We are working on a seastead design that will have a 40 by 16 foot living area above the water.
There will be 4 foot diameter legs/floats/columns that are about 24 feet long going out from 
from the 4 corners of living area and down into the water at 45 degrees, with half of
each column under water.   The legs/floats/columns will probably be made from 1/4 inch
thick duplex stainless steel on the sides and 1/2 inch thick on the dished ends.
They will have some modest pressure like 10 psi inside.

The bottoms of the floats will make a rectangle about 50 feet wide and 74 long.
From the bottom of each leg there will be 2 cables going to the adjacent corners.
The boyancy force is lifting up and the leg pushing against the platform leaves an outward
force that the 2 cables pulling in counter, so the leg ends up staying in place.
There will also be a cable making a rectangle between the bottoms of all the legs so we have some
redundancy in case one cable breaks.
The seastead is about 36,000 lbs I think but this is NOT a normal boat hull shape,
it is more like a tiny oil platform as far as drag.

We expect to use 4 low speed submersible mixers with 2.5 meter diameter propellers as 
thrusters, one on each leg/float.  There will be lots of solar and battery.
This should move at around 0.5 to 1 MPH plus any help from careful use of eddies and currents.






I would like to be able to have fairly simple set of 3D object and cables for seastead design ideas that I could simulate 
in waves as was done in this video:
   https://www.youtube.com/watch?v=PsPeasVy248

What open source software can simulate simple designs in waves as was done in that video?
That video is one of my designs.   The two legs in the front have a cable connecting the
bottoms so they make a triangle with a pivot point where it connects to the body, so they can move 
relative to the body.  Then from the bottom of each of the front legs there are cables
to the bottom of the back of the body.  The back legs are a mirror of the front. 
I want to be able to simulate this kind of movement and the direction of the thrust 
moves as the legs are rotated.   
I would like to be able to simulate in higher and higher waves and be able to tell
at what wave height some cable goes slack or the snap back tension is too high and it breaks (snap load,
or snatch load).  But I want to be able to visualize it so it is easy to understand
how things go wrong and what I might need to do different.

Another problem is that in a 24 foot leg we want to simulate from where 1/3 is in the water to
where it is almost all in the water, so some "linear assumptions" of some models probably don't
work.  And the legs can be at 45 degrees so that they have resistance to heave motion,
and also resistance of the legs to roll motion is important.  

I don't care about simulating propulsion for now.  It will go very slow and that is fine for
a seastead.  The important question at this point is how stable is a design on the 
waves and at what wave level might something fail.

I don't need perfect accuracy, this is sort of at the seastead brainstorming stage. 
But I would like some level of engineering simulation.  If we get something that 
seems to work we will build a scale model and eventually have a naval architect, so for now I want
something that is not too hard to use but gives useful engineering feedback on designs.

What about Project Chrono?   It seems this has all the pieces needed in one project 
including visualization and it is free?  But in searching youtube I don't find
boats or semi-submersibles in waves produced by Project Chrono.   Seems HydroChrono
and PyChrono could be good for me.

Capytaine and MoorDyn is another recommendation.  Both of these can be used from Python.
Claude Code and Cursor.ai can help me with Python scripts so it might go fast.

I was told that Blender can be used but that the physics simulations are not at all accurate.
Is that still true or has someone made something so I could do a reasonably accurate simulation
of a simple seastead model using blender?  And Claude Code or Cursor.ai could help me with this?

I was told maybe using WEC-Sim and MoorDyn could work.   Does this seem like a good way to go?
Would these let me make videos showing how a seastead design would work in the ocean?
Could WEC-Sim and MoorDyn handle this sort of thing?   It seems this needs MATLAB which
is not free (please estimate cost for a non-student in Anguilla).  Also seems this 
requites "Simulink" add-on and "Simscape Multibody" so there is a high total cost.
Really this should not be on my list of open source solutions. 

DualSPHysics is another one mentioned.  For this they recommend a system with a good GPU.
We have a Linux computer with a very good GPU.  How hard is this to use?

OpenFOAM is another one but it seems it is not recommended in the brainstorming stage where ease of use
is very important. 

Is there any other free software that might be a better way to simulate, test, and visualize my seastead design ideas?

I like Cursor.ai and Claude Code and may use them to help get simulations going.

Please compare the different options.  Try to estimate how long it would take to get a
simulating working in each.   Try to find a link to a youtube video of a simulation
in waves for each.  Estimate how accurate it would be for a seastead design with several solid cylinders
with pivot points and cables in waves.

I generally like Linux but we have Windows machines we can use if needed.