Hypocycloid Program (included)
lazarus / 39-Graphics

----------------------------------------------------------------------
speter · 2020-12-20 06:09

G'Day Folks,

I was looking through some old code and came across a (Turbo Pascal)
program I wrote to draw Hypocycloid patterns.

I have ported it to Laz - which was a very simple task; it uses
Pixels[] so it is fairly slow; but that is part of its charm. The
pattern builds up over time; changing as it goes.

Anyway, the project it attached to this post.

I find the patterns amazing and hypnotic. Enjoy. 

Note that it will NOT work in macOS. I couldn't get it to work using
the OnPaint method to draw the pattern.

cheers
S.

----------------------------------------------------------------------
wp · 2020-12-20 11:51

Nice.

When you draw into a bitmap, paint that bitmap on the Paintbox canvas
in the Paintbox OnPaint handler and call Paintbox.Invalidate after
setting a (or several) pixel then the program works also on Mac. This
way the "art pattern" is persistent regarding repaint requests by the
OS: While your program is calculating drag the form halfway out of the
screen and then back - see what happens...

I am attaching a modified version according to this suggestion. I also
allows to close the form by clicking the "x" button while the
calculation is running.

----------------------------------------------------------------------
jwdietrich · 2020-12-20 19:26

Thanks. With @wp's modification, it works charmingly on the Mac, too.

----------------------------------------------------------------------
speter · 2020-12-20 22:55

Thanks wp.

cheers
S.

----------------------------------------------------------------------
speter · 2020-12-21 01:24

G'Day Folks,

Here is a new version of my hypocycloid pattern drawing program; based
on wp's tweak of my first version.

  v1.2
    + the program now draws on a bitmap, this will hopefully work with
macOS.
    + handles resize
    + key / mouse click now "toggles" drawing
    + allows user to set the background colour.

Enjoy.

cheers
S.

----------------------------------------------------------------------
trev · 2020-12-21 08:28

Quote from: speter on December 21, 2020, 02:24:24 amHere is a new
version of my hypocycloid pattern drawing program; based on wp's tweak
of my first version.

  v1.2
Works perfectly, albeit slowly, on macOS

----------------------------------------------------------------------
wp · 2020-12-21 10:25

Regarding the speed you could pick up your old idea again of doing
several cycles of calculation before a repaint is performed:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure T
Form1.Process;//------------------------------------------------------
--------------const  inc_a : single = pi/50;  GROUP_SIZE = 10;var 
start_colour : tcolor;  ratio, a, b, h, penpos, ang_a, ang_b, inc_b :
single;  mid : tpoint;  i, x, y : integer;begin  // Draw background 
bmp.Canvas.Brush.Color := Shape_bg.brush.color; 
bmp.Canvas.FillRect(0, 0, bmp.Width, bmp.Height);   // Start
parameters  mid := point(bmp.width div 2, bmp.height div 2);  ratio :=
1 + random*10;  penpos := 1 + random*10;  start_colour := random(1 shl
25);  a := 0.5 * ratio * bmp.height / (ratio + penpos -1);  b := a /
ratio;  inc_b := (a-b)/b;  h := penpos * b;  ang_a := 0;   // Create
hypocycloid pixel by pixel  repeat    for i := 1 to GROUP_SIZE do   
begin      ang_a += inc_a;      ang_b := ang_a * inc_b;      x :=
trunc (mid.x + (a-b)*cos(ang_a) + h*cos(ang_b));      y := trunc
(mid.y - (a-b)*sin(ang_a) + h*sin(ang_b));       if
bmp.Canvas.Pixels[x, y] <> Shape_bg.brush.color then       
bmp.Canvas.Pixels[x, y] := random(1 shl 25)      else       
bmp.Canvas.Pixels[x, y] := start_colour;    end;    
Paintbox1.Invalidate;    Application.ProcessMessages;  until
finished;end;
Additionally, making the constant GROUP_SIZE a user-defined variable
would allow the user to adjust the drawing speed himself. Of course it
must be guaranteed that the variable is not less than 1 (this would
not calculate anything) or too large (this would not update the
display at all or at too large intervals; find out the limit yourself.

----------------------------------------------------------------------
speter · 2020-12-24 00:31

Thanks wp, good idea.

I've changed the program, re-introducing the inner loop. I've added an
edit-box to allow the user to set the loop size (constrained to
1..200).

cheers
S.

----------------------------------------------------------------------
speter · 2024-03-19 04:33

I've recently been relooking at pixel drawing code.
In another thread  WP included an example using LazIntfImage.

So, here (finally) is my hypocycloid rewritten using (much) faster
graphics.

If you'd like some nice (sugar free) donuts, checkout the attached
project.

cheers
S.

----------------------------------------------------------------------
Dzandaa · 2024-03-19 14:09

Hi,

I adapted speter code to TBGRABitmap.

Have fun, great forum.

B->

----------------------------------------------------------------------
Thaddy · 2024-03-19 18:02

too much donuts... have fun you both....