canvas_setpixel (mandelbrot)

**largo_winch** · 25-10-2011, 14:40

hello. I wanted to explore some UI/Canvas functions and started this mandelbrot-looks-like example. the problem zones I have marked. perhaps anybody can check this code example. the aim of this example I show as image

my results shows only a black creating pixel canvas window, but that's not ok.

use at own risk.

' Empty GUI script created on 10-25-2011 12:48:25 by largo_winch (ThinAIR)

Uses "console", "ui"

Randomize Timer

Function TBMain () As Long
    Local hwin As DWord
    Local tmr, xmin, xmax, ymin, ymax, cx, cy, dcx, dcy, x, y, zr, zi As Single
    Local xi, j,k, numiter, numxpix, numypix, te, ts As Long
    Local color_map(216) As Long
    Local stuff_done As Long
    Local s As String  
 
    hWin = Canvas_Window ("Canvas_colors_testing - kind of mandelbrot", 50, 50,  800, 600)     
        
    Canvas_Attach hwin, 0, Redraw
    Canvas_Scale Pixels
           
    xmin = -.65 : xmax = -.45 : ymin = .52 : ymax = .72 : numiter = 215
    numxpix = 800 
    numypix = 600 
    dcx = (xmax - xmin)/(numxpix - 1)
    dcy = (ymin - ymax)/(numypix - 1)
    
    '-----------------------> 1 --------------------------->
    ReDim color_map (216) '(6*6*6) 
    For xi = 1 To 5
        For j = 1 To 5
            For k = 1 To 5
                color_map(xi + 6*j + 36*k) = Rgb(51*j,51*xi,51*k)                
            Next
        Next
    Next
    ts = Timer
    tmr = Timer
    cx = xmin
    
    '-----------------------> 2 --------------------------->      
    ReDim color_map(216)
    For xi = 1 To numxpix
        cy = ymax
        For j = 1 To numypix
            x = cx
            y = cy
            For k = 1 To numiter
               zr = x*x - y*y + cx 
                zi = 2*x*y + cy                                
                '-----------> important ------------->
                If (zr*zr + zi*zi) > 4 Then 'Exit                 
                x = zr : y = zi
                End If
            Next           
            cy += dcy                                                          
            '-------------------> problem zone 2 --------------------------------->
            Canvas_SetPixel(xi, j, color_map(numiter+2-k) )
            
            'Canvas_SetPixel(xi, j, color_map(numiter + 1 - k)) ' +1 doesn't work, out of range!            
            'Canvas_SetPixel(xi, j, color_map(numiter+2-k) ) '-> result black painting!            
            'Canvas_SetPixel(x, y, Rgb(color_map(numiter+1), color_map(numiter+1), color_map(numiter+1))) ' testing ok
            'Canvas_SetPixel(x, y, Rgb(0, 255, 0)) ' testing ok
            '-------------------> problem zone 2 --------------------------------->                        
        Next        
        cx += dcx 
    Next                         
        
    Canvas_Color(Rgb(255,10,10))
    Canvas_SetPos(20,420)  
    s = Format$(("Took ##.## seconds ") + Format$(Timer - tmr) )
    'Format$(w)+"x"+Format$(h)+","+Str$(Len(s))+" bytes total"
    Canvas_Print s  
      MsgBox 0, "testing ok?"
      
    Canvas_Redraw
    te = Timer
    Canvas_WaitKey(27)    
  
  Canvas_Window End
 
End Function

bye, largo

**ErosOlmi** · 25-10-2011, 17:13

I am by car and I'm posting from iPhone so I cannot test but looking at data I just realize inner loop is 800x600x215=103200000 loops and it can take a while to show results for an interpreted programming language like thinbasic

I will check better when home

**largo_winch** · 25-10-2011, 18:04

I am back at home too

thanks eros. I am very close to solve the problem zone.

'-----------> that's the important thingy !------------->                
                If (zr*zr + zi*zi) > 4 Then Exit                 
                x = zr : y = zi                                
                'End If                                                                
                '-----------> that's the important thingy !------------->

how I can convert

If (zr*zr + zi*zi) > 4 Then Exit

to thinbasic? "Then Exit" thinbasic doesn't like.

error message: error code 37:

EXIT: exit from a non supported block

then everything will be fine. The black pixel window is ok after my further testings

I've tested with lower resolution

numxpix = 400 '800 
    numypix = 300 '600

bye largo and thanks for fast feedback

**ErosOlmi** · 25-10-2011, 18:12

Here again from car an iPhone

(quite complex but not impossible)

In thinbasic EXIT must be followed by the name of the construct you want to exit.
So: exit for, exit while, Exit function, ...
See help at http://www.thinbasic.com/public/prod....html?exit.htm

Ciao
Eros

**largo_winch** · 25-10-2011, 19:28

now I am very close to the solution. thanks for the hint with loop/exit eros! There will be some more tests, but perhaps the problem caused a) by missing loops, I am astonished and b) canvas_setpixel formula. I have used "do.. loop.. exit for" for my new example.

use again at own risk!

' Empty GUI script created on 10-25-2011 12:48:25 by largo_winch (ThinAIR)

Uses "console", "ui"

Randomize Timer

Function TBMain () As Long
    Local hwin As DWord
    Local tmr, xmin, xmax, ymin, ymax, cx, cy, dcx, dcy, x, y, zr, zi As Single
    Local xi, j,k, numiter, numxpix, numypix, te, ts As Long
    Local color_map(216) As Long
    Local stuff_done As Long
    Local s As String  
                                                                                 '800,600
    hWin = Canvas_Window ("Canvas_colors_testing - kind of mandelbrot", 50, 50,  400, 300)     
        
    Canvas_Attach hwin, 0, Redraw
    Canvas_Scale Pixels
           
    xmin = -.65 : xmax = -.45 : ymin = .52 : ymax = .72 : numiter = 215
    numxpix = 400 '800 
    numypix = 300 '600 
    dcx = (xmax - xmin)/(numxpix - 1)
    dcy = (ymin - ymax)/(numypix - 1)

Do  
   '-----------------------> 1 --------------------------->
    ReDim color_map(216) '(6*6*6) 216
    For xi = 1 To 5
        For j = 1 To 5
            For k = 1 To 5
                color_map(xi + 6*j + 36*k) = Rgb(51*j,51*xi,51*k)                                                
            Next
        Next
    Next
    ts  = Timer
    tmr = Timer
    cx  = xmin
    
    '-----------------------> 2 --------------------------->      
    ReDim color_map(216) 

    For xi = 1 To numxpix
        cy = ymax
        For j = 1 To numypix
            x = cx
            y = cy            
            For k = 1 To numiter
               zr = x*x - y*y + cx 
                zi = 2*x*y + cy                                                

                '-----------> that's the important thingy !------------->                                
                If (zr*zr + zi*zi) > 4 Then Exit For 'Do 'Exit 
                x = zr : y = zi                                
     '           Console_WriteLine "FOR/NEXT zr=" + Format$(zr)
     '           Console_WriteLine "FOR/NEXT zi=" + Format$(zi)                
     
                '-----------> that's the important thingy !------------->                
            Next           
            cy += dcy                                                            
            '-------------------> problem zone nearly solved! --------------------------------->                        
            Canvas_SetPixel(xi, j, Rgb(numiter+2-k, 255*zi, 255*zr)) ' testing ok
            '-------------------> problem zone  --------------------------------->                        
        Next        
        cx += dcx 
    Next                         
Loop

    Canvas_Color(Rgb(255,10,10))
    Canvas_SetPos(20,420)  
      s = Format$(("Took ##.## seconds ") + Format$(Timer - tmr) )
    Canvas_Print s  
      MsgBox 0, "testing ok?" ' example works
          
    Canvas_Redraw
    te = Timer
    Canvas_WaitKey(27)    
  
  Canvas_Window End
 
End Function

here's the problem zone for clearing better performance

 Canvas_SetPixel(xi, j, Rgb(numiter+2-k, 255*zi, 255*zr)) ' testing ok

only the chaotic background (not linear) is still a problem I will see to solve it for next time.

pic and tbasic example as attachement.

bye, largo

**ErosOlmi** · 25-10-2011, 19:47

Dear largo,

the do/loop is creating and endless loop because there is no condition to exit from it and (as far as I can understand) looping seems having no meaning for the program. Why doing what you have already done?

Another strange pont is second

ReDim color_map(216)

You have dimensioned and filled color_map() array just few lines above. If you redim it again you are in practice destroying it and allocating another array.

Ciao
Eros

**ErosOlmi** · 25-10-2011, 19:54

Regarding colors, you filled color_map() arra but never used.
Maybe you would like to change

            Canvas_SetPixel(xi, j, Rgb(color_map(numiter+2-k), 255*zi, 216*zr)) ' testing ok

with something like

            Canvas_SetPixel(xi, j, color_map(numiter+2-k) ) ' testing ok

color_map() already contains a RGB color.

Just guessing.

Attached my image after that change
Ciao
Eros

**ErosOlmi** · 25-10-2011, 20:09

Again guessing ...
The last problem may be related to how you fill your color_map() array. Your code

    ReDim color_map(216) '(6*6*6) 216
    For xi = 1 To 5
        For j = 1 To 5
            For k = 1 To 5
                color_map(xi + 6*j + 36*k) = Rgb(51*j,51*xi,51*k)                                                
            Next
        Next
    Next

seems filling 5*5*5 (125) buckets while your array seems to be 6*6*6

Maybe you have to change it with something like that (or something more clever)

    ReDim color_map(216) '(6*6*6) 216
    For xi = 1 To 6
        For j = 1 To 6
            For k = 1 To 6
                color_map(xi + 6*(j-1) + 36*(k-1)) = Rgb(51*j,51*xi,51*k)                                                
            Next
        Next
    Next

See image after this change

**largo_winch** · 25-10-2011, 21:54

thank you eros, you've shown and focussed for me the dilemma I have had! thinbasic doesn't work with 0 to 5 arrays (1 to 6), then I've doubled used rgb values, therefore I've got these hypnotical backgrounds, but if you like some joints or other people I have created an armada of examples last hour you can be sure they are nice little artworks for (digital) exhibitions

my son (8 years old) was coming back at late afternoon from school and noticed my examples and wanted to know what's teacher of his school is able to create such beautiful paintings, so we have had a lot of fun together to do more than 20 examples with chaotical structures for background and madelbrot patterns too. thanks for pointing me in right direction! if you like you can manipulate data for different colors and change window size for bigger one.

1) working examples: (one of hundred possible examples)

' Empty GUI script created on 10-25-2011 12:48:25 by largo_winch (ThinAIR)

Uses "console", "ui"

Randomize Timer

Function TBMain () As Long
    Local hwin As DWord
    Local tmr, xmin, xmax, ymin, ymax, cx, cy, dcx, dcy, x, y, zr, zi As Single
    Local xi, j,k, numiter, numxpix, numypix, te, ts As Long
    Local color_map(216) As Long
    Local stuff_done As Long
    Local s As String  
                                                                              '800,600
    hWin = Canvas_Window ("Canvas_colors_testing 1e_go : mandelbrot", 50, 50, 400, 300)     
        
    Canvas_Attach hwin, 0, Redraw
    Canvas_Scale Pixels
           
    xmin = -.65 : xmax = -.45 : ymin = .52 : ymax = .72 : numiter = 215
    numxpix = 400 '800 
    numypix = 300 '600 
    dcx = (xmax - xmin)/(numxpix - 1)
    dcy = (ymin - ymax)/(numypix - 1)

Do  
   '-----------------------> problem 1 solved array dimension ! --------------------------->
    ReDim color_map(216) '(6*6*6) 216
    For xi = 1 To 6
        For j = 1 To 6
            For k = 1 To 6     'but "6*j + 36*k" doesn't work here (I don't grasp it!)                 
                color_map(xi + 5*j + 30*k) = Rgb(51*j,51*xi,51*k)                                                
            Next
        Next
    Next
    '-----------------------> problem 1 solved array dimension ! --------------------------->
    ts  = Timer
    tmr = Timer
    cx  = xmin    
    '-----------------------> 2 --------------------------->          
    For xi = 1 To numxpix
        cy = ymax
        For j = 1 To numypix
            x = cx
            y = cy            
            For k = 1 To numiter
               zr = x*x - y*y + cx 
                zi = 2*x*y + cy                                                

                '-----------> important thingy solved !-------------> 
                If (zr*zr + zi*zi) > 4 Then Exit For 
                x = zr : y = zi                                
                'Console_WriteLine "FOR/NEXT zr=" + Format$(zr)
                'Console_WriteLine "FOR/NEXT zi=" + Format$(zi)                
                '-----------> important thingy solved !------------->                 
            Next           
            cy += dcy                                                            
            '-------------------> problem zone 2 solved! --------------------------------->                                   
            Canvas_SetPixel(xi, j, color_map(numiter+2-k) ) ' testing ok            
            
            '-------------------> problem zone 2 solved --------------------------------->                        
        Next        
        cx += dcx 
    Next                         
    'Canvas_Clear(color_map(numiter+2-k)) 'starts rendering again ;)
        
    Canvas_Color(Rgb(255,10,10))
    Canvas_SetPos(20,120)  
      s = Format$(("Took ##.## seconds ") + Format$(Timer - tmr) )
    Canvas_Print s  
      'MsgBox 0, "testing ok?" ' example works
          
    Canvas_Redraw
Loop
    te = Timer
    Canvas_WaitKey(27)    

  
  Canvas_Window End
 
End Function

2)
btw:

            For k = 1 To 6     'but "6*j + 36*k" doesn't work here (I don't grasp it!)                 
                color_map(xi + 5*j + 30*k) = Rgb(51*j,51*xi,51*k)

3) don't use console printing (I have deactivated these lines) because it decrease heavy rendering speed. and if you like you can "Canvas_Clear(color_map(numiter+2-k)) 'starts rendering again

" activate so rendering starts again. all in all that was a real funny work! my son is absolutely happy that all works here and will ask next days his friends how to build such structures with their laptops at math. courses.

4) example and pic as attachement

bye, largo

**ErosOlmi** · 25-10-2011, 22:18

Great largo.
I'm happy I could help.

Your example is also very useful for me because I can use it as a stress test when sometime I go into thinBasic optimization phase

Your example is perfect because it involves big loops with some math inside.

Have fun with your son. I can understand you: it is great moment when you can share some time with your son making things that are fun for both of you.

Ciao
Eros

PS: you can get a little speed improvement not using SINGLE data type but using DOUBLE instead. SINGLE data type is always internally truncated to correct SINGLE "imprecision"