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GM Arcball Camera

A Blender-like viewport camera for GameMaker

To get started:

  1. Simply import the script to your project.
  2. Create the camera struct in an objects create-event like this: cam = new arcball_camera();
  3. Set the cameras projection matrix using cam.set_projection(_proj)
  4. In that same objects step-event call the update function like this: cam.update();
  5. In that objects draw event you can then apply the camera using cam.apply();
  6. Have Fun! Default values can be changed inside the script.

The controls mimic that of the Blender view-port camera fairly accurately.

  • Holding the middle-mouse button you can orbit around the target position.
  • If you hold shift with the middle-mouse button you will instead pan against the viewing axis.
  • The Number pad buttons will snap the camera to be axis aligned, except for 2, 4, 8, 6, which rotate the camera on the View-Up and View-Right axis respectively.
  • The scroll-wheel will zoom the camera in and out.

Things to note:

  • This camera uses a combination of quaternions and vectors all represented and stored in small arrays. This script would be much cleaner using a seperate vector/quaternion library though for the purposes of an all-in-one solution I included everything needed for the base system inside of a single script.
  • Over-writing values (specifically the vectors) inside of the camera every frame can cause issues such as cause Gimble-Lock, which is one of the primary issues this camera is intended to avoid. If you do this make sure you know what you are doing.
  • If you want to modify the way the controls work then you can simply look for the control() function inside of the script. You will find the default controls in there.
  • The dir value in the struct is misleading, and points from the center to the view_pos rather than the opposite.
  • The intended use of this is primarily as a convienent system for quick prototyping or to use while showing off other systems.

Pro Tip! I recommend setting up an input response for the period-key that resets the target_pos of the camera to the position of a selected object. This has been a very useful shortcut for me, and is also based on Blender as well.