FX Adventures in Uncharted 4: A Thief's End

NEILAN:
I've been a Dynamics Artist at Naughty Dog for just over five years now, I moved here from South Africa. "Dynamics Artist" is a weirdly specific title, but I'm basically a Technical Artist who's geared towards physics simulation. I create and script realtime physics objects that react to the character in the game, as well as pre-baked destruction and simulations, usually in Houdini. I also do tool programming for our 3D packages to support other artists.

How long have you been using Houdini?

When and how did you first come to discover Houdini in the world of 3D?

NEILAN:
Weirdly enough, aside from very briefly for university projects, Houdini was my first real exposure to working in 3D at all. I came at the industry from a programming angle, which is maybe why Houdini seemed like such a natural fit. My previous studio hired me to be a tools programmer, but they had a small but growing department of Houdini enthusiasts. Houdini seemed exciting to me, so I did everything I could to learn it when I could.

RAY:
I found out about Houdini from my school, Savannah College of Art and Design, where they taught two courses in Houdini. I spent a winter break learning the basics before starting the courses, which were taught by the prestigious Ken Huff. Previously I had been a general CG artist, using 3D software like 3ds Max as far back as middle school, but Houdini was a completely different way of thinking. Once I went Houdini, I never looked back.

What are some past projects you've done prior to joining the prestigious ranks of Naughty Dog?

NEILAN:
When I left in 2010, BlackGinger had done a lot of high profile commercials and three international films. Most of them featured Houdini effects heavily, lots of RBD, particle and smoke simulation work.

RAY:
I previously worked at Rhythm & Hues, The Mill, Psyop, Method Studios, and a few others. I did a mix of commercial and box-office work including Life of Pi, Percy Jackson: Sea of Monsters, Hercules, and the iPhone 5C reveal.

Then we have proprietary tools to script our particle behaviors and custom shader writing packages for the complex materials our FX use in-game.

NEILAN:
Our pipeline is largely Maya based. Generally, whatever we work in has to be converted to a Maya scene to get it into the game. When I first joined, I was one of maybe three people at most who used Houdini at all, so I wrote a lot of scripts for getting our game data between Maya and Houdini. That's about the extent of my workflow, as I'm usually working in one or the other, but the studio at large uses a lot of ZBrush and Substance.

NEILAN:
On my end, I'm mostly using Houdini to create pre-baked animations, either through DOPs [Dynamic Operators] or SOPs [Surface Operators], which then get transferred to our engine via joint animation in Maya. On a game like Uncharted 4, that's mostly rigid body fracturing and destruction. Then there were a few little SOPs networks for things like cloth deflations and moving liquids.

Initially I tried to just use the raw flow from the simulations but there were always issues that I would have to paint over or redo. Drawing flow curves is very meditative :-). I would then paint in the flow intensity and wave height to suit the environment and gameplay. The end result was a texture with flow direction and intensity in RG channels and wave height in the B channel.

I would also export a normal map and alpha map to improve the look of the river. Once the textures were ready I would need a bounding box set to generate the in-game meshes, which was easy to deduce and export within Houdini ROPS [Render Operators] (right image).

All that, coupled with a water uber-shader, written partially by me, gives us in-game rivers and oceans (see images below). In the end it was a relatively cumbersome pipeline that I plan to renovate and streamline for the next Naughty Dog title, both art side and pipeline side. It is worth mentioning though that once you had a set of textures in the game for a river you could paint in Houdini and have it update in-game relatively quickly, making art iterations pretty smooth. We don’t have a game ‘editor’ of any sort so this was the next best thing.

Something we could never do with the traditional skinned actor pipeline. In production we made most birds, and some ground animals with vertex animation, we even made a background crowd for the city tower background.

Eventually, we developed a python toolset out of Houdini so other artists could use the system, as our geometry files are based on Maya scene files and more difficult to integrate with Houdini than something like Unreal.

NEILAN:
There are a few wall breaks and collapses in the Madagascar market fight, as the truck's crashing around, those had to be done on a strict time schedule for E3, so that was tricky. There's this wooden rope bridge that breaks in the island chapter ("At Sea"), which took a while. The animation for the character running and jumping had already been done, so it was a lot of very specifically timed glue and constraint breaks of planks and ropes. To make things worse, it transitions to a real-time physics setup halfway through the collapse, so it had to hit very specific poses and velocities to keep the transition as smooth as possible. That took a long time to get right.

NEILAN:
When it comes to fracturing, I use two different approaches. Either I'm cutting very precise shapes to match a texture (or because the sequence happens close to camera), which means I'm cutting by hand, usually in Maya. For larger jobs (or where the texture detail is some distance from camera) I rely on Houdini for fracturing. I made an HDA that encapsulates a lot of my routine workflows for clustered fractures, and adds edge detail as efficiently as possible.

NEILAN:
Forums, mostly. The SideFX forums and OD|FORCE are great resources!

NEILAN:
When I started at ND in 2011 (mid Uncharted 3), we'd been using Houdini 10 - I think that's the earliest version that had been used at the studio - and we used Houdini 15 to finish out Uncharted 4.

NEILAN:
I wish I'd had more time to take a proper look, but I love the look of the new modelling tools. I'd also love to play around with the crowds stuff - that's a personal interest of mine, and I'd love to find a work related reason to dive in too. :)

RAY:
I haven’t had a chance to play with Houdini 15.5 yet, and the new features don’t really pertain to my work, but I’m sure 16 will have some cool new features I could use.

NEILAN:
I wish I felt more inclined to do more cloth work in Houdini. Truth be told, it might just be that I haven't really gotten to grips with the FEM solver, but I find that I'm more likely to stick to Maya for cloth, as it makes our workflow easier. I also think there's a lot I don't like about rigid body solves right now. It's hard to beat Bullet for speed, but I find it can be too volatile to get stable, good looking results close to camera. It's hard to go back to RBD given the speed difference.

RAY:
I think it would be nice to have some kind of super optimized version of the smoke and flip solvers which reduce the flexibility and customization for making fast, simple simulations. A lot of work I see my coworkers make in FumeFX are relatively simple setups but are in general easier to populate and quicker to sim in that package. I know the shelf tools have been getting better and we do have partial GPU simulation, but they should keep pushing that area for more streamlined setups.

NEILAN:
Every now and then on the forums I catch a glimpse of some of the systems people are creating great work with, like crowds, or sand/fluids/pyro and I super wish I had the time to play around with those solvers! Otherwise, playing other AAA games, and seeing what other VFX studios are doing with technical effects is really inspiring.

RAY:
I personally find inspiration in a lot of the SIGGRAPH white papers and dev talks with other game studios. They’re a bounty of bleeding edge technologies that may not necessarily be ready for everyday use, but are definitely something to aim for in terms of future innovations.

NEILAN:
Stick with it! I don't think it's unfair to say there's a relatively long learning curve with Houdini compared to other packages, and that can be discouraging, but if you put in the time to understand its systems thoroughly, it absolutely pays out. Also, learn Python/VEX!

RAY:
I would tell people learning Houdini to try to do as much as possible without simulations. Learning to do things with just SOPs will make you a way more in-depth user than someone who just runs simulations all day.

RAY:
Game wise, I’m a fan of adventure, strategy, roleplaying games. My favorite recent games have been Overwatch, Stellaris, Fallout 4, The Witcher 3, Metal Gear Solid: Phantom Pain, oh and Uncharted: A Thief's End :-)