What is Demeter?

An application designed for scientific terrain (DEM/DTM) visualization from a simulator aspect. You can discover the real shape (and atmosphere) of our planets and moons and visit places where no one has been before. All this at the time of your choice including time lapsing.

How to run

1. You need an installed copy of Celestia. You can download it from here.
2. Extract the content of the executable package below (there's no installer)
3. Optional - copy the desired celestial data packages into the data/celestia folder (only copy, no need to extract)
4. Optional - copy mars2020_sensors.zip archive into the data/ folder if you want to enable "real" cameras (only copy, no need to extract)
5. Optional - copy issi.zip archive into the data/ folder if you want to explore the Interior of the Internal Space Station (only copy, no need to extract)
6. Run DEMETER.exe

System requirements, prerequisites

• Vulkan 1.0 capable GPU with at least 1 GB VRAM
• An installed copy of Celestia. The application tries to detect its installation directory.

Notes

• The package is tested on GeForce 1650M and Intel UHD.
• All screen shots and video are captured on that GeForce at real time

Visualization

Global DEM visualization

Several global elevation maps are available about the celestial bodies of our solar system. Since these maps consume a significant storage (even in compressed format) those are accessible as separate data packages..

Demeter enables the followings to examine:

Celestial body	Data package URL
Sol/Mercury	mercury_mod.zip
Sol/Venus	enus_mod.zip
Sol/Earth	earth_mod.zip
Sol/Earth/Moon	earthmoon_mod.zip
Sol/Mars	mars_mod.zip
Sol/Mars/Phobos	marsphobos_mod.zip
Sol/Ceres	ceres_and_vesta_mod.zip
Sol/Vesta	ceres_and_vesta_mod.zip
Sol/Jupiter/Ganymedes	ganymedes_mod.zip
Sol/Jupiter/Io	io_mod.zip
Sol/Saturn/Enceladus	titan_and_enceladus_mod.zip
Sol/Saturn/Titan	titan_and_enceladus_mod.zip
Sol/Pluto	pluto_and_charon_mod.zip
Sol/Pluto/Charon	pluto_and_charon_mod.zip
Sol/Bennu	extras.zip

In addition some spacecrafts are also available

Spacecraft name	Description	Data package URL
Messenger	Flyby at Mercury, 2007	extras.zip
Messenger	Flyby at Mercury, 2008	extras.zip
Magellan	Orbit around Venus	extras.zip
VEX (Venus Express)	Orbit around Venus	extras.zip
ISS (International Space Station)	Orbit around Earth	extras.zip
LRO (Lunar Reconnaissance Orbiter)	Orbit around Moon	extras.zip
Dawn	Flyby at Ceres, 2011	extras.zip
Dawn	Flyby at Vesta, 2015	extras.zip
MRO (Mars Reconnaissance Orbiter)	Orbit around Mars	extras.zip
MEX (Mars Express)	Orbit around Mars	extras.zip
Cassini-Huygens	Landing of Huygens on Titan, 2005	extras.zip
New Horizons	Flyby at Pluto and Charon, 2015	extras.zip

Local DEM visualization

You can explore alien terrains from a close up point of view of an astronaut or a free fly camera. You can download those from various sources; currently IMG and GeoTIFF files (in raster formats) are supported. If it's necessary, the application automatically tries to scale down the terrain to fit into the memory. The terrain is visualized after a stereographic projection.   

Here are some useful links: 

Celestial body	URL
Sol/Earth	OpenDEM
Sol/Earth/Moon	Index of /data/LRO-L-LROC-5-RDR-V1.0/LROLRC_2001/DATA/SDP/NAC_DTM (asu.edu)
Sol/Mars	HiRISE | Digital Terrain Models (uahirise.org)
Sol/Mars	MEX HRSC (wustl.edu)
Sol/Jupiter/Europa	Europa DEMs and Orthoimages in Support of Bland et al. 2021 (Remote Sensing) (figshare.com)
Sol/Jupiter/Io	Io Galileo SSI Tvashtar Paterae DEM and Orthoimages 900m v1 | USGS Astrogeology Science Center
Sol/Saturn/Titan	Index of /psa/ftp/Guest-Storage-Facility/IPGP_Titan_Huygens_V1.0 (esa.int)

After you found and downloaded the terrain data, you can easily load it into Demeter. You might want to check the compatibility before. When the terrain is loaded, the whole scene is teleported to the center of it (and possibly to a new planet or moon).

Simulation

Astronomy simulation

Celestia 1.6.1 is responsible for this. This also means you can freely play with time. You can read more about this complex simulator here 

Drone (helicopter) simulation

You can control Ingenuity aka the Mars Helicopter while the wind also affects its flight. 

Quad bike (vehicle) simulation

This simulation uses the built-in vehicle simulation of the Bullet physics engine. You can feel how the gravity affects the driving experience.

IFOPE (cloth) simulation

The International Flag of Planet Earth is a part of the scene if you enable it in the main menu. This is also a built-in feature of the Bullet physics. The wind affects this, too.

Lighting and acoustic simulation -Interior of ISS

A huge part of ISS is discoverable with zero-gravity experience in first person view. The scene is illuminated with photometric direct and indirect lighting (even Earth illuminates the interior). There are crew lock bags to play with and ColorChecker boxes can be spawned to play with.  You can also find Neil Armstrong Spacesuit. Sounds are fictional but may resemble the original ones. Acoustic simulation is also included in this scene: frequency based sound obstruction, Doppler effect, HRTF for binaural 3D surround sounds.

Physically based lighting

Every computation obeys (more likely approximates) the laws of photometry and are performed in 32 bit floats. The main light source is always the nearest star, the calculation starts with its black body spectrum then the rendering equation is applied where the diffuse BRDF is the Lambertian and the specular BRDF is the Cook-Torrance model or Blinn-Phong. The implementation is based on Google Filament. 
In a scattering medium like atmosphere or cloud, one of these phase functions is used: Rayleigh, Cornette-Shanks or a look up table. The scattering and extinction coefficients are calculated from the material composition of the medium.

Physically based camera model

The well-known parameters such f-stop, shutter speed and sensitivity defines the exposure characteristics of a camera in Demeter. The implementation is based on Google Filament. The result of the depth of field is approximated (with the calculated focal length) as well as the motion blur. 

Camera lens distortion and image color transfer

By the default, the Carpentier distortion method is used but you can meet real cameras (meaning the distortion is calculated from an intrinsic calibration). These cameras are:

Name	Long name	xxx	Distortion model
HELI_RTE	Return to Earth camera	Ingenuity	CAHVORE
HELI_NAV	Navigation camera	Ingenuity	CAHVORE
NAVCAM_LEFT	Left navigation camera	Perseverance	CAHVORE
NAVCAM_RIGHT	Right navigation camera	Perseverance	CAHVORE
MCZ_LEFT	Left Mastcam-Z	Perseverance	CAHVOR
MCZ_RIGHT	Right Mastcam-Z	Perseverance	CAHVOR
SUPERCAM	SuperCam (Remote Micro-Imager)	Perseverance	CAHV
PIXL_MCC	PIXL (Micro-Context Camera)	Perseverance	CAHVOR
SHERLOC_WATSON	SHERLOC (WATSON)	Perseverance	CAHVOR

Image color transfer method is utilized in order to enhance realism of these cameras.

Other features

• Free fly camera: during exploration, this camera is free to move anywhere even under the ground.
• Magic carpet camera:  during exploration, this camera is always hovering above the terrain at a constant height.
• Astronaut: during exploration, you can navigate (walk or run) or look around with an astronaut
• Telescope: you can lock the free camera at a certain celestial object
• You can see the asterisms from any point in the solar system at any time.
  
• You can make traditional screenshots but can also take HDR or HDR sphere pictures. 
• Celestial exploration - you can visit any celestial object by entering its name.