### Introduction

The 3D viewer uses a set of stock VTK display elements to allow the user to view, and manipulate, the selected images. There is a main display showing each volume according to their designated display intent (modifiable via the Image Type control of the Layer Information Dialog) as follows:

Unknown | Not displayed
Main image | Displayed as a surface with optional cut-aways to reveal the image data and any other images within.
Mask/Label | The image is displayed as a surface with the label value at each appropriate vertex which will appear to be a group of surfaces, one per label, coloured according to the label value for the given region.
Statistic | The statistical data is blended into the main image so that it appears on the surface of the cut-away planes.
Diffusion tensor | Not displayed