crystal.Transition

Base class for transitions to inherit from. Transitions are used to decorate scene changes or camera changes. Some example transitions are color fades or screen wipes.

This class is of little use on its own as the default transition is an abrupt cut. You should implement your own sublasses, or use the built-in transitions described on this page.

Constructor

crystal.Transition:new(duration, easing)

The duration parameter is a number in seconds.
The easing parameter is an easing function, such as those provided in the math Lua extension.

local MyTransition = Class("MyTransition", crystal.Transition);

MyTransition.init = function(self, duration, easing)
  MyTransition.super.init(duration, easing);
end

local my_transition = MyTransition:new(0.2, math.ease_in_cubic);

Methods

Name	Description
duration	Returns the duration of the transition, in seconds.
easing	Returns the easing function used to smooth the transition.
draw	Draws the transition. This method is meant to be overridden.

Built-in Transitions

A few common transitions are included with Crystal.

crystal.Transition.FadeToBlack
crystal.Transition.FadeFromBlack
crystal.Transition.ScrollLeft
crystal.Transition.ScrollRight
crystal.Transition.ScrollUp
crystal.Transition.ScrollDown

These transitions can be constructed with duration and easing parameters. Their default values are 0.2 seconds and math.ease_linear.

Examples

This example uses the ScrollRight built-in transition:

local old_scene = MyScene:new();
crystal.scene.replace(old_scene);

local new_scene = OtherScene:new();
local transition = crystal.Transition.ScrollRight:new(0.5, math.ease_in_out_cubic);
crystal.scene.replace(new_scene, transition);

This example reimplements the FadeToBlack and FadeFromBlack built-in transitions:

local MyFadeToBlack = Class("MyFadeToBlack", crystal.Transition);
MyFadeToBlack.draw = function(self, progress, width, height, draw_before, draw_after)
  draw_before();
  love.graphics.setColor(crystal.Color.black:alpha(progress));
  love.graphics.rectangle("fill", 0, 0, width, height);
end

local MyFadeFromBlack = Class("MyFadeFromBlack", crystal.Transition);
MyFadeFromBlack.draw = function(self, progress, width, height, draw_before, draw_after)
  draw_after();
  love.graphics.setColor(crystal.Color.black:alpha(progress));
  love.graphics.rectangle("fill", 0, 0, width, height);
end