Daniel: /* Procedure */

2015-02-20T13:19:44Z

Procedure

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= Menu =

This tool is accessible via the 'Tools > Fit > 2D Polygon (facet)' menu.

= Description =

This tool fits a 2D polygon on a point cloud. It's very similar to the 'Tools > Fit > [[Fit Plane | Plane]]' method but the extents of the fitted plane follows the cloud contour (in 2D).

= Procedure =

Select one or several point clouds then launch this tool.

For each cloud CloudCompare will first fit a plane and then extract the contour (in 2D).

CloudCompare will therefore ask for the 'max edge length' of the contour:
[[Image:Cc_fit_facet_dialog.jpg|center]]

This is the same parameter used for contour extraction in the [[Cross Section]] tool. If zero, the extracted contour will be the cloud convex hull. Otherwise, the smaller the max edge length is, the tighter the contour will be.

[[Image:Cc_fit_facet_example.jpg|frame|center|Fitted 'facet' (2D polygon)]]

In the console the following pieces of information will be output:
* plane fitting [http://en.wikipedia.org/wiki/Root_mean_square RMS]
* plane normal vector (with a positive Z coordinate by default)
* [http://en.wikipedia.org/wiki/Strike_and_dip dip and dip direction]
* a 4x4x transformation matrix that would make this plane horizontal (see the 'Edit > [[Apply Transformation]]' method to use it for instance)

Note: the fitted facet is added to the DB tree as a child of the cloud

= About facets =

[[Image:Cc_facet_db.jpg|center]]

The facet entity is a composite entity:
* the base 'Facet' entity holds some meta-data (the polygon surface, center and normal as well as the fitting RMS)
* it has a point cloud as child (the contour points)
* this contour point cloud has itself two children:
** the contour (as a polyline)
** the polygon (as a mesh)

Fit 2D Polygon - Revision history

Daniel: /* Procedure */