Pix4Dmapper does not offer stereo-viewing options.
It offers the rayCloud. The rayCloud is a tool that can replace the stereo-viewing functionality. This is because the rayCloud combines the 2D input images and the 3D output pointcloud in real time.
In case that stereo-viewing is necessary, Pix4Dmapper exports very accurate camera parameters (internal and external) and undistorted images that can be used by other traditional photogrammetric software such as Inpho. For more information about how to import Pix4Dmapper outputs into Inpho: 202559629