November 21, 2018
How Evasion pushes VR shooters forward with innovative combat and high-production values
While VR introduces a heightened sense of immersion coupled with new mechanics, Rooke notes that it poses new developmental hurdles, "There are also many challenges to overcome. You are always mindful of frame-rate and camera motion to ensure players don’t get sick, and you want to try to make sure that players’ movements in game match one-to-one with their body movements. If they swing their arm, they expect that to match perfectly in game," Rooke explains. Failing to do so can make combat feel clunky and break immersion. The lead game designer continues, "This can be tricky in situations where players are dual-wielding two controllers, but in-game, they’re holding a two-handed weapon, or in melee games, when a player slashes a solid object, nothing stops their real arm’s motion, but in-game you’d expect the blade to meet some resistance on impact." Rooke adds, "So there’s lots of prototyping and trial and error. This is not that different than traditional console development, but it can be a longer process before you’re happy with your mechanics, and you might have to go back to the drawing board more often than you’d prefer."
Combining time-tested gameplay with modern tech, Evasion draws inspiration from arcade classics like Galaga and Space Invaders. "It was the concept of dodging and blocking projectiles in VR that we liked. We didn’t want to simply soak up damage from instant-hit weapons. It’s really fun to navigate a hail of lasers flying your way. So we looked at old-school shooters as well as more modern bullet-hell games for inspiration," Rooke stated, adding, "This gameplay marries well with high-intensity, fast-paced shooter combat featured in games like Doom and Destiny. The idea is to throw overwhelming odds at you while providing you with over-the-top weapons to fend off the swarms of enemies," Rooke continued.
Players will be able to wield these over-the-top sci-fi weapons as one of four "Vanguard" classes, which are basically elite super soldiers. As Rooke notes, "You’re almost unstoppable as most enemies on their own do not provide a big challenge," but the adage "strength lies in numbers" certainly applies here with Rooke adding, "there are so many of them and they’re relentless."
In prototyping the insect-like alien enemies, known as the Optera, Archiact borrowed a page from VR shooter Space Pirate Trainer by having a few flying drones shoot projectiles at players. Rooke adds, "Then we thought it would be fun to not only dodge them, but also block them with a shield." Thus, the inclusion of a shield became a core defensive mechanic of the game. Rooke continues, "It seemed like a natural thing to try. The loop of dodging, ducking, blocking, and shooting was simple and fun." Rooke expands on how the gunplay and weaponry evolved from here, "As we polished the mechanic, it became more and more fun. We decided to give the player a few weapon pickups as temporary power-ups. Players could grab weapon cores out of the air, similar to our [current] power cores and health cores, each one providing a more powerful weapon with limited ammo. Once the ammo is expended, your default weapon returns. The weapon power-ups included a spread shot, burst fire, auto fire, laser, chain lightning orbs, and a slow moving nuke. This was our demo — one class with multiple weapon power-ups."
While this prototype started with a single character, after demoing an early build, Archiact found that testers wanted different classes that would fit varying playstyles and archetypes. Rooke explains, "Some people said they wanted to be more of a support or healer class, while others still wanted to destroy everything in front of them. So we took what we liked best about the various weapons and used them as a starting point for the four classes. The spread shot turned into the Warden’s primary fire, while the nuke was nerfed down and used as his grenade launcher. The laser and default blaster inspired the Striker, while the burst fire inspired the Surgeon. And, of course, the chain lightning orbs gave birth to the Engineer class. Each class has a unique way to finish off the enemy with a Tether Lash mechanic, and each also has a unique support buff that’s applied while they’re healing their teammate [online]."
With four distinct character classes to choose from, Archiact had to ensure each of the Vanguard were fun and balanced. Rooke notes, "There’s the DPS (damage-per-second) output of each class to watch, while giving various shield sizes and health values to each class. The Warden has the most health and largest shield, and deals a ton of damage up close, but is less effective at long range. The Striker has fast and precise shots, and can strafe faster than the other classes, but her shield is the smallest, and she has the smallest health pool."
Regardless of which class players pick, they'll be confronted with several campaign missions chock full of enemies to overcome. Developer Archiact honed in on VR's ability to provide player movement agency as a focal point for gameplay and challenge. "The way to succeed is to fight really hard like you would in a game of paintball. Once you get used to moving and dodging and being mindful of every projectile flying your way, it will click," Rooke stated, adding "We made mission one exciting, but not overly challenging. Players can take their time to get used to their weapons and become accustomed to taking advantage of their charge shots and tether-lash mechanics to finish enemies off. Mastering the loop of destroying enemies and pulling in power cores to level up your weapon is key. By mission two, the action starts to get more intense. This mission is like graduation from training. If you can survive this mission, you should be ready for the rest of the campaign." Rooke adds, "The enemies get progressively harder as the 'elites' are introduced in the later missions, and some boss battles add some tough spikes. With only one difficulty mode (at launch) the key is to get good at the game in the first couple of missions. Retrying them a few times is acceptable and expected until you get the hang of it."
Adding to the immersion of the missions are the game’s destructible environments. Archiact used UE4's integration of the Apex destruction system to incorporate this. Archiact Software Engineer Thomas Edmunds noted the benefits of this approach, "[It] not only allowed us to heavily customize how destructibles look, but also to optimize them for different platforms and LODs (levels of detail)." Edmunds added, "This was important because destructibles can be very expensive and we did not want to sacrifice the ‘cool factor’ for performance."
While Evasion features high-production values with great animations and detailed backgrounds, the road getting there wasn’t easy considering the indie developer only had five artists. This issue is compounded by the fact that the studio needed to optimize the game to meet VR's steep performance requirements. Not only do VR games need to be rendered at a high resolution, but they need to run silky smooth, or judder can occur. This can cause motion sickness for certain players. Archiact Senior Modeler Austin Huntley elaborates, "We had to be very diligent about staying on [performance] budget. Running on the PS4 in VR at 60 FPS constant requires you to look closely at every aspect of your game in detail to cut down and minimize performance costs. You have to make trade-offs and find a lot of creative solutions to problems. Transparency is a good example. We created shields with thin faded grids to give the illusion of a transparent energy shield instead of a large plane."
To meet VR's steep performance demands, Archiact had to really think outside the box. For instance, Evasion features a level with an open outdoor environment that features a lot of bullets and enemies, which can create a draw-call nightmare. To overcome this, Huntley explains, "We used a lot of mesh instancing as well as shared atlas materials to reducing the amount of both material and mesh draw calls."
Intelligently synergizing optimization with game design was another elegant move Archiact made. Huntley elaborates, "Early on, we made targets for enemy performance and the cost of any combination of enemies on screen." By thinking ahead in this regard, the senior modeler remarks, "This helped our enemy performance stay consistent and more predictable in any combat situation by limiting how many could be spawned based on this budget."
The game's visuals and immersion are enhanced due to Evasion's use of full-body avatars. This is noteworthy considering that, with only three points of contact, many other VR games simply opt to render a virtual head and floating hands. To achieve a believable full-body, Archiact leaned on inverse kinematics (IK) by IKINEMA, but Edmunds added that "UE4’s versatile animation Blueprints allowed us to layer and blend locomotion and detail animation, such as trigger pulls with the IK model." Considering Evasion supports traditional VR motion controllers and singular peripherals like PlayStation VR's Aim Controller, this implementation was particularly helpful with Edmunds adding, "It also allowed us to support one-handed and two-handed animation sets for our different platforms."
While maintaining a high, consistent framerate is paramount to mitigating simulation sickness, some players may feel nauseous by the use of free movement. This is an undesirable effect that stems from joystick locomotion which causes the eyes to be out of sync with one's inner ear. Thankfully, Evasion offers numerous movement methods for those who want your standard run-and-gun action and for those who have yet to get their "VR legs." As Rooke notes, "Everybody is different and there’s no getting around that when it comes to VR. Some people have iron stomachs and some don’t. Instead of declaring that we’re catering to a specific crowd, we thought it would be best to provide robust accessibility options so everyone can feel comfortable and ‘at home’ in our game. More and more people want the authentic experience of running around in VR like they would in a traditional game, so of course we delivered a free movement option." To ensure that this method was as friendly to stomachs as possible, Archiact employed a few tricks, "The key to making this option comfortable is to keep the camera motion constant and smooth. Strafing and reversing is slower, which is what your brain naturally expects. Most important, this helps prevent nausea," Rooke stated.
For those that can't handle this free motion method at all, Archiact implemented an innovative dash-step option. "It works really well as an alternative," Rooke says, adding, "It’s like little mini jumps forward instead of a gliding camera motion. Between these two options, most people can play the game comfortably." As a more inventive, immersive option, the developer also incorporated a mode that allows players to jog in place. "It's similar to free move, but requires an up and down motion from the player’s head as if they’re jogging on the spot." This mechanic allows the inner ear to more closely align with what the eyes see and Rooke asserts, "This makes it feel like you’re actually running around in the world and further helps to reduce discomfort." Rooke exclaims, "It’s also a fun way to get exercise."
Making It Unreal
As an engine for virtual-reality production, Edmunds praised UE4, stating, "Unreal Engine 4 is a great choice for VR development, since it provides you with a complete VR framework to work within, while allowing you the freedom to change things to suit your projects needs." The software engineer continues, "Each VR platform’s subsystem is nicely contained, and totally open for changes once you hit the inevitable weird ‘edge case’ as your project progresses."
Edmunds highlighted Blueprints coupled with the consistency and extensibility within the engine that eased development, "Having all sorts of tools integrated right in the engine makes workflows so much faster. Even the destruction assets and cloth assets have tools in the editor, which was incredibly helpful."
The studio used Blueprints "extensively" exclaimed Software Engineer Jake Moffatt, "Many of our systems are highly customizable within a Blueprint’s default values, using UPROPERTIES to surface complex data structures that are easy for designers to use." The software engineer added, "We also made great use of Blueprints for scripting our missions. We have many custom nodes for stringing together mission-specific events, including many that use the Blueprint Async Action pattern, which we found kept our mission scripts very intuitive to read."
With online co-op being a major feature of the game, Archiact leaned heavily on Unreal Engine 4's networking features, "Our team made great use of the UE4 Network Profiler tool during development to ensure that we weren’t using excessive amounts of bandwidth," Moffatt stated.
Considering Evasion is available across PlayStation VR, Oculus, and Steam, Edmunds noted how UE4 made the game easier to port, "Unreal Engine 4 nicely abstracts away many of the platform differences. In VR development, however, some of these differences require different gameplay systems that translate to a need for ‘un-abstracting’ certain things. Handling all the different input systems, and each platform’s own requirements for VR, was a significant challenge that was made manageable by Unreal’s subsystem framework."
Interested in experiencing Evasion for yourself? The game is currently on sale in celebration of this week's Steam sale event. It's also available on the Oculus and PlayStation stores. For more information on the game, check out www.evasionvrgame.com and follow the title on Twitter and Facebook @evasionVR.
If you would like to experiment building your own VR game, download Unreal Engine for free today.