VR GAME MODELLING
Creating games for VR is far from easy. The team at Epic Games share lessons learned from developing assets in Unreal Engine 4.14 for Robo Recall
Discover the challenge of creating VR models for games as Epic Games shares lessons learned from developing assets for Robo Recall
Increasingly we are being told that virtual reality is a growing sector, where CG artists can find new work, and explore new and creative ways to push modelling and animation. Video games and VR is one area you’ll want to explore.
Epic Games is at the forefront of promoting VR as a viable environment for CG artists. The latest game developed by Epic to promote new tools in Unreal Engine is Robo Recall, a spiritual successor to the company’s VR demo game Bullet Train.
Virtual gaming
Robo Recall has been developed by a team of 15 artists and programmers in one year in order to illustrate what can be done in VR using Unreal Engine.
“We wanted to explore what we can do in VR and we’re still discovering a lot. We learned a lot from the technical side, about how we can optimise the engine, what looks good in VR, what feels good in VR, and how we can have more characters with real shadows,” says art director Jerome Platteaux. “We also learned how to not make people vomit every few seconds!”
Developing Robo Recall – an arcade score-chasing shooter that pits the player against an army of robots and mechs – forced the team to reconsider how games are made and also how assets are modelled.
Lead technical artist Wyeth Johnson explains: “One thing that’s interesting about VR is that you can’t trust your game development instincts. A lot of things that you think look good in two dimensions don’t hold up at all when you’re really in the scene in 3D. We also had to retrain our eyes and how we think about art assets. You can’t intuitively do it either, you have to make something in VR and then realise why it’s not good.”
Scott Homer, environment artist on Robo Recall, says the need to bring models into VR to assess and develop within VR highlighted how important scale is to modelling assets for virtual reality. “You’d make assets and bring them into virtual reality and the effect of something being off would be instantaneous,” he says.
The key for the team was to iterate with very rough prototype models. Time wasn’t spent getting the concept perfect on a monitor and then going into VR. Instead, a rough concept was created, this prototype was taken into the Unreal VR editor, and once it worked in VR, it was taken to Zbrush to push the model.
“We focused on getting prototype meshes into VR as quickly as possible. So we’d have a rough concept and I’d make a rough model and then everybody would look at it in VR,” explains Scott. “We’d all give feedback and Jerome would make tweaks to certain proportions, and so we really had to be careful about how we used
our time, especially because it was such a short development cycle. So it was a lot of iteration up front and just iterate, iterate, iterate, and then get it in VR. And once we had it working in VR, then I could proceed to the high-poly detail modelling and all that good stuff with confidence that the final model would work as intended,” Scott continues.
But the team didn’t go in blind. Having previously created models for Bullet Train, the artists knew what the polycount should be, which for Bullet Train was 30,000 polys per character and no more that three sets of maps.
“One of the biggest challenges we faced was definitely staying within our budget for geometry, but also not being able to lean on normal mapping as much. And then that was compounded by the fact that you’re going to be right up close to these robots, so that you can rip an arm off and look at it inches from your face,” says senior mechanical artist Pete Hayes. “That’s the fun part about creating for VR, because you have that one-to-one scale relationship. It is amazing as a modeller to be able to walk up to a 12-foot robot that you’ve made and look up to it at 12-feet tall. It’s something you don’t get from traditional video games. But that also puts an immense amount, or a greater amount, of pressure on you as a modeller to have it all to scale. You can stylise as art, but we found you can’t really break scale in VR because that’s the biggest thing that breaks the experience. So as a modeller, it’s important to make sure that the thing feels like a one-to-one scale, believable object in this universe we’ve created.” Polycount Rules To meet the polycount, the team needed to get creative with how to use detail and maps, and it came back to iterating inside
Scale was vital to get right when modelling the robots, such as this boss character. the artists would take concepts into VR to judge scale and where the player’s view would be The fun part about vr is creating Things To scale Pete Hayes, senior mechanical artist, epic Games
Oculus using the Unreal editor. Environment artist Ignacio Guajardo Unanue says: “I think detail around the player’s point of view is very important. For example, there’s a lot of detail around the neck of the robots as we know that’s where the player is going to see the robot: its neck muscle. It’s very satisfying to see that in VR, to see these cables and tiny details is great.”
Again, the workflow of prototyping in VR meant the artists could gauge how best to use detail. “We would have our prototype meshes in the game and just see where we’re interacting with them the most, what parts of the model are you seeing the most. We would have a good feel just by our iteration process and our concept, and with the prototype meshes being in gameplay already,” says Pete. He explains this meant they knew that players were grabbing the chest and head a lot, so those areas became a focus for the artists. Likewise, players rarely looked at the robots’ feet, so they could save on polys in those areas. “And so, iterating through the prototype process helped us a lot in knowing where to spend that geometry.”
Scale soon became the defining factor when modelling, as it directly affects a player’s sense of perception: “When something is too small you don’t really appreciate it, and when something is too big you lose the sense of scale. If you go higher than 12 feet, the robots start to lose their sense of scale, they just look like giant polygons,” explains Jerome.
Again, every modelling and concept decision came down to how the robots looked in VR. “All the decisions we made about the robot models were about what
looks good in VR, not what looks cool for a robot,” says Wyeth. “The cool factor came after the player’s sense of scale and the right proportions, and then once those are good you can go and design the thing. I think that’s the most crucial thing about understanding developing for VR: you’re starting from a different place, at least as far as the concept goes.”
It seems that the Epic team are ahead of the curve when it comes to creating assets for virtual reality games. The Epic pipeline has been developed over several games and tech demos, to the point where the team can start a project with a clear workflow. “Technically I think the pipeline is pretty much there,” says Jerome. “File sharing can be cumbersome, but with the overall balance between normal maps, quality of textures, projection for numbers of polygons and textures we have, we start with a pretty good idea of what we can do,” he continues.
new Challenges
Building games for VR is as much about discovering what works in VR as it is about developing new techniques and technology. Unreal Engine is proving itself a versatile platform to work on, and only the burden of needing a very high frame rate can prove taxing. “Having shipped a lot of games, we understand the technical side of the pipeline,” says Scott. “These are questions like: how do I get a model in? How do I use normal maps? How do I texture?” He explains further: “The big question when we look at VR projects is what works for this completely new viewing paradigm? And that’s where our learning has had to come from; we are relearning form, rather than function.”
Developing environments for VR raises different challenges than when creating worlds for standard games. Presence is everything within virtual reality, and maintaining that illusion of
the team believe models assets such as environments and props will all be done inside VR in the years to come
reality is certainly central for game design and asset creation.
“Players’ perception is really different in virtual reality than in a normal 2D game, so when you think about level design, you have to really think about where you want the player’s attention to be,” says Scott. “And because we have a 360-degree visual experience and a 360-degree auditory experience, level design is really difficult in VR. At any given time, you have to guide the player explicitly to where you want them to be.”
To help both gameplay and presence in Robo Recall, the artists chose to base the levels on real-life environments – a city street with recognisable cars and phone boxes – to familiarise the player instantly. “For example, on the streets we have the correct proportions, we have cars and all of these little elements that give the player a sense of presence,” explains Jerome. “They don’t have to think about what is around them, they understand the volume of things very quickly and that helps the player. It also helps to be able to judge the distance between yourself and the robots. All of those little things add up and the player feels more comfortable more quickly in this environment.”
Another thing that the artists learned is that the sense of parallax or negative space is very satisfying in VR. “When you slightly move your head and you see a lot of things overlapping, that’s great to see. So we have a lot of negative space in the [robot] characters.
And we apply the same technique on the environments. So if you slightly shake your head, you’ll see a lot of parallax on the environment too,” says Ignacio.
The team also learned a lot about the use of specular. “Reflections are really, really different in VR,” says Scott, adding: “Your perception of the shape of the material is almost entirely defined by the shape of the
specular. It’s much more sensitive in stereo than it is in a 2D game, and so highly contrasting materials with really reflective elements next to really matte elements with broader specular highlights tend to be really satisfying and give you a really great perception of the curvature of the surface.”
This meant the artists could push the materials on the robots further than they would have in a traditional 2D representation. “It’s very nice to see the specular moving over the shiny parts of the robots, and just by moving a little bit of your head you can see all of those little details. That’s something we don’t get in regular games,” says Jerome.
When the team do hit a technical hurdle, they’re in the enviable position of being able to ask the Unreal Engine development team to create a solution. One new feature evaluates frame rate: where to optimise and how to optimise. Another new tool already available in Unreal Engine 4.14 is the forward renderer, which delivers very sharp images in the headset.
Creating shadows is also now easier than it was previously, as Jerome explains: “We have also optimised a lot for shadows... Now we can have the shadow of the character cast realistically in VR. This is something we’ve not been able to do before.”
Planar reflection is another new and exciting feature. For the demo Bullet Train, character reflections were faked by duplicating and inverting a character’s legs to make them resemble a reflection. “Now we don’t do that anymore, now we have a real reflection,” says Jerome, explaining: “We choose a character, select the character and include them in the planar reflection and get an actual real reflection. It looks awesome in the app and it grounds the character a lot more.”
the Future of unreal
All of these features and many more are available in Unreal Engine 4.14 or are coming down the line in Unreal Engine 4.15, due at the end of February. Jerome says that the team see themselves as “the first pass.” They are the people who “go through all of the problems and try to fix them and then integrate those changes into the engine,” he says, adding: “And now the next time we release the engine, these changes are going to be available for everybody to use. It’s good for the community.”