# Basics

Polygonal has a minimal user interface consisting of a Viewer and a Menubar.

- The Viewer is the central widget for manipulating meshes.
- The Menubar provides access to all commands.

## Opening a Mesh

In order to load a new mesh use the {menuselection}`File --> Open` menu entry and select the file you wish to open. Alternatively, use the {kbd}`Ctrl+O` keyboard shortcut. Polygonal supports reading meshes in the following file formats:

- STL (.stl)
- Wavefront (.obj)
- Geomview (.off)

```{important}
The input has to be a 2-manifold surface mesh. Polygonal does not support non-manifold meshes.
```

You can also open a file by drag and drop. Simply drag the mesh file you want into the application window and it will open automatically.

## Using the Viewer

The Viewer is the central UI element for manipulating and inspecting a mesh. It provides a trackball interface for rotating, panning, and zooming in to the mesh. Press down one of the following mouse buttons and move the mouse perform the desired action:

- *left mouse button*: Rotate the mesh around its center
- *wheel button*: Pan the mesh in $x$ and $y$ direction
- *right mouse button*: Zoom in/out

Alternatively, you can use the {kbd}`Alt` and {kbd}`Shift` modifiers to move and zoom:

- Hold down {kbd}`Alt` and press the *left mouse button* to move
- Hold down {kbd}`Shift` and press the *left mouse button* to zoom

Reset the view to the default view by using the {menuselection}`View --> Reset View` menu item.

## Saving Files

You can save the current file by using the {menuselection}`File --> Save` menu item or by using the {kbd}`Ctrl+S` keyboard shortcut.

```{important}
This will only save the current mesh to the internal browser file system. Use the {menuselection}`File --> Export` menu to download the mesh to your local file system.
```

## Exporting Files

You can export the mesh by using one of the {menuselection}`File --> Exoprt` menu:

- {menuselection}`STL (.stl)`
- {menuselection}`Wavefront (.obj)`
- {menuselection}`Geomview (.off)`

## Closing Files

Close the current mesh using the {menuselection}`File --> Close` menu item or the {kbd}`Ctrl+W` keyboard shortcut. All unsaved changes will be lost.

## Reverting Changes

Revert the current mesh to the last saved version using the {menuselection}`File --> Revert`  menu item or the {kbd}`Ctrl+R` shortcut.