### 3D properties dialog

The dialog has two sections: "Basic" - dealing with lighting and surface colouring; and "Advanced" which allows the user to tune some of the parameters used to determine the shape of the extracted surface mesh. Usually the surface in question is being determined from a segmented brain and is intended to approximate the "pial" surface.

#### The basic settings

Interpolation Changes how the shading of vertices is calculated. Possible options are: Flat, Gouraud and Phong. In most cases Gouraud is the most appropriate setting. Ambient Determines the percieved intensity of the main light source. Diffuse This controls how much of the ambient light is scattered back to the observer and other objects in the scene. Larger values add substance in the form of shadows and detail. Opacity Controls how opaque the surface will be rendered. You can also modify opacity via the slider on the layer list panel. Specular The intensity of the light reflected from the surface of a shiny object. Specular power How shiny the object is. Increasing this value will give the object smaller highlights as they become less diffuse. Surface Colour These controls allow you to change the colour of the surface representing the main image. |

#### Advanced settings

These settings determine how the pial surface is rendered. Modifying these values allow you to customize the look of the main images surface representation.

| Gaussian: SD Sets the standard deviation of the smoothing kernel applied to the main surface. Gaussian: radius Sets the radius of the smoothing kernel applied to the main surface. Marching Cubes: threshold The upper threshold of the marching cubes algorithm. Higher values generate deeper sulci. SmoothPolyDataFilter: iterations For each vertex v, the coordinates of v are modified according to an average of the connected vertices. The number of iterations determines the smoothness, i.e., the higher the number the smoother the resultant surface. SmoothPolyDataFilter: relaxation factor Controls the amount of displacement possible during each iteration of the algorithm. PolyDataNormals: feature angle Used to control the angle at which the algorithm defines an edge as "sharp". When sharp edges are present, the edges are split and new points generated to prevent blurry edges (due to Gouraud shading).