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 ðŸ™‚ 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

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