Navier-Stokes fluid simulation explained with Godot game engine (myzopotamia.dev)
153 points by myzek 4 days ago
nlawalker 6 hours ago
If you haven't tried Animal Well, give it a shot. The whole game and its custom engine are like 35MB and it's filled with really cool visuals and physics powered by fluid equations.
myzek 4 days ago
So once upon a time I stumbled upon simulating fluids in gamedev and I really wanted to learn how it works. Fast forward 2 months and I decided to write down everything I learned to hopefully make it easier for others in the future!
magicalhippo 4 days ago
Fluid sims are just so darn fun! Nice writeup, very accessible.
Couple of notes, I think you forgot to apply timestep when adding rocket exhaust velocity, pretty sure it should be
u[idx] += backward.x * flame_velocity_amount * falloff * delta
v[idx] += backward.y * flame_velocity_amount * falloff * delta
myzek 4 days ago
Yeah it seems I missed that, adding the rocket at the end was a cherry on the top and I was so exhausted already I'm surprised it even works lol
magicalhippo 3 days ago
brandonpelfrey 6 hours ago
Great job. I have spent a lot of time working on fluid simulations (I still am). Glad to see more people still mesmerized. If you’re interested, this rabbit hole goes very deep.
nick__m 7 hours ago
excellent article, great vulgarisation and human written !
Thank you
genxy 6 hours ago
The unlinked Jos Stam paper is available from his website https://www.dgp.toronto.edu/public_user/stam/reality/Researc...
Stevvo 6 hours ago
For anyone wanting to dive further, Fluid Simulation for Computer Graphics by Robert Bridson is the definitive textbook.
markstock 4 hours ago
Before you go adding vorticity confinement, consider performing a higher-order backward advection scheme (Runge-Kutta 2nd or similar), and using a higher-order interpolation method (triangle-shaped cloud instead of bilinear).
In my implementations I use 4th order for both and vortices stick around a lot longer.
amarant 5 hours ago
This is great! When I have some leftover time I want to try copying this implementation for 3D. I reckon I could get away with minimal modifications to support the third axis...I think...
That'll perform even worse though, hopefully my CPU can handle it or I'm gonna need a lot of leftover time to make a shader
markstock 4 hours ago
You are correct: Stable Fluids extends to 3d relatively easily.
jedimastert 3 hours ago
I appreciate the AI disclosure, I hope that becomes normalized
frankdlc222 4 days ago
This is really cool. I love how much detail you went into explaining the setup and walking through each piece of the simulation. Definitely bookmarking this to play around with later!
amelius 6 hours ago
Did they test if it satisfies the relevant conservation laws?
brandonpelfrey 6 hours ago
It won’t satisfy those laws. It’s also not a goal though of this post.
amelius 5 hours ago
I mean if you're writing a ray tracer and the reflected light has more intensity than the light sources, then that's not desired. You can have the same sort of thing going on with a fluid simulation.
dahart an hour ago
markstock 5 hours ago
analog8374 7 hours ago
Oh don't let us pinch zoom. That would be a disaster.
zamadatix 6 hours ago
Assuming you mean the site - pinch zoom & pan works for me on Windows and iOS?
analog8374 6 hours ago
well android chrome doesn't