Fancy is a physics computing project developed with fanciful ideas of creating a programmatic sense of fantasy for the virtual minds of the coming AI revolution. 🎭
To this end a general purpose physics engine is under developement and is tested on some basic examples in a Web Demo.
The physics engine currently involves:
- Up to 64 thousand objects
- Interactions include:
- Point & cloud gravitational and quasi-electrostatic accelerations
- Drag & pressure effects between close neighbour objects (involving precise collision detection).
- Model accuracy and stability is maximised with a refined adjustment of velocity data to fit integration timestamp related to the basic 'verlet integration' velocity adjusment.
- An efficient R-tree class spatial index is created and maintained for optimising most object interactions.
The workbench involves:
- Basic UI with readings and controls
- Model entities rendered as rescaled particle cloud, or simple shaded spheres.
- Wireframe view of the spatial index.
- raytrace selection of objects by mouseclick
- Adjustable rendering frame interlace rate
The demo selects and initialises virtual worlds called 'figments' and renders them for display and testing. Everything is currently orbital in kind, as this is a most straightforward model to begin with. The demo has keyboard controls for zooming and time controls and some readings about the focused object. Objects can be mouseclicked accurately to zoom on them.
Engine performance is exercised with precise information which NASA provides for all solar system bodies via. its 'JPL email service'. A quick test which compared the simulated position of the Earth after a year of 'fancy' time, with Nasa JPL's year-on information, found the two positions to be within about 70,000 km of each other - this is quite close considering the circumference of Earths orbit is about 15000 times as long: 1,000,000,000 km. By reducing the constant G by 0.0035 % from 6.67408e-8 to 6.67384789e-8, the difference between the discrepancy can be reduced to as low as 10 km.
This solar system test is less than perfect yet: Saturns moons go awry after a few months for some reason, their data may be corrupted or there may be an engine bug triggered by them. Also the planet rendering can be confusing as it can boost object size wrongly. And object clicking doesnt work well.
It is possible javascripts 64bit float numbers can hinder the accuracy of astrological scale models. NASAs figures for position and velocity are given as 80bit floats, most of the solar system has potentially millimeter accuracy at 64bit float but special care and formula arrangements could be required to realise that potential. Full accuracy solar system simulation is beyond Fancy's immediate goals.
This figment is proceeduraly generated to have an appearance like the visualisations of near earth asteroids and objects which have been publicised. Quite precise data for thousands of NEOs is available, but its needs converted to position and movement vectors to use in this simulation.
This system is plotted according to the planets publicised mass and orbits. The closeness of the orbits in this system seems very exceptional.
These figments currently test the 'Spotmap' - which is a spacemapping data structure used to recursively associate objects in relation to separation distance. A view of the spotmap is toggled with the 's'. The spotmap is used in these examples to accelerate gravitation calculations between 250 massive bodies in 'MassRing' and 1300 in '4MassRing'. It will be more useful to optimise collision detection/scheduling and to apply close proximity effects such as liquid bonding, between objects.
The 'spotmap' is used in this figment to apply a basic pressure and drag function between close neighbouring objects. The functions are calibrated along with gravity, producing some curious looking quasi-astronomical phenomena.
- The Cursor keys spin the viewpoint around the focal point
- A,Z moves toward,away from the focal point
- Crtl + Cursors moves the focal point
- Keys:
<, >.change object in focus - Click on object sets it as focal point
- Click empty space sets focal point on current z-axis level
- C start/stops simulation
- S shows bounds of space index (spotmap)
- g turns off gravity
- x pulsates world
The Fancy Wiki has some design docs.