Hi all,
Here’s a first draft rev of the Mandelbrot explorer I coded up yesterday based on a few of your sample code projects. Tapping the screen will zoom the image in around your tap point. You can change a few global parameters to ramp up the resolution at the expense of longer update intervals, and select between a few simple rendering options. You’ll notice that I went a little wild fiddling with variable localization and memory access vs. calculation performance tests. Consider this rev pre-release. I haven’t yet begun to explore issues around closure optimization or loop format testing.
All this has raised a few interesting oddities and questions for me, a Lua novice.
1.) Printing the ElapsedTime return value seems to give odd numbers that don’t make sense when successive calls are bracketed around the rendering and calculation loops. Can anyone explain the proper print format or why there is no interval shown bracketing a long loop that clearly takes several seconds to compute?
2.) When you tap the screen to zoom in, there is a multi-second pause before the touch is registered, longer than the draw rendering delay accounts for. What might be going on here that takes so much time? Garbage collection? Any suggestions on how to manage this?
3.) I noticed that the draw rendering interval increases slowly. Very slowly, but it seems to increase pretty monotomically just repeating the draw cycle. Memory leak? Closures? Any idea what gives?
A few things on my to-do list, but suggestions are welcome here from anyone with more than the remote Lua clue I cling to.
- solve the ElapsedTime oddities.
- fiddle with performance tweaks and learn how Lua performance issues differ from, say, c++.
- add a zoom-out gesture, either two finger, pinch, or double-tap
- add some more rendering options, including perhaps a smooth escape radius algorithm.
Finally, a challenge for you Lua hotshots. How fast can you make it go? Any optimization suggestions or tweaks? Help a Lua novice brother out!
Source:
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--Mandelbrot set image explorer by Phillip Alvelda
RMode= "Color"
tileNumber = 150
tileSize = WIDTH/tileNumber
tilesize= tileSize
MinRe = -2.0
MaxRe = 2
MinIm = -2.0
MaxIm = 2
Re_factor = (MaxRe-MinRe)/(WIDTH -1)
Im_factor = (MaxIm-MinIm)/(HEIGHT -1)
MaxIterations = 255
UCounter =0
count=0
red={}
green={}
blue ={}
tiles = {}
for y= 1,HEIGHT/tilesize do
tiles[y] = {}
end
-- Use this function to perform your initial setup
function setup()
setInstructionLimit(0)
InitColorMap()
ManSetCalc()
end
function InitColorMap()
for i=0,MaxIterations do
if RMode == "Iterations" then
red[i]=255-i*255/MaxIterations
green[i]=255-i*255/MaxIterations
blue[i]=255-i*255/MaxIterations
elseif RMode == "Color" then
red[i]=(i*8) % 255
green[i] = (i*9) % 255
blue[i] = (i * 4) % 255
elseif RMode == "Binary" then
if (value % 2) == 0 then
red[i]=255
green[i]=255
blue[i]=255
else
red[i]=0
green[i]=0
blue[i]=0
end
end
end
end
function touched(touch)
if touch.state == ENDED then --only use the final touch event to scale image window
dre=MaxRe-MinRe
dim=MaxIm-MinIm
x = MinRe + touch.x/WIDTH * dre
y = MinIm + touch.y/HEIGHT * dim
print ("touch x=",x,"y=",y)
--set the zoom factor and new window borders
MinRe = x - dre / 3
MaxRe = x + dre / 3
MinIm = y - dim / 3
MaxIm = y + dim / 3
Re_factor = (MaxRe-MinRe)/(WIDTH -1)
Im_factor = (MaxIm-MinIm)/(HEIGHT -1)
print "Zoom in, Regen..."
ManSetCalc()
print "Done."
end
end
function ManSetCalc()
print("Calc Start",ElapsedTime )
local y, x, n, isInside
local ylim=HEIGHT/tilesize
local xlim=WIDTH/tilesize
local ltiles=tiles
local imf=Im_factor*tilesize
local ref=Re_factor*tilesize
local iterations
for y = 1, ylim do
c_im = MinIm + y*imf
for x = 1, xlim do
c_re = MinRe + x*ref
Z_re = c_re
Z_im = c_im
isInside = true
for n=0, MaxIterations, 1 do
Z_re2 = Z_re*Z_re
Z_im2 = Z_im*Z_im
iterations=n
if(Z_re2 + Z_im2 > 4)then
isInside = false
break
end
Z_im = 2*Z_re*Z_im + c_im
Z_re = Z_re2 - Z_im2 + c_re
end
ltiles[y][x] = iterations
end
end
print("End",ElapsedTime)
end
function draw()
print("Draw interval=",DeltaTime)
count = count + 1
noSmooth()
background(0, 0, 0, 255)
scale(tilesize,tilesize)
local lred=red
local lgreen=green
local lblue=blue
local ltiles=tiles
local x,y,column, value
local lrect=rect
local lfill=fill
local lipairs=ipairs
for y,column in lipairs(ltiles) do
for x,value in lipairs(column) do
lfill(lred[value],lgreen[value],lblue[value],255)
--fill((value*8) % 255, (value*9) % 255,(value*4) % 255,255)
lrect(x, y, 1, 1)
end
end
end
