Hi everyone, I'm new to Houdini, so please bear with me .

I'm doing an animation where a vessel is handling some equipment offshore (harsh weather) using a crane.
I am trying to create a first rough simulation only to get the Vessel movement. I'm looking for that natural push of the waves, that would be impossible to accurately create manually.
In real life, the vessel will have a dynamic positioning system, that keeps it “locked” to a position based on realtime communication with satellites.
Of course, it will still be moving up, down (heave) and rotate all axis being pushed by the ocean, but it will not move front, back and sides.

How can I lock the position on X and Y, but keep it free to interact on Z, and rotation on all axis?

Thanks in advance for your time!

I am not an expert in this but I did a video a few days ago of a boat moving in water with its movement dictated by the waves automatically.

I used guided ocean sim so I will help you assuming you used that.



1) make sure your boat geo's hull isn't “hollow”. the hull should have a cover on it (like capping an open part of a geo when modelling) I had issues of my boat sinking when it was hollow.




2) go to the DOP network of the sim and delete the whole part that says Static Solver, Merge, etc and replace it with RBD object, go to bullet solver and play around with geo representation till you're satisfied with the output. next to bullet solver tab is the physical tab, play around there to change the “weight” of your ship and how it will interact with the waves.



4) in the same DOP network, dont forget to go to the flipsolver node, then to the solver tab and type in the feedback scale as 1, or else you will have no “floating” effect.

Best
Vish

Hi and thanks a lot for taking the time to add such detailed explanation.

I did exactly the same steps, the issue is that when simulating, the waves push my vessel away from the initial position.

So I'm struggling to find a way to keep the vessel in the same position (in the world space) during the simulation. Any idea how to do that?

Thanks a lot!

Hi!

Glad that it worked out for you, unfortunately I haven't come across the issue you mentioned. But I could try and help you solve it.
Is your FLIP sim tank animated/moving? If so, you will have to add a force to move the vessel in one direction, against the animation. Is the vessel deformed in any way? Have you tried changing the density, center of mass or rotational stiffness or any other option in the RBD Solver node?

Maybe this issue is beyond my limited experience, but there is no harm in trying to create the sim from scratch, hence removing your old setup. My sim worked after 8 trials

Let's go through the check list

Is your FLIP sim tank animated/moving? If so, you will have to add a force to move the vessel in one direction, against the animation. - I animated it to keep the vessel in the tank. However the vessel was still moving forward too fast, so at a point it was leaving the tank. Anyway, this method is not ok for me, since I will want to have a crane doing stuff, so the vessel must be in the same position at all times.

Is the vessel deformed in any way? Nope

Have you tried changing the density, center of mass or rotational stiffness or any other option in the RBD Solver node? - Yes, no good results.

I have also tried with some RBD Slider constraint. It seems to be working, but as far as I could understand how to set it up, it was keeping only one rotation. I need position on Y, and all rotation axis.

Thanks again!

Interesting, well unfortunately we have collectively reached the end of my experience with Houdini. Hopefully someone stumbles into this post and helps you. I am also waiting for the same magic to happen to a question of mine.

Best
Vish