Orthographic camera functionality for the Defold game engine
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README.md

defold-orthographic

Orthographic camera API for the Defold game engine. The API makes it super easy to convert screen to world coordinates, smoothly follow a game object and create a screen shake effect. This project is inspired by the camera component of the Phaser engine.

The project is shipped with an example that shows all the features of the orthographic camera. Test the example app in your browser.

Installation

You can use the orthograpic camera in your own project by adding this project as a Defold library dependency. Open your game.project file and in the dependencies field under project add:

https://github.com/britzl/defold-orthographic/archive/master.zip

Or point to the ZIP file of a specific release.

Basic usage

Add the camera.go to a collection. Depending on your use case you can either add the camera as a child of a game object to have the camera always follow that object or you could add the camera as a root game object and move or animate it manually using code or using the Orthographic Camera API (see below).

The camera will send view projection messages to the render script while it is enabled. Make sure your render script handles this message! See the section on render script integration below.

Configuration

Select the script component attached to the camera.go to modify the properties. The camera has the following configurable properties:

near_z (number) and far_z (number)

This is the near and far z-values used in the projection matrix, ie the near and far clipping plane. Anything with a z-value inside this range will be drawn by the render script.

zoom (number)

This is the zoom level of the camera. Modify it by calling camera.zoom_to(), go.set(camera, "zoom") or go.animate(camera, "zoom", ...). Read it using camera.get_zoom() or go.get(camera_id, "zoom").

projection (hash)

The camera can be configured to support different kinds of orthographic projections. The default projection (aptly named DEFAULT) uses the same orthographic projection matrix as in the default render script (ie aspect ratio isn't maintained and content is stretched). Other projections are available out-of-the box:

  • FIXED_AUTO - A fixed aspect ratio projection that automatically zooms in/out to fit the original viewport contents regardless of window size.
  • FIXED_ZOOM - A fixed aspect ratio projection with zoom.

Note: For the above projections to work you need to pass the window dimensions from your render script to the camera. See the section on render script integration.

Additional custom projections can be added, see camera.add_projector() below.

enabled (boolean)

This controls if the camera is enabled by default or not. Send enable and disable messages to the script or use go.set(id, "enable", true|false) to toggle this value.

offset_gui (boolean)

This controls if the gui should be offset during a screen shake or a camera recoil. This will send the camera offset to the render script using the send_camera_offset message.

follow (boolean)

This controls if the camera should follow a target or not. See camera.follow() for details.

follow_target (hash)

Id of the game object to follow. See camera.follow() for details.

follow_lerp (number)

Amount of lerp when following a target. See camera.follow() for details.

follow_offset (vector3)

Camera offset from the position of the followed target. See camera.follow() for details.

bounds_left (number), bounds_right (number), bounds_top (number), bounds_bottom (number)

The camera bounds. See camera.bounds() for details.

deadzone_left (number), deadzone_right (number), deadzone_top (number), deadzone_bottom (number)

The camera deadzone. See camera.deadzone() for details.

Render script integration

While the camera is enabled it will send set_view_projection messages once per frame to the render script. The message is the same as that of the camera component, meaning that it contains id, view and projection values. Make sure that these values are handled and used properly in the render script:

function update(self)
	...
	render.set_view(self.view)
	render.set_projection(self.projection)
	-- draw using the view and projection
	...
end

function on_message(self, message_id, message, sender)
	if message_id == hash("set_view_projection") then
		self.camera_id = message.id
		self.view = message.view
		self.projection = message.projection
	end
end

An alternative approach is to ignore the set_view_projection message and directly read the view and projection from the camera in the render script:

local camera = require "orthographic.camera"

function update(self)
	...
	local camera_id = id of your camera
	render.set_view(camera.get_view(camera_id))
	render.set_projection(camera.get_projection(camera_id))
	-- draw using the view and projection
	...
end

NOTE: In order for this to work you need to make sure that the Shared State setting in the Script section of game.project is checked (defaults to checked)

Feeding window size to the camera

It is recommended to send the window width and height from the render script to the camera module. This is required if any of the projectors provided in camera.lua is used. It also allows custom projectors to get the current window size by calling camera.get_window_size(). Set the window size like this:

local camera = require "orthographic.camera"

function update(self)
	...
	local window_width = render.get_window_width()
	local window_height = render.get_window_height()
	camera.set_window_size(window_width, window_height)
	...
end

NOTE: In order for this to work you need to make sure that the Shared State setting in the Script section of game.project is checked (defaults to checked)

Window vs Screen coordinates

The camera API allows you to convert to and from world coordinates. This is useful when positioning a game object at the position of the mouse or knowing where in a game world a mouse click was made. The API supports conversion from both window and screen coordinates.

Screen coordinates

This refers to the actual mouse pixel position within the window, scaled to the display size specified in game.project. These are the values from action.x and action.y in `on_input()``

Window coordinates

This refers to the actual mouse pixel position within the window. These are the values from action.screen_x and action.screen_y in on_input(). Window coordinates should be provided as is, without compensation for High DPI (this will be done automatically).

Example render script

The orthographic/render folder contains a render script that does the above mentioned integration of the Orthographic Camera API. Use it as it is or copy it into your project and make whatever modifications that you need.

The Orthographic Camera API - functions

The API can be used in two ways:

  1. Calling functions on the camera.lua module
  2. Sending messages to the camera.script

camera.shake(camera_id, [intensity], [duration], [direction], [cb])

Shake the camera.

PARAMETERS

  • camera_id (hash|url)
  • intensity (number) - Intensity of the shake, in percent of screen. Defaults to 0.05
  • duration (number) - Duration of the shake, in seconds. Defaults to 0.5
  • direction (hash) - Direction of the shake. Possible values: both, horizontal, vertical. Defaults to both.
  • cb (function) - Function to call when the shake has finished. Optional.

camera.stop_shaking(camera_id)

Stop shaking the camera.

PARAMETERS

  • camera_id (hash|url)

camera.recoil(camera_id, offset, [duration])

Apply a recoil effect to the camera. The recoil will decay using linear interpolation.

PARAMETERS

  • camera_id (hash|url)
  • offset (vector3) - Offset to apply to the camera. Defaults to 0.05
  • duration (number) - Duration of the recoil, in seconds. Defaults to 0.5

camera.get_zoom(camera_id)

Get the current zoom level of the camera.

PARAMETERS

  • camera_id (hash|url)

RETURN

  • zoom (number) The current zoom of the camera

camera.zoom_to(camera_id, zoom)

Change the zoom level of the camera.

PARAMETERS

  • camera_id (hash|url)
  • zoom (number) The new zoom level of the camera

camera.follow(camera_id, target, [lerp])

Follow a game object.

PARAMETERS

  • camera_id (hash|url)
  • target (hash|url) - Game object to follow
  • lerp (number) - Lerp from current position to target position with lerp as t. Optional.
  • offset (vector3) - Camera offset from target position. Optional.

camera.unfollow(camera_id)

Stop following a game object.

PARAMETERS

  • camera_id (hash|url)

camera.deadzone(camera_id, left, top, right, bottom)

If following a game object this will add a deadzone around the camera position where the camera position will not update. If the target moves to the edge of the deadzone the camera will start to follow until the target returns within the bounds of the deadzone.

PARAMETERS

  • camera_id (hash|url)
  • left (number) - Number of pixels to the left of the camera
  • top (number) - Number of pixels above the camera
  • right (number) - Number of pixels to the right of the camera
  • bottom (number) - Number of pixels below the camera

camera.bounds(camera_id, left, top, right, bottom)

Limits the camera position to within the specified rectangle.

PARAMETERS

  • camera_id (hash|url)
  • left (number) - Left edge of the camera bounds
  • top (number) - Top edge of camera bounds
  • right (number) - Right edge of camera bounds
  • bottom (number) - Bottom edge of camera bounds

camera.screen_to_world(camera_id, screen)

Translate screen coordinates to world coordinates, based on the view and projection of the camera.

PARAMETERS

  • camera_id (hash|url)
  • screen (vector3) Screen coordinates to convert

RETURN

  • world_coords (vector3) World coordinates

camera.window_to_world(camera_id, window)

Translate window coordinates to world coordinates, based on the view and projection of the camera.

PARAMETERS

  • camera_id (hash|url)
  • window (vector3) Window coordinates to convert

RETURN

  • world_coords (vector3) World coordinates

camera.screen_to_world_bounds(camera_id)

Translate screen boundaries (corners) to world coordinates, based on the view and projection of the camera.

PARAMETERS

  • camera_id (hash|url)

RETURN

  • bounds (vector4) Screen bounds (x = left, y = top, z = right, w = bottom)

camera.world_to_screen(camera_id, world)

Translate world coordinates to screen coordinates, based on the view and projection of the camera. This is useful when manually culling game objects and you need to determine if a world coordinate will be visible or not.

PARAMETER

  • camera_id (hash|url)
  • world (vector3) World coordinates to convert

RETURN

  • screen_coords (vector3) Screen coordinates

camera.unproject(view, projection, screen)

Translate screen coordinates to world coordinates using the specified view and projection.

PARAMETERS

  • view (matrix4)
  • projection (matrix4)
  • screen (vector3) Screen coordinates to convert

RETURN

  • world_coords (vector3) Note: Same v3 object as passed in as argument

camera.project(view, projection, world)

Translate world coordinates to screen coordinates using the specified view and projection.

PARAMETERS

  • view (matrix4)
  • projection (matrix4)
  • world (vector3) World coordinates to convert

RETURN

  • screen_coords (vector3) Note: Same v3 object as passed in as argument

camera.add_projector(projector_id, projector_fn)

Add a custom projector that can be used by cameras in your project (see configuration above).

PARAMETERS

  • projector_id (hash) - Id of the projector. Used as a value in the projection field of the camera script.
  • projector_fn (function) - The function to call when a projection matrix is needed for the camera. The function will receive the id, near_z and far_z values of the camera.

camera.use_projector(camera_id, projector_id)

Set a specific projector for a camera. This must be either one of the predefined projectors (see above) or a custom projector added using camera.add_projector().

PARAMETERS

  • camera_id (hash) - Id of the camera to set projector for.
  • projector_id (hash) - Id of the projector.

camera.set_window_size(width, height)

Set the current window size so that it is available to projectors via camera.get_window_size(). Set this via your render script.

PARAMETERS

  • width (number) - Current window width.
  • height (number) - Current window height.

camera.get_window_size()

Get the current window size, as it was provided by camera.set_window_size(). The default values will be the ones specified in game.project.

RETURN

  • width (number) - Current window width.
  • height (number) - Current window height.

camera.get_display_size()

Get the display size, as specified in game.project.

RETURN

  • width (number) - Display width.
  • height (number) - Display height.

The Orthographic Camera API - messages

Most of the functions of the API have message equivalents that can be sent to the camera component.

shake

Message equivalent to camera.shake(). Accepted message keys: intensity, duration and direction.

msg.post("camera", "shake", { intensity = 0.05, duration = 2.5, direction = "both" })

stop_shaking

Message equivalent to camera.stop_shaking().

msg.post("camera", "stop_shaking")

recoil

Message equivalent to camera.recoil(). Accepted message keys: offset and duration.

msg.post("camera", "recoil", { offset = vmath.vector3(100, 100, 0), duration = 0.75 })

shake_complete

Message sent back to the sender of a shake message when the shake has completed.

follow

Message equivalent to camera.follow(). Accepted message keys: target and lerp.

msg.post("camera", "follow", { target = hash("player"), lerp = 0.7 })

unfollow

Message equivalent to camera.unfollow().

msg.post("camera", "unfollow")

deadzone

Message equivalent to camera.deadzone(). Accepted message keys: left, right, bottom and top.

msg.post("camera", "deadzone", { left = 10, right = 200, bottom = 10, top = 100 })

bounds

Message equivalent to camera.bounds(). Accepted message keys: left, right, bottom and top.

msg.post("camera", "bounds", { left = 10, right = 200, bottom = 10, top = 100 })

zoom_to

Message equivalent to camera.zoom_to(). Accepted message keys: zoom.

msg.post("camera", "zoom_to", { zoom = 2.5 })

enable

Enable the camera. While the camera is enabled it will update it's view and projection and send these to the render script.

msg.post("camera", "enable")

disable

Disable the camera.

msg.post("camera", "disable")