Ryan James Smith Profile picture
May 13, 2022 8 tweets 4 min read Read on X
1/N Some folks asked me to share my setup in #UE5 for how I used #Niagara to generate tiling ocean waves using Fast Fourier Transforms. This thread will hopefully shine light on the process and serve as a guide to those wanting to do the same. #gamedev #realtimevfx
The method for generating tiling ocean waves using FFTs can be summed up in these steps.
1. Precompute the h0 lookup table where each texel contains the encoded values needed to represent a wave. Its called h0 because that's the variable Tessendorf gave it in the original paper. Image
Everything needed for the sim is stored in this texture. From it, a wave's speed, magnitude, direction and frequency can be derived based on the Texel's location and the data stored within. The dark areas are from a "spectrum" that is multiplied to produce realistic ocean waves.
2. Precompute the "Butterfly Texture" which is essentially a lookup table that is designed for fast computation of the IFFT Algorithm on the GPU. The size of the texture is log2(N)xN - so a 512x512 grid would result in a 9x512 texture. Below is stretched for visualization. Image
3. Now, every frame I update the Fourier components so they animate with time, then they go through the horizontal, then vertical IFFT operations. This series of operations produces the 3D Displacement map that I use to derive normals and offset the geometry.
4. For foam, I take the Jacobian of the displacement which does a really good job of detecting when the vertices "loop" in on themselves due to excessive displacement. When this happens, I add foam, which is diffused and dissipated over time. I store it in the alpha of disp. map
5. Splashes are done by spawning particles where the foam goes above a specific threshold. They get an initial velocity that is in the direction of the wind, but that whole system can be improved with better math.

Here's an overview of the whole emitter that generates the FFT. Image
Here's the paper by Tessendorf
people.cs.clemson.edu/~jtessen/repor…

And here's the paper I referenced heavily for how to do the IFFT op on GPU.
tore.tuhh.de/bitstream/1142…

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More from @OverdrawXYZ

Dec 18, 2022
Since I'm on the AI topic, I want to point out some hypocrisy (probably unintential).
The below image was snipped from a post on @ArtstationHQ's front page. Somehow this guy thinks getting your art scraped by an AI is the same as being raped. Or are people using AI tools rapists?
It's kind of hard to tell, I'm sure it hits people hard and that's what it's meant to. It got a reaction from me, even though I don't really agree with the delivery but can understand the point he's trying to make, i guess.

Here's the part where it's fucking dumb.
This person's portfolio is filled with AMAZING illustrations. There's no doubt in that. But there are a TON of drawings of copyrighted characters. How is this different than a person with less skill using AI to produce images of their favorite characters?
Read 5 tweets
Dec 18, 2022
1/N
I wanted to say a few words about AI and what's going on with @ArtStationHQ . Normally I wouldn't comment, but as an R&D Engineer who has actual experience creating custom AI architectures at Gearbox and deploying them to artists, I feel like I can
add to the discourse in some meaningful way, rather than just be more noise. Disclaimer that these are my opinions and they don't represent the position of my employer or anyone I work with in any capacity. Also, let me say that I *understand* and *hear* artists who are
concerned about AI. There absolutely needs to be rules and laws set to govern what for profit AI companies can and cannot do. But we're not there yet - these types of debates aren't even happening at a legislative level, and if they are, they are about more concerning
Read 22 tweets
Apr 4, 2022
1/6 A year and a half later, I finally finished my black hole project. #madewithunreal and now powered by #Niagara, this shader/sim implements physically correct gravitational lensing, which bends the light in all kinds of groovy ways! #gamedev #realtimevfx #astronomy #UE4 #UE5
2/6 A weird phenomena of gravitational lensing is the photon-sphere. @ScienceClic hooked me up with the equations I needed to represent this. When done correctly, zooming the camera in yields the same image repeat over and over to infinity (it gets small though)!
3/6 The accretion disk was my main focus this time around. I ended up learning how to write fluid solvers because I didn't want a static texture that was just warping around the event horizon. I wanted something alive, dynamic and violent.
Read 6 tweets

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