Earliest version of SketchyPhysics, with simple joints that did not allow true runtime control. User interaction was limited to just pulling objects around the screen, and the physical size of the simulation was limited, although the physics were accurate.
The popular second release never actually left Beta phase; numerous bug fixes, massive world sizes and joint controllers were added, along with a selection of new joints and joystick support. Simulation-controlled camera was also supported, and a wide variety of games sprung up on the 3D warehouse.
Sketchyphysics 3 (RC1)
SP3, currently at release candidate one, added an almost unlimited world size. Magnet, thruster and emitter settings were added, along with a corresponding magnetic option, as well as the option to add an infinite bouyancy plane to the model. Joypad button and keyboard support has been added through joystick emulation, and ruby script support (With global variables) for control of the simulation has brought unlimited possibilities for real-time interactivity. A new, breakable fixed joint was also added, for connecting thrusters and emitters to parent objects, and for breakable environments/objects. A recording and exporting option was also added, for rendering the simulation.
More advanced scripting, with collision events and triggers, and limited sound effects have all been added in this experimental version. SP3 X is effectively a testing ground for ideas and control systems that may or may not be included, in some form, in SPIV. On touch (on collision) and on tick (on trigger) will be added to the UI for any physics body. On touch allows you to perform actions like playing a sound effect, or changing a global variable, whenever any collision between the selected object and another other part of the simulation occurs. The use of sound is limited due to SketchUp's play_sound command; only one sound can play at a time, and it can't be altered. This means that conventional physics sound effects, like a rock falling on the floor, won't work properly; true sound support may be added in SPIV. It should be noted that models made using this version will most likely not work with future versions, including SPIV.
This highly anticipated, totally re-written future version will make connecting objects and joints a breeze, with complex models that currently take hours to build sped up to mere minutes. A higher degree of interactivity and easier to use interface will allow modellers to easily create a physics environment, without the hassle of a joint connector tool, and with no problems copying and pasting joints..