Learning Gideros (and Lua) : Porting Advanced AS3 Animations code

Today I had a chance to play with Gideros SDK. In order to get a better understanding about the SDK and Lua in general, I decided to port some AS3 code. Here are some code from Keith Peter’s book, Advanced AS3 animations, in Lua.

I haven’t fully understood Lua so these code might look bad in the eyes of Lua experts 🙂 but at least it works.

[note color=”#FFCC00″]You can get the original, fully commented AS3 code from http://www.apress.com/9781430216087[/note]

First, the Vector2D. I don’t know if Lua has a built-in Vector class, maybe it does but as part of the learning process, I wrote one myself. Porting Vector2D.as to Vector2D.lua was almost as easy as copy-pasting.

--[[
Vector 2D class. Ported to Lua from Keith Peter's AS3 Vector2D
Author : Anggie Bratadinata | www.masputih.com
--]]

Vector2D = {}
Vector2D.__index = Vector2D

-- constructor
function Vector2D.new(initX,initY)
	local instance = {
		x = initX,
		y = initY
	}
	setmetatable(instance,Vector2D)
	return instance
end

--[[
	BASIC MATH OPS
--]]

function Vector2D:dotProduct(v2)
	return self.x * v2.x + self.y * v2.y
end

function Vector2D:angleFrom(v2)

	local v1 = self
	
	if self:isNormalized() == true 
	then
		v1 = self:clone()
		v1:normalize()
	end
	
	if v2:isNormalized() == true
	then
		v2 = v2:clone()
		v2:normalize()
	end
	
	return math.acos(v1:dotProd(v2))
	
end

function Vector2D:add(v2)
	self.x = self.x + v2.x
	self.y = self.y + v2.y
end

function Vector2D:subtract(v2)
	self.x = self.x - v2.x
	self.y = self.y - v2.y
end

function Vector2D:multiply(value)
	self.x = self.x * value
	self.y = self.y * value
end

function Vector2D:divide(value)
	self.x = self.x / value
	self.y = self.y / value
end

--[[
	LENGTH
--]]
function Vector2D:setLength(value)
	local a = self:getAngle()
	self.x = math.cos(a) * value
	self.y = math.sin(a) * value
end

function Vector2D:getLength()
	return math.sqrt(self:getSquareLength())
end

function Vector2D:getSquareLength()
	return self.x * self.x + self.y * self.y
end

-- normalization
function Vector2D:normalize()
	if self:getLength() == 0
	then
		self.x = 1
		self.y = 0
	else
		local l = self:getLength()
		self.x = self.x/l
		self.y = self.y/l
	end
	return self
end

function Vector2D:isNormalized()
	return self:getLength() == 1
end

--[[
	ANGLE
--]]
function Vector2D:getAngle()
	return math.atan2(self.y,self.x)
end

function Vector2D:setAngle(value)
	local l = self:getLength()
	self.x = math.cos(value) * l
	self.y = math.sin(value) * l
end

--[[
	DISTANCE
--]]

-- get the distance of the given vector from this vector
function Vector2D:getDistanceOf(v2)
	return math.sqrt(self:getSquareDistance(v2))
end

function Vector2D:getSquareDistance(v2)
	local dx = v2.x - self.x
	local dy = v2.y - self.y
	return dx * dx + dy * dy
end

--[[
	UTILITIES
--]]

-- determine if the given vector is to the right (+1) or to the left (-1)
-- of this vector
function Vector2D:getSignOf(v2)
	local perp = self:getPerpendicular()
	if perp:dotProduct(v2) < 0
	then
		return -1
	else
		return 1
	end
end

-- return a new vector that is perpendicular to this vector
function Vector2D:getPerpendicular()
	return Vector2D.new(-self.y,self.x)
end


function Vector2D:truncate(maxLength)
	self:setLength(math.min(maxLength,self:getLength()))
end

function Vector2D:zero()
	self.x = 0
	self.y = 0
end

function Vector2D:isZero()
	if self.x == 0 and self.y == 0
	then
		return true
	else
		return false
	end
	
end

function Vector2D:equals(v2)
	return self.x == v2.x and self.y == v2.y
end

function Vector2D:clone()
	return Vector2D.new(self.x,self.y)
end

function Vector2D:toString()
	print("Vector2D[",self.x,",",self.y,"]");
end

-- so that this class can be imported by "geom.Vector2D"
return Vector2D

Continue reading Learning Gideros (and Lua) : Porting Advanced AS3 Animations code

Easy Inheritance & Modularity in Lua

Seeing many flash developers praising Lua-based SDKs like Corona and Gideros that allow us to create mobile games quickly, I couldn’t help trying them myself.

First thing I did was read up some Lua tutorials. The language seems pretty easy to grasp — everything is a table which looks like associative array or a Dictionary in AS3. Good. Until I got to the point where I want to apply/emulate OOP or write code in modular fashion. This is where things become confusing because code examples from Corona and Gideros show you how to shove everything in one big main.lua file. To add even more confusion, different Lua OOP examples show you how to emulate OOP in different ways. And there are things called metatable and metamethods.

After an hour reading the docs and wiki and doing some experiments. I found that it’s really not that hard. Here’s an example of inheritance in one big file.

Continue reading Easy Inheritance & Modularity in Lua