This Project Shot has been in the works since June, there's been 3 iterations of, this is the third! I started working on this before I worked for Platige/Juice on War Thunder, However it was really low res as I was just testing at this stage. Then when I finished on WarThunder I started working on the second iteration and even did the first renders, but it was not looking good enough, so I decided once I got more free time I would start from scratch and make it the best I could, I don't settle for second best!
I wanted to create my most ambitious FX Fluid Shot based on a Kaiju Breaching from the water, Godzilla/Pacific Rim Style. Igor Zanic also did a shot like this last year. Also now with RealFlow RenderKit for 3DS Max 2014 (RFRK) I can now render Mist, which adds so much realism to Fluid Simulations (more below on mist). This is also my first ever project using Houdini (Houdini was not used for final Fluid Sims). I was aiming to get as Photo-Real as Possible, to create a believable FX Shot.
First Iteration, Very Low Res, Originally From Early June (2014)
This shot had quite a few problems to overcome, I'll do my best to explain them!
The Kaiju is Modelled and Rigged by Sean Buck & Robert Campbell, I've had this rig since last year and wanted to wait until I was good enough to do a Kaiju Breach Shot. The animation I did in Maya, its really simple, just the Kaiju breaching through the surface, not jumping though, kinda whish I had him jumping and splashing back down.
The Kaiju Mesh itself has a few problems that caused Flickering Particles as the Kaiju passes through the surface, this was due to bad iso surfacing, LuisM from Next Limit released a really good tutorial on working with different iso surfaces, I did some RnD using Shell Mode however the results were not as good, so after running several low res sims under different cell size's I decided to stick with Solid inside as the flickering was only there for a few frames and on the end of the sim, so I decided to shorten the sim as a compromise. I found out its due to the skinning in Maya, so If I use this again I would need to look into re skinning the rig. The texture for this I quickly painted in Mudbox.
Flashing Particles On Breach
In RealFlow I setup the Hybrido Core Fluid and after a previous tests I really wanted to get an Epic Splash, To get the really nice push and displacement of the core fluid theres no way of relying on the Kaiju's collision only, so I used Bounded Noise and Vorticity Boost, the Vorticity Boost makes a huge difference and is one of the most valuable settings in RealFlow Hybrido. I used 25.0 which made a huge difference, the Bounded Noise was animated to be high value as the Kaiju Breaches and then fade out over the rest of the sim, these combined work really well for a realistic splash in the Core Fluid. I really liked the look of the Splashes done by ILM for Battleship when the Stingers first breach out the water, Ofcouse there sims are much more detailed and complex!
Left is with no Bounded Noise and no Vorticity Boost, Right Is With animated Noise, and Vorticity Boost of 25.0
Next Problem was again related to the bad Kaiju geo, because I was using a KVolume Daemon as most cases you don't want the Fluid Colliding with the container sides, But because of the bad Iso Surface it was causing Fluid to slowly escape, so with the help of Particle Sampling and (Later on in Max and Comp Hiding the edges) I got over this problem.
See Particles Escaping, Overcome with Particle Sampling (New In RF2014)
The Final Core Fluid Simm contained around 30 Million Particles, Took 12-13 Hours on my PC (I7 8 Thread, 16GB Ram, GTX660), My PC is quite slow in terms of FX work, Soon to change! Next was onto the Secondary Sims, Splash was first. I Originally tested using FLIP For Splash, but I changed to Ballistic (Dumb) because I wanted a more dense splash sim, The splash sim uses a stronger Gravity Daemon than the Core Fluid to avoid the splash flying off and looking fake. For the Foam I used the new Bubbles Emitter in RF2014, its really nice and within a bit of tweaking it created really nice foam.
Ballistic Splash Sim
FLIP Based Bubbles/Foam Sim
Next for the Mist sim I tried using the splash to drive the mist, however it got to dense and started to look like smoke, also the sim times per frame were awful, so I setup another splash emitter that was really low res only siming around 30-40,000 Particles, this was then used to drive the mist sim with High Dissipation. Mist adds so much realism as it simulates when high speed water droplets (Splash/Spary) Particles break up in the air. The Mist sim turned out nice, however I wanted to try something I saw on the Odforce Forums, so I exported the mist to Houdini via VDB, then emitted more mist and re exported it as VDB. Its my first time using Houdini in a shot, And I know its only a small use, but it really helped the final shot. Also Houdini was used as quick way to preview sims because RealFlows playblasts are very slow compared to exporting to Houdini and running a FlipBook.
Final Fluid Sim Passes
Back in 3DS Max, I loaded my Core Fluid PRT Files via Krakatoa and used Frost to mesh them, the Final Fluid Mesh was very hires, I suffred lots of complete PC Crashes. I used Zhu/Bridson and squeezed as much detail into the mesh as possible. The PRT Loader was using a Magma Modifier to Colour by Velocity, For the first time I used Extra Tex Map using a Vertex Colour Map to export the velocity pass aswell as a Refraction pass. From this I could control how much whitewater I wanted in comp (Thanks to Adam Trowers for help on this). Its worth the extra work to get the White Water at high velocity, I think when CG Fluid sims fail is when the water shaders don't work, if you look at a big splash in real life you see the water moving at high Velocity and Vorticity turns white due to bubbles under the surface, so using Krakatoa and Frost you can simulate this.
Frost Mesh Testing
Showing How Much Realism Velocity Shading Adds
There were a few edge errors due to the deleting particles, however messing with the Blend Radius sorted this out. (Also looks worse in the viewport due to only displaying half res).
Frost Mesh Artifacts, Sorted at Render Time
I Rendered through V-Ray to get the Velocity (ExtraTex) Pass and Refraction Pass. The Kaiju was also rendred in this beauty pass so all the Refractions and Reflections were accurate. The Fluid Mesh waves were made using Noise and HOT, and copied onto an Extended Ocean Plane. The Splash and Foam passes were rendered in Krakatoa and the Mist Was rendered using RFRK through Mental Ray using AutoVolume. The Frost Mesh was NOT used as a Matte Object only the Kaiju. I used Boxes with a Matte Material on for the Frost Mesh Pass in front of the edges to fake the Open Boundaries Mesh (See Above Screenshot).
Final Render Times were done on my Nights after working on my new FX Job I don't know the exact times, but I know the Fluid Mesh Pass/ Kaiju Beauty pass took around 25 Mins Per Frame.
There was a lot of Compositing for this to blend all the sim render's together and combine the Fluid Mesh to the Extended Ocean. To Do this I used a few animated masks and the paint erase tool to soften the edges.
Blending the Fluid Mesh to the Extended Ocean
Compositing the velocity Pass to create the white water is very simple, I have the Refraction Pass of the Fluid mesh in a separate comp and then I add the ExtraTex/Velocity Pass ontop and lower the opacity depending on how white I want the white water. Then I blend this comp into the main Fluid mesh using Screen Blending Mode. I had to manually mask the velocity pass with a lot of feather to slowly fade the velocity pass in after the flickering of the initial breach, but also because it was effecting the whole surface of the fluid mesh, so manually masking the splash area only is the way to go! This is pretty much invisible due to the Splash, Foam and Mist passes hiding it. Same for the Splash Pass, Masking the flickering out where the Kaiju mesh is and lots of feather, but by then the Velocity pass is hiding that, so theres lots of masks going on to hide the errors!
Colour Correction On The Splash Pass
Velocity+ Refraction Pass to create White Water Shading In Comp
A lot more CC later, one really nice thing I did was add some noise/grain to the mist render to kinda create the look of particles rather than looking to much like smoke, it also helped bring out the detail.
I added some Camera Shake and Zooms to add more Movement to the Final Shot
For the Final shot I made a short breakdown showing the Render and Sim Passes, Theres a lot to be improved on my Next Fluid sim shot, but its a big step since my last (The UFO Crash), A lot of the problems were due to the bad geo/Skinning of the Kaiju, that's what caused the flickering, so it caused for lots of masking and feathering the passes together in comp, they saved the day!
I really like how the Final Sim looks, the Mist Really adds a lot to it, It was nice to use Houdini and VDB for my first time. Also the ExtraTex Map Velocity shading really helped the Final Shot! Back to doing World War FX now. More Info Soon!
