Camera

Outcome / Goals

In this guide we’ll:

• Learn about the camera modifier
• Learn to transform the camera
• See how to use a 3D or 2D camera

Camera is a modifier

Camera exists within a World, and is attached to an Entity like other modifiers. You can attach a camera to an entity using Camera.create(entity).

var camera = Entity.create(world)
Camera.create(camera)
Camera.set3D(camera, 60, width/height, 0.1, 100)

You can have as many Cameras in the world as you need, they don’t have a cost to exist. A camera stores settings for it’s view and can be used to render any world.

The World.render function accepts an entity with a Camera attached. This makes it easy to render the same world from different angles at different times.

Transform driven

Camera uses Transform to decide where it will be positioned/oriented. Moving the camera around uses Transform.set_pos and related tools. It also means linking the camera to another entity is possible, and using other Transform related tools and modules to work with a camera.

You can use lerp (linear interpolation) to have a camera smoothly follow a player.

var target = Transform.get_pos_world(player)
var pos = Transform.get_pos_world(camera)
//Math.lerp2D for 2D xy only
var now = Math.lerp3D(pos, target, speed * delta)
Transform.set_pos(camera, now.x, now.y, now.z)

Default camera

Each world keeps track of a default camera. This is typically the one rendering uses. This is also how camera management code can switch, and how game code can interact without having access to the specific camera at all times.

Coordinate spaces

The camera controls how we perceive the game world and has a big role.

Space Conversions

The camera provides conversion functions, like:

• World Space to Screen Space
• Camera (view) space back and forth
• Clip space and more

You will often need to convert in order to make a game. Examples being:

• Displaying an entity position on the HUD
  • game world -> screen space -> ui world
• Converting mouse coordinates from window space to world space

Transform spaces

Because camera has a projection as well as a Transform, it has it’s own space conversion functions in addition to Transform space conversion tools! Use the camera ones when dealing with a camera where it makes sense.

The meaning of World Space

The units in the game world are given meaning by us, as a choice! We typically use the camera to do that but it’s one part of it. Make sure you know what coordinate space choice is made in your game.

A camera defaults to 2D set to the window size when created.

In a game, you control how much of the world you see using the camera.

Here’s some examples where being intentional can make game code easier:

• Pixel art games with a fixed size like 320x200

  • The camera displays 320 units x 200 world units on screen
  • The extra space is handled by letter box or pillar box, or backgrounds
  • This allows using known/relative units everywhere in game code

• A word game or match 3 with a 10 x 10 grid

  • Camera shows 10 units vertically (plus hud space)
  • 10 being at the bottom, origin of 0, 0 being near the top
  • The width is calculated from the fixed units, and pillar boxing or backgrounds can be used to cover the extra space
  • This makes your game code much simpler: 1 unit is 1 letter/grid item

• Similar in a 3D grid based game

  • All game code treats the space as 1 unit = 1 grid space
  • The camera is configured to present that to the user

2D and 3D helpers

You can switch a camera any time between 2D and 3D using Camera.set2D and Camera.set3D. Some functions are 3D specific, like FOV specifics, and some are 2D specific, like zoom2D related ones.

Camera blending and cuts

The Camera provides a few blend functions, as well as cut functions to work with multiple cameras. The default camera can be blended/cut between other cameras easily. This is sometimes called virtual cameras, where you have one definitive camera, but use others as virtual. You can switch the default camera to cut as well.

Camera frustum culling

A camera doesn’t do culling automatically unless asked. Like most things in luxe, your project outline might be configured to automatically cull for you.

This also means you control when and what is culled, allowing you to cull from one camera, but view the world from another to debug culling issues.

Editor Visualization

The luxe editor will show what a camera sees when selected, as well as showing the frustum. You can also pin a camera view and keep it showing while doing tweaks, and you can have multiple open as needed.