Cross-platform physics
games
Using MonoGame and
Farseer Physics
Rune Andreas Grimstad @runegri
Capgemini Norge

What to expect
• Lots of code!
• Intoduction to MonoGame and Farseer
• Playable demos
• Code on GitHub for you to play with :-)

What NOT to expect
• Deep dive into the features
• That would take days...
• 3D games
• Visit Richard Garside’s talk tomorrow at 11:40
• A complete game

Who am I?
• Rune Andreas Grimstad
• Lives in Trondheim
• Works for Cagemini
• Focus on .Net and anything mobile
• Programming since I was 8 years old...

Why games programming?
• Not my job!
• Fun
• Learning
• Becoming a billionaire after creating the next Angry
Birds Flappy Bird!

MonoGame
• Open Source implementation of XNA 4
• Runs everywhere
• C# / .Net
• Xamarin

Fez

Bastion

Draw a Stickman Epic

Transistor

MonoGame – getting it
• Download from monogame.net
• Clone from GitHub
• NuGet

MonoGame – features
• Supports all features of XNA4 (more or less)
• 2D
• 3D
• Content pipeline
• Input
• Sound and music
• Networking
• It’s a bare-bones framework…

Enough background!

How MonoGame works
- The Game Loop
Initialize and load
content
Update
game state
Draw
everything
Unload content

How MonoGame works
- Creating content
• Most file types are supported
• Either use an XNA content project
• Requires XNA Game Studio, so Windows only
• Create a MonoGame Content project
• Or use the MonoGame Content Builder
• Runs everywhere
• Not 100% done yet, but getting close

How MonoGame works
- Loading content
• Using the ContentManager.Load method
• Usually Content.Load<Texture2D>("spaceship");
• You can also load other resources this way
• SpriteFont, SoundEffect, Song, and so on
• Store the files in the Content folder in your project
• Build Action – Content
• Copy to Output Directory – Copy if newer

How MonoGame works
- Drawing stuff
• Use the SpriteBatch class
• Start with SpriteBatch.Begin
• Do your SpriteBatch.Draw calls
• End with SpriteBatch.End
• Try to limit how many SpriteBatches you use

Demo 1
• The basics
• Draw a sprite on screen
• Content
• Animation
• Camera, pan & zoom
• Input

Demo 1 – What did we learn?
• Game loop
• Content
• SpriteBatch
• Texture atlas
• Camera
• Input

All that from this little guy!

But there is more

Farseer physics
Farseer Physics Engine is a
collision detection system
with realistic physics
responses.

Farseer physics
• 2D Physics simulation
• Collision detection
• Objects with any shape
• Friction and restitution
• Joints
• Gravity
... and more

Farseer physics – getting it
• NuGet
• Download from
https://farseerphysics.codeplex.com/
• Build from sources
• The easiest way to combine with MonoGame?

One thing to be aware of
• Farseer uses the KMS system (Kilo, Meters,
Seconds)
• Use the ConvertUnits class
• Init with SetDisplayUnitToSimUnitRatio
• Use ToDisplayUnits and ToSimUnits
Your screen
Display coordinates: 1920 x 1080 pixels
Farseer coordinates: 19.2 x 10.8 meters

Demo 2 – more Bubble Bobble!
• A simple platformer
• Simulates a world
• Sprites are bodies in the world
• Collision detection
• Movement
Bubbles!

Demo 2 – what did we learn?
• Using Farseer!
• Worlds
• Bodies
• World and display coordinates

More features of Farseer Physics
• Polygon shapes
• Turning an image into a polygon in the game world
• Complex objects
• Combining many shapes into a single object
• Joints
• Attaching bodies to each other

Demo 3 – Exploring the cave
• Stupid game with lots of physics
• Polygon objects
• Complex objects
• Disabling gravity
• Attaching objects

Polygon shapes
Turn this... ... into this
MAGIC!

Polygon shapes

Complex objects
• Add many shapes to one body

Complex objects
• Join bodies using joints
• Revolute joints can be used to create a chain or rope
• Use the RopeJoint to set the length of the rope
• The possibilities are endless!

Finally
• There is much more to MonoGame!
• 3D – Richard Garside will talk about this tomorrow!
• Pixel shaders and effects
• Sound and music
• Use the SoundEffect and Song classes
• Input beyond the keyboard
• Mouse
• Touch
• Joystick

Finally finally
• Find my code samples on GitHub
• github.com/runegri
• And my slides on SlideShare
• slideshare.net/runegri

Get in touch
• I’m here for the rest of the conference
• Twitter: @runegri
• Email: rag@rag.no