Mari 4.5v2 docs:

Canvas toolbar

The Canvas Toolbar lets you set the view options for the UV and 3D views.

Canvas Toolbar Controls

Control	Type	What it does	Notes
	button	Toggle whether to show the wireframes on the model.	You can also press Shift+W to do this.
	button	Toggle between showing the patches in the UV view: • as they appear as part of the model, and • as they appear when exported (that is, as square images, with over-paint areas around the corners of the patches).
	button	Toggle whether paint can be projected onto UV patches located outside the shells of the original geometry.	This control is only available in UV view.
	button	Switch to the orthographic camera view.
	button	Switch to the perspective camera view.	In this view, you can set the near and far clipping planes and the field of view.
	button	Switch to the UV camera view (the UV tab). This gives you a “flat” view of the patches in the model.
Near	entry box	Set the value for the near clipping plane. Mari doesn’t display parts of the scene that are closer than the Near plane.	This control is only available in the perspective camera view.
Far	entry box	Set the value for the far clipping plane. Mari doesn’t display parts of the scene that are further than the Far plane.	This control is only available in the perspective camera view.
FoV	entry box, slider	Set the value for the field of vision. This controls how much Mari distorts the view when applying perspective. At 0, the perspective camera gives exactly the same view as the ortho camera. As the value increases, the distortion increases.	This control is only available in the perspective camera view.