Game development for smartwatches

Problems and Solutions

Andrei Gradinari, Alexei CebanSpooky House Studios

Summer 2014• Google IO - google presents Android Wear (among other interesting things)

• Spooky House Studios ports 15 mobile games to the platform in 1 month

• Fancy code and project design in place by that time to do that

Winter 2015/2016• Spooky House Studios ports 15

mobile games to Tizen in 3 weeks

Some of Spooky House Wearable

Games

UI Challenges• Small screens• Small round screens• Small round screens with bottom

cut• Other shape of a small screen in

future ?

Porting challenges• Technical• UI• Controls• Maintenance of one more platform • Next step ( completely different

type of gaming, designed from the ground up for wearables)

Technical Challenges

• Performance - not an issue• PowerVR SGX530 series GPU on most Android Wear

watches• FRAMERATE = GPU FILLRATE / NUMBER OF PIXELS• Small resolution + iPhone 3gs power = HIGH

FRAMERATE• Network communications

• usually need to be done via middleman phone.• not transparent and not easy to use on Android

• Battery life - can be held under control. (Next slides)

Battery life• Sessions:

• 5 minute sessions at MOST (playtesting data) It’s not comfortable to play on watch longer

• couple of game sessions a day• doesn’t really hurt battery life

• FPS Limiter (smart implementation goes long way to power preservation)

Smart FPS Limiter must:• Keep FPS as low as possible when

picture is still• Increase FPS to 60 when there are

animated objects• Increase FPS to 60 when user

interacts• Response time shouldn’t be

affected. (Sleep thread for 1 second is not going to work)

Types of FPS limiters (slide 1)• Purely sleep() based:

• simple but very basic• Has Input lag , doesn’t allow for very low idle FPS

• Purely VSYNC based:• For ex: displayLink setFrameInterval: on iOS• Creates stable smooth FPS ( Fixed to 60,40,30,20,10, FPS

values)• Has input lag

Types of FPS limiters (slide 2)• Combined VSYNC with update() and render() not linked to

each other• Very responsive, no input lag ( at any FPS, even 1)• Smooth• Pseudo code example : The complex FPS limiter logic is

processed and returned as bool:bool needs_rerender = update(dt);if(needs_rerender){ render(); // also waits for vsync}

Examples of our smartwatch games

Before: After:

Gaming on smartwatches

• Classic control schemes don’t work• Swipe instead of drag• Tap anywhere instead of tap on specific

location• Alternative input (Digital Crown on Apple,

Rotating Bezel on Samsung Gear S2)

Wearable innovations that now are merged back into

our mobile games• FPS Limiter• UI Gestures• Simplistic UI Layout

Simplistic UI merged back to mobile

Same game. Different platforms

Handling reserved gestures

• Drag left-to-right is reserved on Android Wear

• Live with it ?• Or override it ( only make sure to

comply with Wear guidelines to be approved for watch category listing )

Nextgen wearable games• Extension of your smartphone / desktop / console game on your watch

• Notification driven (short sessions natural for wearables)

• “Lifeline’” is a good example of direction to move into:• Cross platform (Wearable & Mobile)• Natively limited session length due to the

nature of the game• Notification driven gameplay

Unique Ways of Input

• Pros: New natural way to interact with an app - always good.

• Cons: Not all touch screen input can be converted to limited native controls

Rotating Bezel + Physical Buttons ( Galaxy Gear S2)

Digital Crown - Apple Watch

Physical buttons ( Pebble )

Thank you!

• Next: Technical nuances, Alexei Ceban

Watch App types

• Apple-watch-like glance• Separate and independent app

Porting to a new platform

GraphicsSound File

System

Input Processi

ng

Project Templat

e

Basic App

lifecyclecallback

s

includes &

libraries

IrrlichtС++rules the world!

Running game: How to exit?

No swipes in the game Game with swipe controls H/W back button

Android Wear Tizen

MenuPower

Code allocation

Android WearTizen

Pebble

Graphics Library

Apple Watch

platform specific code

Sound

File System

Input Processing

C/C++

Java + JNI19%OpenGL ES

OpenGL ES

OpenGL ESObjective-C

Pebble GraphicsC

Spooky House game engine

C++81%

UI Adsin-app purchases

analytics

device capabilities

sounds & musicmathdownload upload

app lifecycle callbacks

support• Android: proper game quit tutorial• Android: detecting screen shape• Python script + rebuild.cfg• Setup Eclipse for Android Wear deve

lopment

Thank you!• Andrei Gradinari, Alexei Ceban,

Spooky House Studios• andrei@spookyhousestudios.com• alex@spookyhousestudios.com