Get a free 30 day trial and 20% off an annual plan at brilliant.org/acerola ! #ad Simple topic today thanks friends happy new year

I'm actually really glad the cat gag hasn't been removed because I find it genuinely fun to watch your cat

My favorite fake bouyancy is in the original half life. All they did was put a trigger plane slightly under the surface of the water, every time an object touches the plane it just kinda punches the object up a little bit And that's all it does

"Did Archimedes ever take another bath?" Actually yes, IIRC there were historical records uncovered in 2011 stating that he once bathed in blood inside Heavy's ventral cavity

NO BATHS, NO MATHS

I have one question - is there any correlation between buoyancy of the objects and successfulness of their distant relationships? Having trouble with my drowning simulation

The funny PNG computing man is back! My day has improved drastically

Great video! I had to create a relatively convincing buoyancy sim at work for VR interactable objects. You did a fantastic job with this break down! The difficulty I found, most of all, was creating an interface for designers to end up implementing the parameters, per object, to determine physical values. Lots of fun! Designers have such high standards but then want simple controls!

Working on a buoyancy sim for my own ocean.. watching you go through the same thought processes as me was funny. To address the issues with the voxel approach (no control/ bad performance) i did a couple things instead of a plane fitting algorithm - Based the rotation of the object, if it aligned orthogonally with the oceans suface such that the cubes could same from ones "below" them, i could drastically cut down on the # of samples especially for ships which almost always maintain a similar equilibrium -To address control, i worked the buoyancy equation backwards to calculate the water density based on a desired height for the object to be at equilibrium for. This meant that for ships, all I had to do was set a specific y value to be the waterline and the program made it float there no matter what. It also meant the water density was different for each object, but that didn't have any effect so long as there weren't things that were Massively overweight and floating I have some questions about the gpu read back: What if you calculated, on the gpu, the lower frequency waves slightly ahead in the future such that when the packets arrived, they would be right on time instead of lagging behind (this would also help with noise). I'm not sure if its practical but I just thought of it now

Uh, thinking about the pressure on the surface of the object is actually way more applicable to how 3D objects in game engines are usually implemented. This can be done by using a displacement mesh, cutting it at the water surface and then calculating the pressure and area for each triangle to get the forces. Implementing things like slamming forces and surface friction also becomes possible. There is a great article by Jacques Kerner about the Just Cause 3 boat physics on the gamedeveloper website and a person called Habrador also has a Unity implementation with sample code based on it.

One thing that could also work is having the gpu return a grid of water normals around the origin of the buoy to the cpu where you calculate the difference in normals over time and apply that to the buoy. That way the cpu is interpolating the data in order to calculate while waiting on the gpu, so the buoys are always animating.

I kept thinking, wouldn't it be better to ask for the data in bulk? The time to make lots of little requests scales way faster than making few big requests. This is due to the individual overhead attached to each request. (Now imagine instead of talking to the GPU, you're sending data over the internet. Had to tackle that in my job.) Probably just shoving the heightmap into a render texture and reading that.

Your thumbnail made me realize where the word buoy comes from, so thanks for that random little insight :) (seems kinda obvious in hindsight, but then again I suppose most things do)

Since you mentioned the signal domain, the "noise" can be filtered with a simple damping filter (also known as Exponential Moving Average Infinite Impulse Response filter): o = lerp(i, o, t). This effectively removes high frequencies from your signal, simulating inertia and mass. Of course, you don't have to stop to just one filter (1st order), you can have up to 3 filters chained one after another for an even smoother frequency cutoff.

Amazing video. Love your content.

My first idea would be to sample the 4 corners, use a plane approximation, and filter that using a moving average window.

i remember doing this myself and following a bunch of tutorials and what we ended up doing is getting the bounding box and then at the 4 corners of the intersecting plane with the water use spring physics to pull the current “plane” into alignment. i by no means came up with his myself but it’s a neat solution that gave really nice results, especially since we had a full copy of the water shader living on the cpu and could then use this copy to interact with the rest of the cpu things

Isn't it possible to just stream a downscaled height texture of the water back to the CPU? That should be much faster than individual reads for each object. Also you can set a spring constraint in many physics engines, even the one unity uses. If you add an X/Z (or X/Y) lock to the body, you end up with a buoy that doesn't move and doesn't topple over (artist control) while still being physics based.

One thing I think could quite improve the simulation is drag. Objects in water experience significant drag which slows them down (tried running through a pool? Impossible). Moving objects, like ships, rely on there being far more drag sideways than forward/back in order to be able to turn properly. I made a game in 3rd year in high school where I implemented water simulation. The boats I used would sink noticably when jumping into the water, and would slide across when turned. Adding drag (high drag sideways, very high vertically) mostly fixed the issue. I don't remember much from his previous water sim video, but if the simulation isn't incredibly compute heavy, you can in fact just simulate it on the CPU for every point you need. I sampled 7 points on a boat's hull in order to determine the buoyancy.

Fantastic video as always! We need more of what you have to offer! Your work researching, explaining, and covering topics without just talking about what your code does and showing code allows us to learn to code it on our own in our own ways. Keep this up! I'll for sure be subscribing to your Patreon!

I think you might be able to optimize considerably the voxel technique by using different shapes. With that buoy example, 4 or 5 well positioned voxels might be sufficient to do both the height and the tilt, with one in the center and the rest in corners...

Great video. Presenting vastly different solutions is very important, if you need to decide which solution fits your project the best with a limited time budget. Thank you for providing this to everybody, Acerola. The voxel solution looked very promissing here. It could be something that might become feasible in future games. Almost then years ago I worked on a game with a large body of water and wrote a full height field sim on the GPU and a per-sample sim on the CPU. They were deterministic and ran synchronised and used artist-controlled wave patterns to improve control over visuals and gameplay. It was similar to sum of sinuses, it makes several things simpler, but less realistic, as was pointed out in this and an earlier video. You could perform multiple thousands of CPU side "samples" (they were pattern samples and computations instead of actual samples of a map, the height field did not exist as such on the CPU side) within a reasonable budget (a single / few ms out of 33 / 16 ms per frame) on then-current consoles (with very weak tablet-level CPUs), of which we only used a small fraction in the final game (probably low hundreds, it never came up in the profiler, so I don't know). To reduce the CPU side overhead, you could bundle multiple samples that were then computed in one go. That yielded some meaningful savings for scenarios like the one in the video. The approach in that game was otherwise quite similar to the last solution. I was a little worried for a while, that I had missed an obvious better solution. 😅 Seriously, there is always something new to learn in these videos, even if you've already got some experience in the topic. PS: This is one of a few select channels where I don't mind the in-video ads. I usually don't skip them anyway, but with these channels, I genuinely enjoy the presentation, as weird as that might be.

I like the part in the intro where it's just a color background with texts, reminds me of monogatari series, so nostalgic ahhh😊

Yo Ace I’m loving binging your whole channel as I learn blender

Love that you named your cat Brilliant, and that they sponsored this video 💕

My immediate thought in regards to the lag is that since it, gameplay-wise, doesn't matter what time the ocean simulation is at, if you could hold back the clock for the rendering time, you could have the wave visual sync up with the values you got from the gpu->cpu reads. I'm too lazy to go back to the previous vid to chek how the sim was stored, but given it's not just a simple function of time like a sum of sines would be, I suppose this might require a circular history buffer of wave maps or something

I'd love to see you take on some rudimentary water interaction physics pretty similar to how RDR2 detailed theirs in the GDC paper. I think that would be an extremely interesting thing to add to your ocean simulation. Plus it'll help as you add more objects to the world

Acerola must’ve tried a long distance relationship that went bad. Cause that was very accurate

I don’t know what it is about the way you make videos but don’t stop, your videos feel so casual while still being informative and it’s great.

16:00 so my suggestion is to use a first order lowpass filter here (there's some similarity between ideal springs and lowpass filters), each frame setting the value to partway between the last value and the updated value. any changes too far above the filter's cutoff will be reduced and that smooths it out. it can completely remove changes if they happen too fast, so sometimes it requires scaling up the input or output to compensate, but a higher order filter could more easily allow changes you want while still smoothing it out. a higher order filter could have a higher Q and rock back and forth faster when the frequency is just right, as often happens. there's possibly some overlap between this and what you were doing but hopefully it gives you some ideas to explore.

an acerola video a month keeps one feeling comf

My favorite math daddy

You say bad game design, but I think it's perfect. I want large waters to be anti-player boarders in my dream game. Having rough seas that actively move the player is perfect! I want a 99% game over, but with a real possibility of survival. Like an irl rip tide. They don't automatically kill you, miracles can happen, but you're probably dead.

Great video. You have one of the best and most informative channels on the internet! Love to watch your stuff!

Me, small brain: *Lerp it for smoothness*

Happy new year Acerola! Great vid as always)

At 16:00 I would recommend a dashpot/damper rather than a spring, I don't wanna overexplain if you know what it is, but basically instead of resisting based off distance like a spring, it resist motion from its current point, this prevents it from being pulled to the normal and instead allows it to drift around without being erratic

15:40 If you measure and plot the normal vector angle fluctuations, and then tune the spring and damping constant so that the angular spring has a similar resonant frequency, the motion won't be quite as smoothed out. Alternatively, if you all you want is to keep the buoy upright, you could apply a similar angular spring to the physics-based system. That way you could keep the nice angular displacements, while having a tunable parameter that keeps it mostly upright.

Ayy new Acerola video! Happy New Year

I think adding a little blip noise when notes/corrections are put on screen would be helpful because I'm a listener not a watcher and wouldn't know what I heard was incorrect unless I saw the screen.

Dude your videos are so good. Your timing between images is impeccable

Hey, i made something similar a year ago. I was inspired by a part of the sea of thieves documentation, were they talked about having a complex visual ocean (gerstener waves) based on a more simple combination of sine waves. So my solution was having a nice looking shader(back then only shdergraph, bc i just started on cg) and calculating the the hight of the water with the biggest waves represented as sine waves. it looked nice and was really easy on the pc(my plan is to redo that stuff at somepoint and make the vr sailing expierience or puking simulator).

I love this video because the topic is one of the most obvious things that regular game players haven’t ever thought about. How I went my entire life without questioning how they make things float in games is wild

what a nice way to end the year with another acerola graphics adventures

For the more realistic simulation a thing that came to mind that would give quite a bit of artistic control and shouldn't be that much heavier to compute, just have a buoyancy multiplier for the voxels/areas and then you can easily make different parts of the object more or less buoyant. With that just making the top more or the bottom less buoyant should make the buoy auto correct unless it's completely inverted.

It’s a bad game if the developers don’t take into consideration Quantum Entanglement.

Very nice. I imagine that if the object wasn't interactive you could simulate it all in a shader.

that's so cool, acerola. happy new year. edit: i just watched an entire ad read because cat videos were playing off on the side. genius?

Happy New year bro love your Christmas special

Why did acerola have to go so far with the longterm situationship? Definitely hit a bit too close to home for me😂

You could set a linear interval to sample the gpu requests to smooth out the raw data coming in. That could be a "sample rate" variable that you can set wherein a higher sample rate is more accurate but has more noise, whereas lower sample rates result in less accurate but smoother motion. You could also simply bake the motion if the object is static. Since the sin waves won't change at that exact position after a each cycle.

i love your vids SO MUCH! thanks, Acerola.

I learned something new, the video is enjoyable, and there is variety of options presented! 🎉 10/10 video

A physics video starting with a monogatari reference? What kind of dreamscape did i just stumble upon

TBH buoyancy feels so unpredictable IRL because of all inertia that I can imagine that this spring physics with some tuning will give believable effect. The fact that delay didn't affect subjective feeling only shows how much one can cheat on this.

An interesting idea is to just combine them both! Have the cheaper method applied on buoys far away, where accuracy is not the greatest concern, and then when the buoys enter a close range of the player, switch it to physics mode.

I feel like doing as many FFT computations as there are voxels in the object to get the water height only at that point might not be too expensive to do on the CPU, as long as the grid is sort of coarse.

I always get such a happy feeling of excitement when this dude uploads I love the silly and random cool and interesting programming videos, it's so fun!

It would be interesting to see how the amount of voxels, (and maybe their shapes & distribution in the cube) changes the simulation. Great video as always !

You need to set your center of mass on the buoy to be lower to automatically correctly avoid the stuck on its side problem and apply the force at the voxel position not at center of mass. It will then naturally want to tip to an upright position.

Another banger! Man I like this channel!

there was no need for the long distance relationship gag because that literally happened to me and now I'm crying great video tho

Running waves simulation on CPU is perfectly fine, until you calculate it only for some positions (where bounce objects are located). And you may avoid computing waves with length less than object size.

Very entertaining. It seems that this is a case where the delay is not only helpful, but you want more of it. Because water is compressible, objects (especially heavy objects) don't react immediately to changes in height or direction. Thus you could send some portion of the changes into an "accumulator" that would release an average of the changes. I did this with a flight sim where I wanted to add a little lag into the time between inputs and results - to reflect that controls wires stretch and contract (like springs) and air is compressible. It worked like a charm. That might just be the tweak that you need.

One idea is to do a bit of time smoothing so that the CPU snapshot has less intermittent effects. Sure, it'd make there be more latency between the water movement and the buoy movement, and you'd have to draw the water to a texture to do the time smoothing on the GPU side, but maybe it'd make up for it with the buoy being less noisy

But Acerola?? How do you make these informative and entertaining videos about an obscure topic that is very hard hard to learn?? On a serious note your channel just became my favorite, thanks for all the hard work!

You can cut your simplified cylinder with the water plane and find volume and center of mass of the submerged part. That gives you a bouyancy vector. You can do a series expansion on cpu to get the value in single point.

cant wait to see you fully simulate the wind forces and buoyancy of a pirate ship having the sails and rudder actually work

Incredible. This is inspiring and really well done. As an audio guy looking to begin game dev, I wish there was a channel just like yours but for us audio nerds… but as you know in the industry, who gets their data compressed and cut first? Audio 🤣 thanks a million for the inspiration!

If you only have a few objects, wouldn't calculating the y-position from the xz-position (and time) on the cpu be better than sending it from the gpu? Or did your new waves not really support that compared to the sin waves? Or is it still too expensive?

It amazes me how similar is sound/music field to video game/grogramming. All these algorythms pretty much work the same but with different data. It makes me optimistic that if i understand one i'll eventually undarstand another.

great video, great explanations 10/10

you are such a legend, i love your videos

For the voxel aproach you dont need the volume displacement for them. if we have a dence enough voxel field we can approximate the displacement by just sampling the waterhight.

Hey why you want use point upward force, basically I mean sample the ocean surface at some point divide by you then add upward force at point. Also gpu is better because it doing all vertex, but CPU can do that little times like 10 to 100 times with no problem. That mean no need to take data from gpu to CPU, just directly run the algorithm in CPU, also point that I mention is preferred by you, for me 4 to 6 point enough for your model

What i would've done is position an oriented bounding box for the buoy, represented as a model matrix, at the rough location where it should be floating. This matrix is passed to the GPU in a buffer. After the computing the water surface, you run a separate compute shader pass, which modifies the model matrix to simulate buoy displacement. In the final pass, you render the buoy geometry with the modified model matrix. No need to pass things back to the CPU. The beauty of this technique is that you can probably render a hundred buoys this way via manipulating their corresponding matrices in the compute shaders, then apply instanced rendering.

This was my final project for my computer animation class in my last semester of college

Beautifull! I loved the plot twist with reading data back from the GPU!, and seeing you go through a similar thinking process for bouyancy,, even though, i never went with the voxel approach for performance concerns, i did, stategically placed a number of "buoyant detectors" arround what i decided would be the bouyancy line of a given boat model,, theese detectoirs simply read a few data points for our ocean, and apply the bouyant force at a rigidbody at each detector location., if they are below the ocean water., they push up, and if not they fall, by gravity, wich ensures that the rotation of the bouyant object will match the waves outline arrount it, although that push up or down is running in cpu, is constantly in motion riding them with no lag. I love to see you took the simulation approach! Amazing!!

a monogatari and persona 3 ref in first few seconds, you have my sub

Maybe the "spring physics" lacks a bit of mass for the object. I believe you could add in the dynamics of the filter you're using to smooth it out, sort of like when you change the dynamic behaviour of a system using a PID controller

Acerola uploads, we watch.

Awesome video man, really interesting project and great script!

New acerola video!!

You mentioned that due to lag the buoyant force is sticking around for 5 times longer than it should. In the voxel simulation especially this made for some pretty wild movement on small waves. Would dividing the calculated force by 5 before sending it to the voxels result in a more subdued or maybe even more accurate result? I imagine a proper implementation would need to account for the current framerate to estimate the force reduction but it seems like a fairly trivial addition for what could be a significant fidelity boost. I may be completely misunderstanding the math though.

a nice relaxing Acerola video (I'm shaking and out of breath from grinding out AC6's NG++ final boss (I was so damn close last time))

I really like physics based buoyancy, it’s very satisfying to watch, but I understand how it’s not really realistic if you need a lot of buoyant objects. I’m honestly wondering how something like sea of thieves does buoyancy, since they need to have a lot of buoyant objects at once sometimes. I think for small objects they’re just setting the height position to the height of the water, but I’m not sure what’s being done for larger objects like ships, and I’m curious to know.

I feel like the last approach instead of treating it like its on a spring would be more visually interesting if instead of just setting the values to the height and normal vectors you had the buoy scale towards those vectors instead, if you could fix the calues to only be able to change at a specific rate then it would let the bouy move around within the constraints a lot more freely and with more fluid movement

Feels like spring has "too tough" coefficient. It takes several guessing iterations to find a nice look. At least in cloth simulation from scratch it took for me.

For the problem where the bouy could wind up on its side, you could add ballast, like a real bouy has. Essentially add an extra rigidbody near the bottom of the bouyant volume and put a bunch of the bouy's weight there. If you want it usable by a designer, you could add some code in the inspector that calculates the correct weight for the desired bouyancy and puts some fraction of that weight in the ballast. And to stop it from wandering, you could have an anchor, again like a real bouy has. It could be simulated as just a spring attached to the bottom that pulls the bouy back towards a desired position. I prefer physics based solutions to things if I can manage it. It takes some insight into how to translate that physics into simple tools that a layperson can use, but I really enjoy that process anyway.

Watching your videos with the sound off is like solving a rebus puzzle

Dang, God is really that powerful for creating ocean without any lag

Is there a way to step the orientation towards the new normal proportional to the dot product of the two? With the relatively limited scope of the orientations, it's unlikely to have to contend with gimbal lock, so the orientation won't need a quaternion if the normal doesn't use one.

That intro of flashing text reminds me of monogatari

3:50 was not expecting that to hit way that close to home for me. reopened some wounds there

Hey acerola. Wouldn't it be easy to smaple the water height at 3 points (similar to a bounding box) and then place the object on the center of the resulting triangle. I guess this would lead good orientation but maybe weird height (maybe combine with spring height)

The spring thing you mention towards the end sounds like a PID controller. Maybe that kind of implementation could lead to good results, but I imagine the implementation is somewhere between as expensive as the approximation and the voxel simulation so probably less desirable when you have many buoyant objects.

I just want to say Acerola’s cat + advertisement segment is the smartest thing ever.

get avg height of water in the area that's being touched, then lerp the results. movement up and down + rotation can be controlled with a variable. this also gives you control over the "sim", it's not going to look the best but it's certainly good enough in most cases.

i like how this video has floated to the top of my youtube suggestions. I hope it has the staying power to remain afloat and garner many views!

the long distance cpu and gpu relationship hit way too close to home and tells me that I'm still not really over my 7 year relationship... thank you for the happy new year video computer game png man