The Model Viewer 3D view window can be moved, resized, minimized, and maximized. When the 3D view window is selected, the images and models can be selected, viewed, and controlled via keyboard commands and mouse movements. For a frame of reference, the 3D view window has a background colour (the default is light blue), and shows the Local Space Rectangular U, V, and W axes as lines. The axis lines meet at the origin (0, 0, 0).

The Model Viewer always faces the origin and cannot turn away from it, but as described later in this section, the current item being viewed can be rotated as desired, and the virtual camera can be zoomed in or out. Models being displayed use the origin indicated by the axis lines as their local origin. If the geometry of a <Model> is not located near the origin of its SRF (and thus, not near the Model Viewer's origin), it may be out of the field of view and only visible by zooming out. By default, the Model Viewer assumes that each root <Model> is constructed close to the origin and is relatively small, leaving it to the user to adjust the zoom and other viewing controls as desired if this is not the case.

The background colour can be modified, as shown in the following table.

The orientation of the model / image can be controlled for ease of viewing, as shown in the following table.

The distance of the virtual "camera" from the model / image can be controlled for ease of viewing, as shown in the following table.

The display mode of the geometry in a model can be controlled by the user, as shown in the following table. The display mode can be set to fill, wireframe, or outline mode.

Fill mode displays geometry with colours and / or textures, that is, filled in.

Wireframe mode displays only the edges of geometry, outlined in the colour of the geometry. For example, for a <Polygon> instance, the boundary lines connecting the vertices would be shown, but the interior of the <Polygon> instance would not be shown.

Outline mode displays the geometry with colours and textures filled in, outlined in black.

The rendering of blended textured geometry can be toggled, as shown in the following table.

The geometry of models can be shown with or without texture mapping turned on. If texture mapping is turned off, only the colour information, if any, of the geometry is used for rendering.

Depending on the hardware and underlying OpenGL implementation available, the user may wish to enable or disable the internal use of OpenGL display lists by Model Viewer. The usage of such lists will be noticeable only under some conditions, depending on whether textures are displayed and whether parts of the model being displayed are moving.

This option is provided in case it will allow the user to speed up rendering on a particular platform.

The user can toggle between viewing the textures from the <Image Library> instance of the input transmittal, if one is present, and the models from the <Model Library> instance. By default, the textures are displayed in sequence as they are initially loaded by the application, which then automatically puts itself into model viewing mode after all the models are loaded.

If the user invoked Model Viewer initially by turning off either textures or models, then the toggle command will have no effect.

The user can control the quality of texture rendering, as shown in the next table, allowing the user to trade rendering quality for rendering speed.

The user can step through the images (if the application is in image display mode) or models (if the application is in model display mode), as shown in the following table. (The toggle command for switching between modes is covered earlier in this section.)

Note that this does not display every model in the given <Model Library> instance, but only the models that can be instanced as free-standing objects; that is, the models which have a model_reference_type of either SE_MODREFTYP_ROOT or SE_MODREFTYP_ROOT_AND_COMPONENT.

The light source and its characteristics can be controlled as shown in the following table.

When in model viewing mode, Model Viewer can print out the data structure of the current model and current viewing parameters, as shown in the following table.

To exit the Model Viewer application, press the <escape> key.

The bounding volume view for models and their individual components can be toggle, as shown in the following table.

The back face culling can be toggled, as shown in the following table.

Models with articulated parts can be animated, and the animation can be controlled by the user, as shown in the following table.

Models containing <State Related Geometry> can be controlled by the user, as shown in the following table.

Models containing <LOD Related Geometry> instances can be controlled by the user, as shown in the following table.