Here are some insights from that little project:
Easy things first.
I reused the animation from my T. rex museum breakout:
The environment is an HDRI from the asset browser. The lake (or river) is just a reflective plane with animated noise, and a gradient in the opacity channel to fade it softly into the backplate HDRI.
The trickier part was the simulation, naturally.
I wanted to simulate only the top layer of water, and I needed to figure out a way to only simulate particles in the area around the dinosaur. A whole lake would have been way too many particles of course.
At first I tried to simulate it only in a "pool" that was a bit bigger than the T. rex, using the liquid fill emitter. It worked, but I had visible splashes at the border of the pool - unfortunate if you want the transition between simulation and the rest of the lake as seamless as possible.
Instead of walls, I then gave the pool a slightly rising floor towards the edges.
That helped mitigating the splashes at the border.
However, I still had the problem that the liquid spreaded out pretty fast and drifted away from the dinosaur, where I actually wanted it to be.
The beauty of the new liquids is that they work so seamlessly with the rest of the particles system: I could just use an attractor force in the center of the dinosaur. With the right settings, it helped keeping the particles near the T. rex, while still allowing it to act like a liquid.
Here's the cached particles with the collider geo:
trex_water_v007_Viewport.mp4
The sim contains 3.7 million particles. I used the liquid fill emitter with a radius of 0,7 cm. Sim time was IMHO very reasonable on my RTX 4090, around 20 mins for 150 frames. I would have liked to simulate even more particles, but when I lowered the radius to 0,6 cm (= 6 million particles), I didn't even see the first frame after waiting for several minutes, so I quit that.
The cache is 27 GB. I only cached velocity, color and radius, which helped to reduce the size.
I then used the liquid mesher with pretty much the default settings, but smaller influence scale, a lot more smoothing and the droplet size set to 10% - that really helps getting rid of those huge blobs that often appear. Here's a clay render, liquid mesh only:
trex_water_v007_Clay.mp4
The particle color is mapped to the velocity, which was very handy to fake whitewater. I just remapped the particle color with a ramp to diffuse and reflection strength. The faster the particles, the brighter they are. I rendered them as a separate pass and added it on top in comp.
Those particles render crazy fast! A few seconds per frame for 3,7 million particles with motion blur... that was a real joy.
trex_water_v007_Whitewater.mp4
16
16
1
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now