View source for Unroll

== Menu ==

This tool is accessible via the 'Tools > Projection > Unroll' menu.

== Description ==

This method 'unrolls' a point cloud from a cylindrical (or conical) shape onto a plane:

[[Image:Cc_unroll_input.jpg|frame|center|Cylindrical shape to unroll]]
[[Image:Cc_unroll_result.jpg|frame|center|Cylindrical shape unrolled]]
[[Image:Cc_unroll_cone_example.jpg|frame|center|Unrolled cone]]

== Procedure ==

Select a single cloud then start this tool.

=== Cylinder ===

[[Image:Cc_unroll_cylinder_dialog.jpg|frame|center|'Unroll cylinder' dialog]]

Main parameters are:
* axis of revolution (X, Y, Z, or a custom 3D axis)
* cylinder radius
* optionally a point on the axis (''otherwise CloudCompare can try to guess it by computing the gravity center of the point cloud'')
* since version 2.11, it is also possible to specify the angular range. By default it's [0-360], but you can input any angular value, and even multiple revolutions.

Most of these parameters can be populated by choosing an existing cylinder primitive already loaded in the database.

[[Image:Unroll_angles.JPG|frame|center|'Unroll angular zero and sign' dialog]]

=== Cone ===

Since version 2.9, this method unrolls a cone in a way that preserves surfaces (as if the cone was 'rolling' on a planar surface).
And since version 2.13, a sub-option 'Projection' allows to choose the type of conical projection among:
* Conical
* Cylindrical (fixed radius)
** this mode corresponds to the old 'Cone' unrolling mode in version 2.8 and prior. It unrolls a cone-shaped cloud as if it was a cylinder, by first 'straightening' the cone walls.
* Cylindrical (adaptive radius)

[[Image:Cc_unroll_cone_dialog.jpg|frame|center|'Unroll cone' dialog]]

Main parameters are:
* axis of revolution (X, Y, Z or a custom 3D axis)
* half angle (this is the ''aperture'' angle at the cone apex) in degrees
* the cone apex position in 3D
* span ratio
* start and stop angles

Most of these parameters can be populated by choosing an existing cone primitive already loaded in the database.

== Export deviation scalar field ==

A checkbox named 'Export deviation scalar field' allows to compute for each point its radial distance to the theoretical unrolling shape (cylinder or cone). A new scalar field will be added to the output cloud.

== Output unrolled cloud in an arbitrary coordinate system ==

Since version 2.13, it is now possible to output the unrolled cloud in an arbitrary coordinate system:
* X: unroll angle
* Y: distance to primitive
* Z: longitude