Yes, you can fly to that planet by pressing Enter,then type Planet Demo and press d to go to the planet.
Alternatively you can just load the procedural demo and start in front of the planet :
./main.py --main data/cosmonium-proc.yaml --default 'Planet Demo'
The zoom out effect is simply done using the change altitude Home or End and using the function “center camera on selected object” c when high enough to automatically rotate the camera
I would say out of the box no, the generated heightmap is distorted according to the spherical coordinates used (UV, normalization, …) but the displacement is done following the sphere normal. Unless bullet or ODE have a spherical heightmap mode it won’t work. One workaround would be to generate another heightmap which include the projection on the sphere and that would work, I think, with the physic engine as a plain heightmap.
It’s a known problem I’m using O’Neil atmospheric scattering and it has many limitations (one of them being the sky not blue enough when looking up, the atmosphere too saturated when the sun is in your back, …), in a future version I’ll switch to Bruneton scattering which is one of the best real-time atmospheric scattering. (To be honest, I spent so much time fine tuning the O’Neil scattering that I could have integrated Bruneton instead…)
The still visible stars is also a known problem I need to implement brightness culling to ignore object not luminous enough and also apply the atmospheric scattering on far objects when looking through the atmosphere. But for that I need first a physically realistic scattering.