zSpace creates mixed reality systems that combine elements of virtual and augmented reality in a specially-built computer system, which has a quad-buffered stereo display that works with IR-tracked active-shuttered glasses and a stylus.
xeogl is an open-source WebGL-based 3D engine created at xeolabs.
zSpace shipped xeolabs one of their zSpace 300 displays so that we could develop xeogl demos for its beta WebVR support. If you were at GDC 2017, you might have seen those demos running at the Khronos booth.