LÖVE

Code: Select all

function drawObject(object)
	love.graphics.push()
	love.graphics.translate(...)
	love.graphics.rotate(...)
	love.graphics.scale(...)
	
	-- I want to do something like this:
	globalPos, globalRot, globalScale = love.graphics.currentTransformation() 
	
	for k, v in pairs(object.children) do
		drawObject(v)
	end	
	love.graphics.pop()
end

Code: Select all

local lgorigin = love.graphics.origin
local lgscale = love.graphics.scale
local lgrotate = love.graphics.rotate
local lgshear = love.graphics.shear
local lgtranslate = love.graphics.translate

-- The implicit third row is always 0, 0, 1
local matrix = {1,0,0,
                0,1,0}

local function getMatrix(t)
  if t == nil then
    -- Return a copy
    return {matrix[ 1], matrix[ 2], matrix[ 3],
            matrix[ 4], matrix[ 5], matrix[ 6]}
  end
  -- Assign the elements (enables reusing tables)
  -- (unrolled loop)
  t[1] = matrix[1]; t[2] = matrix[2]; t[3] = matrix[3]
  t[4] = matrix[4]; t[5] = matrix[5]; t[6] = matrix[6]
  return t
end

local function origin()
  matrix[1] = 1  matrix[2] = 0  matrix[3] = 0
  matrix[4] = 0  matrix[5] = 1  matrix[6] = 0
  lgorigin()
end

local function scale(x, y)
  matrix[1] = matrix[1] * x; matrix[2] = matrix[2] * y
  matrix[4] = matrix[4] * x; matrix[5] = matrix[5] * y
  lgscale(x, y)
end

local function rotate(a)
  local c, s = math.cos(a), math.sin(a)
  matrix[1], matrix[2] = matrix[1]*c + matrix[2]*s, matrix[1]*-s + matrix[2]*c
  matrix[4], matrix[5] = matrix[4]*c + matrix[5]*s, matrix[4]*-s + matrix[5]*c
  lgrotate(a)
end

local function shear(x, y)
  matrix[1], matrix[2] = matrix[1] + matrix[2]*y, matrix[1]*x + matrix[2]
  matrix[4], matrix[5] = matrix[4] + matrix[5]*y, matrix[4]*x + matrix[5]
  lgshear(x, y)
end

local function translate(x, y)
  matrix[3] = matrix[3] + matrix[1]*x + matrix[2]*y
  matrix[6] = matrix[6] + matrix[4]*x + matrix[5]*y
  lgtranslate(x, y)
end

local function xform(matrix, x, y)
  return matrix[1]*x + matrix[2]*y + matrix[3], matrix[4]*x + matrix[5]*y + matrix[6]
end

local function xformBack(matrix, x, y)
  x, y = x - matrix[3], y - matrix[6]
  local det = matrix[1] * matrix[5] - matrix[2] * matrix[4]
  if det ~= 0 then
    return (matrix[5] * x - matrix[2] * y) / det,
           (matrix[1] * y - matrix[4] * x) / det
  end
  -- The transform is 1D or 0D
  return x, y
end

return {getMatrix=getMatrix, xform = xform, xformBack = xformBack, origin=origin,
        scale=scale, rotate=rotate, shear=shear, translate=translate}

Code: Select all

local xform = require('xform')
local matrix

function love.draw()
  xform.origin()
  love.graphics.setColor(255,255,255)
  xform.translate(400,300)
  xform.rotate(0.3)
  xform.scale(0.7, 1.1)
  xform.translate(42, 86)
  xform.rotate(0.5)
  xform.shear(1.7, 1.3)
  matrix = xform.getMatrix()
  love.graphics.rectangle("fill", 5, 9, 53, 31)

  xform.origin()
  love.graphics.setColor(255,0,0)
  local x, y = xform.xform(matrix, 5, 9)
  love.graphics.rectangle("fill", x-1, y-1, 3, 3)
  x, y = xform.xform(matrix, 5+52, 9)
  love.graphics.rectangle("fill", x-1, y-1, 3, 3)
  x, y = xform.xform(matrix, 5, 9+30)
  love.graphics.rectangle("fill", x-1, y-1, 3, 3)
  x, y = xform.xform(matrix, 5+52, 9+30)
  love.graphics.rectangle("fill", x-1, y-1, 3, 3)

  x, y = xform.xformBack(matrix, xform.xform(matrix, 5, 3))
  love.graphics.print(string.format("%.17g\t%.17g\t%s", x, y, "<- should be 5, 3"))
end

Code: Select all

local xform = require 'xform'

do
  local lg = love.graphics
  lg.translate = xform.translate
  lg.rotate = xform.rotate
  lg.scale = xform.scale
  lg.shear = xform.shear
  lg.origin = xform.origin
end