Viewports and Clipping

Conceptually, a viewport is a two-dimensional (2-D) rectangle into which a three-dimensional (3-D) scene is projected. In Microsoft?Direct3D? the rectangle exists as coordinates within a Direct3D surface that the system uses as a rendering target. The projection transformation converts vertices into the coordinate system used for the viewport.

You use a viewport in Direct3D to specify the following features in your application.

• The screen-space viewport to which the rendering will be confined.
• The range of depth values on a render-target surface into which a scene will be rendered (usually 0.0 to 1.0).

This section discusses clipping, the last stage of the geometry pipeline. The discussion is organized into the following topics.

• Viewport Rectangle
• The Viewing Frustum
• Clipping Volumes
• Viewport Scaling
• Using Viewports

Direct3D implements clipping by way of a set of viewport parameters set in the device.