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A library for camera movement in the Ruby2D gem


~> 0.10
 Project Readme

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MIT License Ko-Fi

Ruby2D Camera Gem

With this gem you can easily add camera functionality into your games built with Ruby2D. Install it using gem install ruby2d-camera and then add it into your project with require ruby2d/camera at the top of your code, just below the line require ruby2d.

ruby run.rb to run the demo.

How to use the camera:

Create your object as if you would create it in Ruby2D except you need to prefix it with Camera::. For example to create a square you do Camera::Square.new. Any objects you create this way can be controlled and manipulated the same way that you control and manipulate them in Ruby2D with a few small additions. Any objects that do not have an x/y variable to move it now do have this, so that you may move the objects in the camera. Text objects also have a boolean that you can change named center which allows you to set the origin to be the horizontal center of the text rather then the edge.

To manipulate the camera there are 4 variables:

  • Camera.zoom Default: 1. This is a multiplier for how much you want the camera to be zoomed in(e.g 2 is 2x zoom, 0.5 is 0.5x zoom)
  • Camera.x and Camera.y Default: 0. This is the position the camera is centered on in the "world"
  • Camera.angle Default: 0. This is the angle of how much the camera is rotated(in degrees). It ranges from 0-360. Giving values outside of this range will automagically convert them to fit within the 0-360 range.

There are also 2 helpful functions:

  • Camera.coordinate_to_worldspace(x,y) You pass in the coordinates on the screen(for example where a player clicked in the window) and it will return the coordinates(in an [x,y] array) what the coordinates are in the world
  • Camera.coordinate_to_screenspace(x,y) You pass in the coordinate in the world(for example an enemy in your game) and it will give you the coordinates(in an [x,y] array) of where on the screen this character appears. Note this function may return values that are outside of the screen if the object is not in view of the camera

How it works:

A single Camera module exists which keeps track of objects created with it. When you create an object with the camera it creates a special object that inherits the original object from Ruby2D and then adds additional functions. The Camera module then uses these functions to draw the various objects on the screen each frame, using the parameters you gave it.


Under the example directory you can find a (poorly coded) demo using this gem. Simply ruby run.rb in the example directory to start the demo.


WASD to move character
Q/E to rotate camera
Hold R to reset the rotation
Space to enter doors

Known Issues:

Unfortunately text cannot be resized due to current limitations of Ruby2D, this will fixed when possible. This means zooming with text will look strange, centering the text somewhat alleviates this issue.