I am trying to recreate the simulation from this YouTube video in Kangaroo2 under Rhino 6 for Mac and the Weaverbird plugin but am struggling to match the corresponding components and settings in Kangaroo2 with those from Kangaroo that were used in the original simulation.
Here’s something to get you started:
airbeam_example.gh (14.1 KB)
Many thanks! I’ll study closely.
Cheers -
Kevin
Units (mass & force) - Grasshopper (grasshopper3d.com)
@DanielPiker response:
Assuming your Rhino dimensions are in metres (m),
then your mass is in kilograms (kg),
and your force in newtons (N)
Then for your axial spring stiffness use EA/L
where E is Young’s modulus in pascals ¶
A is cross-sectional area in square metres (m2)
and L is the length of your spring in metres (m)
and timestep is in seconds (s)
a few things to bear in mind:
The speed at which your simulation runs at might not be 1 second per second, depending on the complexity of the simulation, the speed of your computer and the timer delay setting. Multiply the timestep by the iteration count to get the time which has elapsed in your simulation.
Using true values for E corresponding to stiff materials such as steel will often cause problems with simulation stability, unless you reduce the timestep and/or increase the mass of your particles (often necessarily by several orders of magnitude).
Remember that this inertial mass is separate from gravitational mass, and will not affect the final displacement of your system, only how long it takes to get there, so you can use a high fictitious mass to keep the simulation stable without changing things like the final displacement of your structure. This is a common technique in dynamic relaxation.
For loads due to gravity (in m/s 2), multiply the true mass of your particle by 9.81 (or thereabouts, depending on where exactly you are!) and apply it as a Unary force to the particle (for a linear element, just apply half its weight to the particle at each end).
How do you come up with the value of -0.1 for the strength of the Vertex Loads?
You’re using a strength of 100 on the Edge Lengths. According to your response in the old forum this would be EA/L but what is A for a membrane? Sorry I don’t get it just yet.
The strength input in vertex loads is a vertical vector in z-direction.
If you are working with SI units, that should be -0.1 Newton, afaik. I am also still investigating the accurate unit approach with Kangaroo, have only used qualitative values up until now.
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