Viewport class

A IRenderTarget contains at least one viewport for rendering the scene.

The Viewport type exposes the following members:

Property	Description
frustum	Gets or sets the camera of this `Viewport`
enabled	Enable or disable this viewport.
render_target	Gets the render target that created this viewport.
area	Gets or sets the area of the viewport in render target.
z_order	Gets or sets the Z-order of the viewport.
background_color	Gets or sets the background color of the viewport.
depth_clear	Gets or sets the depth value used when clear the viewport with depth buffer bit set.