 lines/points = 1 polygon
  • Attributes can be gathered into a list

You may need to use the accumulator if you deaggregated the cloud into individual points. It should already be a single aggregate feature so you can use the HullReplacer.

Thanks.

So would I be right in saying the bufferer actually gives the more accurate outline? As I actually want the more exact outline rather than a smoothed outline? See image attached

at the moment I use Hullreplacer which actually gives too smooth a result

Can you help?

I see what you want to do. Buffers work but it looks terrible so you have to clean them up to look smoother. The attached workbench creates a randomized set of points to demo how this works. You will need to adjust the buffer sizes to match your units.

Workbench - Attached .fmwt

Points with a buffer end up with ragged edges

Stroking the arcs of the hulls and buffering creates a cleaner outline

That is a great help. So now I have the image below:

The buffer lines are quite thick though? How do I make them more like just lines connecting the dots of the original point cloud? Image below:

Adjust the negative buffer amount on the last Bufferer until you get the desired result. For example, if you change the example to a -2.4 it will almost be on the nodes.

Play around with changing all three of the bufferers to get a better idea of what it's doing. There's going to be a combination between those three that should be very close to what you want.

when you say negative buffer..... Which element below?

I tried -0.08 instead of 0.08 but then there is view displayed?

Buffer Distance can be positive or negative. A positive buffer will buffer outward and a negative will buffer inward.

In the example workbench, only 1 buffer should be negative. Marked below.

There are 3 bufferers in the example process I sent.

1. Bufferer = Initial buffer of the points to create overlapping polygons for dissolve (positive)
2. Bufferer_3 = Creates the rounded edges from the hulls (positive)
3. Bufferer_2 = Shrinks the polygon back down to the original size (change this one to negative)

Bufferer_2 can't be less than the sum of Bufferer + Bufferer_3 or the polygon will disappear because you buffered it out of existence.

So, if I have;

Bufferer = .6

Bufferer_3 = 2

Bufferer_2 = can be any value up to -2.6 without losing any data. If you go beyond 2.6, it may or may not buffer polygons out of existence depending on how many polygons were dissolved together.