lump

Lump is a Flump runtime for LÖVE2D. It allows playing MovieClips exported from Flump through a Flash/Actionscript like API.

Animations exported from Flump are cleverly optimized:

• all of the animation component sprites are packed inside a texture;
• a json file describes clips and frame properties;
• one single animation can hold many different states (idle, walk, ...)
• the memory footprint is generally smaller than that of prerendered sprite animations;
• they're smooooth as flumps.

Status

The library has been in use for some time now in a game of mine, and seems to be pretty stable. Nonetheless, it may be improved in a number of ways. Please consider this beta status.

Demo

A simple demo playing Flump's logo animation is available in /demo. It requires Love2D 0.10.1

MovieClip API

Requiring and initializing

MovieClip = require("lump")

local json = "library.json"
local atlas = "atlas.png"

mc = MovieClip.new(json, atlas, 33) -- loads the given animation, playing it at given framerate

After initialization, the movieclip frame pointer is set at the first frame (1) of the first available clip.

Playing the animation

-- in love.update
mc:update(dt)

-- in love.draw
mc:draw()

Playback API

The api tries to mimick the original Flash API:

-- go at frame 1 of current clip, or first clip
mc.gotoAndStop(1)

-- stop at frame 1 of clip "walk"
mc.gotoAndStop("walk", 1) 

-- go at frame 1 of current clip, or first clip, then play
mc.gotoAndPlay(1) 

-- play from frame 1 of clip "walk"
mc.gotoAndPlay("walk", 1) 

-- stop / play
mc.stop()
mc.play()

MovieClip frame labels and events

Flump exports Flash frame labels, and the library offers a simple way to hook into the enterframe event. This way, it's possible to use labeled frames as triggers for actions in your code. All there is to do is to define .onFrameLabel function. The function will be called every time a labeled frame is encountered, and will be passed the label and the frame number relative to the current clip. A good example is playing a step sound everytime a character's foot is on ground:

mc.onFrameLabel = function(label, frame)
  if (label == "foot_left) then playSound("step_left") end
  if (label == "foot_right) then playSound("step_leftright") end
end

MovieClip transforms and properties

Two properties describe current animation state:

mc.currentClipName = "walk"
mc.currentFrame = 1

Movieclips supports transforms and uses love.graphics matrix internally:

-- Move so that the center is at 200, 200
mc.x, mc.y = 200, 200 

-- Rotate
mc.rotation = math.pi / 2

-- Scale
mc.scaleX, mc.scaleY = 2, 2

-- Flip on axis
mc.scaleX, mc.scaleY = -1, 1

Caching of animations

Everytime you build a movieclip, internally Lump creates:

• an animation definition, containing data for frames and clips;
• a movieclip object, which plays the animation.

For performance, Lump will cache animations so that every movieclip created with the same json and same texture will be actually pointing to the same animation definition. No duplicate animation instances will be created.