Cam
From GMod Wiki
This directs all drawing to be done to a certain 2D or 3D plane or position, until the corresponding "End" function is called.
The matrix functions exist, but are mostly unusable unless you're familiar with the source engine's layout for each aspect.
cam (Library)
cam.ApplyShake
cam.End2D
cam.End3D2D
cam.End3D
cam.EndCameraPos
cam.EndOrthoView
cam.IgnoreZ
cam.PopModelMatrix
cam.PushModelMatrix
cam.Start2D
cam.Start3D2D
cam.Start3D
cam.StartCameraPos
cam.StartMaterialOverride
cam.StartOrthoView