.. _segmentation:

Segmentation
============

.. _SegmentationFIG:

.. figure:: /img/Segmentation.png
   :width: 400
   :align: center

   Segmentation panel


The Segmentation panel is centered on cutter-based splitting workflows.

.. _segmentation-cutter-set:

**Cutter set + m2**

- *Cutter set* generates a cutter grid based on the active mesh extent and the selected square meters value (*m2*).
- Before creation, if the active object scale is not *1,1,1*, the tool shows a warning popup and can apply scale automatically.
- Generated cutters are organized in the root collection named *_cutter*.
- Cutters are moved to *_cutter* (not duplicated in the source object collection).

**Cutter availability**

- The panel shows the number of cutters currently available in scene.
- A *Delete all cutters* command removes all cutter meshes from *_cutter*.

.. _segmentation-cut-modes:

**Multi-cutter / Mono-cutter**

- *Multi-cutter* (main workflow): the active target mesh is cut by selected cutter objects; if no cutters are selected, all cutters available in *_cutter* are used automatically.
- *Mono-cutter* (advanced workflow): one active cutter mesh projects cuts on selected non-cutter meshes.

Both modes are enabled only when cutters are available.

**Pre-cut topology check**

Before segmentation, target meshes can run a basic topology cleanup (merge/remove doubled vertices) to reduce knife projection issues.
The panel includes a toggle (*Topology pre-clean before cut*) to enable/disable this step depending on model quality and performance needs.


..
   This panel (:numref:`Fig. %s <SegmentationFIG>`) allows to use a set of tools to segment a 3D object in tiles.
   This procedure could help user to manage both the texture phase (outside of Blender) and the LODs creation of a high-resolution 3D object (such as, photogrammetric dataset or 3D scans).


.. admonition:: Remember

 Before using this tool, it’s necessary to control the scale of each 3D object that must be segmented.
 To control the scale of a 3D object it is recommend to check the scale value in the *Scale* panel, located within the *Item* tab, on the *Sidebar* of Blender.
 If the 3D object is the result of a 3D survey, it must match its real dimensions.
 If the scale values of the 3D object are not equal to 1 (in XYZ), the user must modify the scale and apply the transformation (*ctrl+a* -> *Scale*, or *ctrl+a* -> *All transforms*).



To set a regular grid, useful to segment a 3D object with the *Segmentation* tool, it is necessary to define the area of each tile of the grid compared with the dimension of the 3D object (to be segmented).
Before generating the *Cutter grid*, user can adjust the extent of each tile of the grid by changing the *Area value (m2)* on the right side of the *Set up cutter* panel.

After pressing the *Cutter set* button, if the dimension of the grid does not correctly fit the dimension of the 3D object, user can: select all the tiles of the grid (on the outliner of Blender, every tile of the grid is automatically named as *cutter* followed by a consecutive number *.001*, such as *cutter.001*) and scale them using the scale command of Blender (in this case, the reference point for the scaling action is automatically placed, by the add-on, on the lower left corner of the grid).
It is strongly recommended to use *Top Orthographic* view of Blender to set the position of the *Cutter grid*.

After clicking on the *Cutter set* button, a grid will appear in the viewport of Blender.
The grid will fully cover the entire XY-plane extension of the mesh that needs to be cut.
By default, the *Cutter grid* consists of square faces with 10-meter edges.