# Convert the position `x, y` on screen, to world coordinates on the plane at `target_z`
	#
	# `target_z` defaults to `0.0` and specifies the Z coordinates of the plane
	# on which to project the screen position `x, y`.
	#
	# This method assumes that the camera is looking along the Z axis towards higher values.
	# Using it in a different orientation can be useful, but won't result in valid
	# world coordinates.
	fun camera_to_world(x, y: Numeric, target_z: nullable Float): Point[Float]
	do
		# TODO, this method could be tweaked to support projecting the 2D point,
		# on the near plane (x,y) onto a given distance no matter to orientation
		# of the camera.

		target_z = target_z or else 0.0

		# Convert from pixel units / window resolution to
		# units on the near clipping wall to
		# units on the target wall at Z = 0
		var near_height = (field_of_view_y/2.0).tan * near
		var cross_screen_to_near = near_height / (display.height.to_f/2.0)
		var cross_near_to_target = (position.z - target_z) / near
		var mod = cross_screen_to_near * cross_near_to_target

		var wx = position.x + (x.to_f-display.width.to_f/2.0) * mod
		var wy = position.y - (y.to_f-display.height.to_f/2.0) * mod
		return new Point[Float](wx, wy)
	end