Hi,
Excellent structures to explore the marvels of Physics. Stuff for a tutorial video. Meanwhile some explanations. For starters : all the following models were made in WIP 7 (not 6) Bongo 3.0 WIP 7 - #4 by Luc
Model B 1138590816 B.3dm (609.7 KB)
Model B is really quite simple.
Both the rotor and the square ring are Physics enabled. The white sleeves are merely decorative, simply to make the image complete.
The rotor is connected to the World by a Spindle. This spindle is given angular velocity (a novelty since WIP 7 – the unit is radians/second). You can use the BongoConnectionsManager command to see the Connections.
The square ring is connected to the World by a Slider, and that’s it.
For both Physical objects the Object Parameters ‘Restitution‘ and ‘Friction’ are set to minimum.
The margin setting (an absolute requirement in Physics)is still in a highly experimental phase in WIP 7. The objects of the models used this post are built observing a interspace of at least 0.04 units (cm in this case). The default Physics Shape setting (Margin 0.04 + Offset enabled) in combination with my favorite setting in the Time manager of ‘Steps per second’= 300 and ‘Solver Iterations’=150, functions satisfactorily for this model.
Model A 1138590816 A.3dm (648.1 KB)
In Model A the rotor is rotated by Keyframes (just like in Bongo 2). This is a equivalent alternative to the use of ‘motor’ connections. The object is Physics enabled and marked “Kinematic” – what is necessary for it to meet its keyframe parameters.
The wheel is Spindle-connected to the shackle, which in its turn is Slider-connected to the World. The wheel is Gravity enabled. Both rotor and wheel are set; Restitution = minimum, Friction = maximum. The Physics Mash Quality is set to medium in order to have a smooth contact between the curvatures. Because the objects are built with consideration of (at least) 0.04 units (cm) interspace the ‘Offset shape’ can be disabled, hence avoiding intersection of the objects during motion. A smaller margin setting (0.02 units (cm)) even brings both wheels closer together.
Don’t try ZERO margin – Rhino crashes.
You may notice model A kind of ‘freezes’ during Precalculation. Don’t worry; Rhino will regain consciousness after a short while (about 30 seconds on my laptop). Apparently this is an enigma for the developers.
I have always found that the lack of surface-to-surface constraint was a shortcoming in Bongo’s 2.0 Inverse Kinematic, just like the elasticity of a spring. Physics offers both features and more. The price to pay is the multiplicity of parameters which play a role in Physics. Hopefully in the further we can bring some harmony and coherence in this as well as the highly necessary documentation.
A cute variation. 1138590816 C.3dm (595.1 KB)
Luc