Some viewing frustums are bounded by hither and yon planes.
The HOOPS 
Cameras — HOOPS Visualize HPS Documentation 2022.0.0 documentation (3DF Cameras — HOOPS Visualize 3DF Documentation 2022.0.0 documentation ) use “near limit” which is akin to hither and specifies the position of the view frustum near clipping plane. The near limit (nl) is a parametric value from 0 to 1 between the camera position (i.e. nl = 0.0) and the target (i.e. nl = 1.0).
The default near limit is -0.001. When the value is < 0, the near clipping plane will be automatically adjusted as close to the camera target as possible, with a minimum of an absolute value of the provided number. This approach generally makes efficient use of z-precision.
There are times when this automatic setting does not produce desired rendering results. For example, consider a scene containing geometry which is excluded from bounding. However, you would like to include it in the view. Assuming you know the size and position of the geometry excluded from bounding, you can calculate the near limit given the camera position and target such that the geometry excluded from bounding is not clipped by the near plane.
Further details:
SetNearLimit()HPS Cameras — Changing the Camera Near PlaneHC_Set_Camera_Near_Limit()HC_Set_Camera_Near_Limit — HOOPS Visualize 3DF Documentation