2 dimensions of awesome: advanced actionscript for platform games by iain lobb

Two Dimensions of AwesomeBy Iain Lobb

Two Dimensions of

Awesome.

I don’t have the

awesome.*

I’m looking for the

awesome.

*I’ve found some of it.

First, let’s troll…

The typical Flash game…

• Stickmen!• Arenas!• 20fps!• 550 x 400!

The retro Flash game…• 8-bit pixel art!• 2 frame animations!• Tile grid!• Everything is a square!• Double pixels! You want to see those

pixels, right?• 3rd party engine!

Now let’s see what they’re doing on games

consoles…

Ray Man Origins

Limbo

The 2D awesome…• HD graphics.• 60 frames per second• Smooth scrolling camera. • Multiple layers of parallax.• Uneven, organic terrain.• Expressive character animation.

BunnyMark• 26x37 pixel sprite• 30fps• 640x480

Demo #1BunnyMark - Bitmaps

4000 bunnies

Demo #2BunnyMark - Blitting

6000 bunnies

Demo #3BunnyMark – HTML5 Canvas

2000 bunnies

Bunny Domination!

BunnyLandMark• A more realistic scenario• 30fps• 640x480• 26x37 pixel sprite• Scrolling world• Depth-sorted sprites

Demo #4BunnyLandMark – Bitmaps

22,000 bunnies

Demo #5BunnyLandMark – Blitting

90,000 bunnies!

Now something shocking…

Soylent Green is people!

BunnyMark is a lie.

60 fps

Demo #6BunnyMark – Bitmaps (60fps)

1500 bunnies

Demo #7BunnyMark – Blitting (60fps)

1500 bunnies

HD resolution• Typically Flash game = 640x480• Portal maximum = 800x600• Nitrome = 500x500 pixels• Rayman Origins = 1080p =

1920x1080• 500x500 can fit into 1080p eight

times!

960x720

Demo #8BunnyMark –

Bitmaps (60fps)960 x 720

1000 bunnies

Demo #9BunnyMark –

Blitting (60fps)960 x 720

1000 bunnies

Sprites• 256x148•Digital painting• Scale +/- 50%• Rotation

Introducing PirateMark!

• 60 fps• 960x720• 256x148 sprite• Scaling +/- 50%• Rotation• How many sprites can we have?

Demo #10PirateMark –

Bitmaps (60fps)

…

20 pirates

Demo #11PirateMark –

Bitmaps (30fps)

40 pirates

Demo #12PirateMark –

Blitting (60fps)

15 pirates

Demo #13PirateMark –

Blitting (30fps)

80 pirates

Stage3D

Demo #14PirateMark –

ND2D

20 pirates

Demo #15PirateMark – Genome2D

80 pirates

Demo #16PirateMark –

Starling

100 pirates

Demo #17PirateMark – haXe NME

150 pirates

Demo #18PirateMark –

HTML5 Canvas

0 pirates

100 pirates

He who controls the graphics card

drivers, controls the universe!

Can we support Stage3D and

software rendering?

Can we support 30fps and 60fps?

// Frame-based Euler

function update(){ speedY += gravity; speedX *= drag;

speedY *= drag; x += speedX; y += speedY;}

// Time-based Improved Euler

function update(time:Number){ speedY += gravity * time; speedX *= Math.pow(drag, time); speedY *= Math.pow(drag, time); x += (speedX + oldSpeedX) / 2; y += (speedY + oldSpeedY) / 2; oldSpeedX = speedX; oldSpeedY = speedY;}

Demo #19Improved

Euler

...or fix your time step and interpolate.

Camera and Parallax Scrolling

• A 2D camera is just an X and Y offset.• Subtract the camera position from

each sprite’s world position to get its screen position.

2D Camera

// Simple 2D Camera

for each (var sprite in sprites){ sprite.x = sprite.worldX – cameraX; sprite.y = sprite.worldY – cameraY;}

• By using a container sprite we can make this process even simpler.

• Set the container position to negative the camera position.

• Each sprite will automatically get the correct screen position.

2D Camera

// 2D Camera using container

world.addChild(sprite);

function update(){ world.x = –cameraX; world.y = –cameraY;}

• To enable zooming, we add a second container.

• We move the inner container and scale the outer container.

Zooming

// Zooming 2D Camera

world.addChild(sprite);container.addChild(world);

container.x = stage.stageWidth / 2;container.y = stage.stageHeight / 2;

function update(){ world.x = –cameraX; world.y = –cameraY; container.scaleX = container.scaleY = zoom;}

Demo #21Zooming Camera

• To enable parallax, we position the inner container to negative the camera position, multiplied by a fraction.

Parallax

// Zooming 2D Camera with parallax

world.addChild(sprite);container.addChild(world);

container.x = stage.stageWidth / 2;container.y = stage.stageHeight / 2;

function update(){ world.x = –cameraX * 0.5; world.y = –cameraY * 0.5; container.scaleX = container.scaleY = zoom;}

Demo #22Parallax Camera

Demo #23Starling Camera

Uneven Terrain

hitTestPoint(x, y, shapeFlag);

Demo #24hitTestPoint

hitTestPoint• Only works +/- 2000 pixels• Lags by one frame if you move the container.• Must be on the stage but doesn’t have to be

visible.• Reduce number of calls using AABB broad

phase.• Same principles can be applied using

getPixel32

Bullet

Arrow

Fast moving bullet

Character

Character

Grenade

Grenade

Grenade

Grenade

Demo #25Projectiles

Collision Detection• Box2D / Nape• Straight lines• Why hitTestPoint?

Level Editor• Position objects• Rotate and scale objects• Draw collision areas• Give instance names for code access• Save, Save As, Undo, Redo, Copy, Paste• Zoom

It’s Flash Professional!

It’s Flash Professional!

It’s Flash Professional!

It’s Flash Professional!

Parsing with ActionScript

• Create instance of level• Loop through children.• Determine type of child using

“is”• If no linkage found, assume

terrain

Gotchas

• Small scroll area – scale down and zoom in

• “Invalid size and position”• Flash CS5 crashes creating large SWCs• Expensive

Character Animation

Timelines leak memory!

Sprite Sheets

• Flash, After Effects, Blender• Great performance• High memory use• Not changeable at runtime

Bones• Not the Bone Tool!• Separate sprites for each body part• Saves memory• Adjustable playback speed• Customizable• Parse timeline – animations are pure

data

Demo #26Bones

Demo #28Alice Gameplay

Final thoughts…