Thanks for the reply. I set graphics memory to 1,024MB. Nevertheless, when I start the game it shows the following dialog:
You have obsolete openGL version (2.1).
Update your graphics card driver or install compatible hardware.
On the game page (en.spaceengine.org) under requirements it says,
Video: 1 GB, Nvidia or AMD/ATI
OpenGL 3.3
In the control panel, the properties of the monitor says "Hardware: on Parallels Display Adapter (WDDM)" From that I infer that the fact of the actual hardware (AMD Radeon) is not reflected into the VM.