View Units

The term 'View Units' refers to the 3D Unit space as seen from the camera's perspective, but before other perspective aspects - such as FOV - have been calculated.

Similar to 3D Unit space, the X component describes left (-X) and right (+X) directions; the Y component describes down (-Y) and up (+Y) directions; and the Z component describes forward (-Z) and backward (+Z) directions. But now, the camera is fixed to the center of the world and always looking down the -Z axis; all other points are now in relation to the camera.

In other words:

• X = (-infinity~+infinity, left~right in camera view)
• Y = (-infinity~+infinity, down~up in camera view)
• Z = (-infinity~+infinity, forward~backward in camera view)

For example, a point located at (0, 0, -10), with a camera located at (0, 0, -4), would be at (0, 0, -6) in view-space. Additionally, a point located at (0, 0, -10), with a camera located at (0, 0, 0) but a rotation of -90 degrees on the X axis, would be at (0, 10, 0).

Although the range is theoretically infinite, the large majority of that range will not end up being drawn due to being off screen. The X and Y axes range will be limited by the FOV and other perspective calculations, while the Z axis is always limited to a range of -1.f~-infinity with values > -1.f being behind the screen.

The view unit space is also where software clipping calculations are performed, such as near and far depth planes.

Despite not using a camera, the 2D Unit space uses the same Z values as the view unit space.