How DreamWorks solved Troll glitter

How DreamWorks solved Troll glitter

Behind the scenes of ‘Trolls World Tour’

With each new film, DreamWorks Animation’s crew is tasked with an ever-growing list of animation challenges. For Walt Dohrn’s Trolls World Tour, one of the very particular requirements was glitter. A couple of characters were covered in it, as were some environments. While the studio had tackled glitter before, this time they wanted to do even more with it, including ensuring it was ‘part’ of the character.

In this befores & afters behind the scenes breakdown of Trolls World Tour, DreamWorks Animation visual effects supervisor Matt Baer outlines the glitter solution, and a number of other VFX challenges such as generating more photorealistic fabric, felt and fuzz textures, and doing fun things with crowds.

When some of your characters are basically all glitter

Matt Baer (visual effects supervisor): Glitter is a tricky thing to capture in terms of what each of those little mirrored surfaces are doing. We had to be really careful how we were even placing them on the surface of different objects, because all of a sudden now you have mirrors inside furry characters. Are those supposed to reflect the fur around it? It adds to the render complications as well.

 

We have so much glitter and, to be quite honest, probably one of the main things said in dailies was- ‘I wish there was more glitter or more sparkle in this shot’. I’ve never been on a show like that before. It turned out to be a joke – ‘Wish this had more sparkle!’

One of the challenges that we had on the first film was with a procedural texture glitter map. We designed, but around the mouth of a character where there’s lots of stretching on really extreme facial poses. You would see the actual glitter stretch.

In other films we had actually built sequinned dresses and that was something we’d looked at. But we didn’t want them to look like they’re covered in scales. So what we did was build and improve our glitter shader to analyze the amount of stretching. Then refer back to an object frame or a reference frame.

Even on those extreme poses, the little things that represented the glitter wouldn’t stretch, which meant that we didn’t have to go in and paint out those areas later on – they just actually worked coming straight out of the renders.

Having characters interact with an oasis of glitter

The effects department and our texturing department and matte painting all helped build a full desert oasis with distant hills basically covered in glitter. The patterns going through those were inspired by different fabric designs that came from the art department.

 

We wanted to also have the characters interact with that glitter as well. Something that we were playing with on the glitter, for example, was, as the characters would occasionally hold frames or move on a step-type of animation every once in a while, the effects department started playing with some of those ideas, too. That was a motion challenge – how do we make this glitter feel small or have the audience have the feeling that you’re seeing something that’s inspired by stop-motion.

One of the cool ideas that our effects department came up with was having some of that glitter be cascading across the ground or some of it might be cascading off a pile of glitter would be on ones and then other portions of it would be on twos. So at any given time you’d have this mix of the two together. So you’d still have a slight feel of a stop motion inspired effect, but at the same time you still have some fluidity to it because about half of the effect would be on ones.

Graphic equalizer crowds

We really were pushing crowds to come up with a unique choreography. Something that would really take you and be inspired by whatever genre that you happen to be seeing those crowds in. So as much as we would be doing a lot of layout and simulation with them, we really wanted them to integrate with actually whatever the light show that happened to be happening at that time or the music that you were hearing.

For the Techno Reef sequence, there’s more of an electronic feel, which means that it’s a little bit more precise, but at the same time we want everybody to know that we’re underwater. Crowds kind of took on both of those challenges.

The characters themselves are emissive – they create light in there. There’s somewhat of a light show being generated by the crowds. But what we wanted them to do was remind the audience that you’re underwater. So they came up with these ways of having these nice slow rolling waves to the crowd, but at the same time, the crowd is also a spectral analyzer, which is a way of describing the graphic equalizer you’d see on your stereo system.

Then for the hard rock scene

It was more like a mosh put, but more of a feeling of fun joy and not scar at all. We were looking at so much footage of these amazing outdoor rock concerts, and asking, ‘What is the Trolls version of that?’ We came up with these sea of crowds that look like they jumping up and down with the timing of what you would do if you were putting on a really crazy puppet show. So while there’s this intense pressure of this concert going on, you look out on the crowds and they’re in this mosh pit, but the way that they’re moving just so joyful just by the way that they’re moving.

More and more detail

We really wanted to push even further into the feeling that everything is made out of fabric and that it was ‘handmade’. On the first Trolls, they did a great job of giving the feeling that everything was mostly made out of felt. On Trolls World Tour, we really wanted to push even further and develop more and more ways of building more types of fabrics by actually physically building every thread, every type of blade of fuzz, which would help us sell the scale.

On Trolls, we had these fur procedurals that allowed us to grow fur on a lot of different things and that helped us build felt and it looked beautiful. We wanted to do that even more on Trolls World Tour. If we had to make silk or organza for the water or embroidery on a shirt or leather or denim or even a sweater, we wrote programs that would actually build those out of individual curves.

We wrote tools that would help our texturing artists do all sorts of embroidery, to do frayed edges on denim. And those are all represented as individual curves. Then that gave us this great sense of scale and made everything feel small, especially when you get in close to it.

But by creating all these curves, well, curves aren’t much different than hair as far as the renderer is concerned.

So in doing so, we were also making it more challenging for us to render the film. Which meant we had develop new ways for us at the studio to not completely flood our render farm with with these high memory jobs. Just rendering a head of hair on a normal film could be quite a challenge to actually get that to be a clean render to see each fiber. Now we were creating it everywhere! Even the faces of the trolls have hundreds of thousands of little blades of fuzz.

So, we wrote all these different tools that would analyze the scene and decimate the CVs on each curve depending on how far they were from camera. We’d ask, will those curves actually go through some sort of depth of field so we don’t need as much level of detail? It really forced us into new new ways of analyzing the scene to manage memory.

Behind the scenes of MoonRay

What our ray tracer MoonRay meant for us on Trolls World Tour is something that we’d always wanted to do with hair at the studio, which was to get more physically-based and natural-looking materials. If we just take the troll hair, for example, it allowed us to really get the light to scatter through in ways that we couldn’t before without custom tricks that we were used to faking the old render into doing.

It really helped us to really pick at details and get light to move through surfaces and through the hair in ways that we hadn’t before. We actually built new shaders for the skin of the trolls that would interplay with translucency, the fuzz that was geometrically built and then this kind of fake fuzz type of material that would emulate and serve as a good backdrop for the real fuzz that was there.

We also built all these new glint-type tools. A lot of the hair on the trolls is meant to be a kind of wool, and the way that that kinks is a little bit different than how a human hair would look. And so in our grooms, we would build a subset of the hairs that would pick up these glints that almost looked like the hair was turning at a more sharper angle. The new renderer really helped us pick up those details better than we had before.

Water and lava…out of fabric?

We didn’t want to create water the normal way and we didn’t want to create lava the normal way. So as part of the idea of going all-in on making everything out of fabric, we launched the effects department with actual samples of cloth. So for the lava, we handed them a bunch of samples of silk and a pair of scissors. And the idea was, if we couldn’t make the effect out of those two things, then we were doing something wrong.

So they went off and they built all these tools and they actually did build a miniature live-action shoot set-up for us where we shot high-speed photography with an air gun of these little silk and glitter blasts being launched up. That served as something that was really inspired to us.

On the backend we wanted to replicate the way that silk naturally moved. So we started playing different cloth solvers. At the same time we wanted to not have them completely move the way they would in the world; we wanted them to have a timing that was inspired by how the characters are moving, which is a little bit more of a stylized timing. So there’s lots of lots of tools being built that allowed our effects artists to run these cloth simulations, but then at the same time have complete freedom to re-time them re-time even portions of them in different ways.

VFX variety

I have to say there’s just so much variety on this show. On other shows, you’d figure out the aesthetic and you’d be like, ‘OK, now that we finished that sequence, I kind of know what to do on the next one.’ Not on Trolls World Tour. Every two months, it was like a new science experiment was starting. It was a great experience.

Looking for more behind the scenes on animated features? Check out The tech behind all those trees in ‘Frozen 2’

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