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Re: Balls! Pt 4

by teamster_jr (Curate)
on Jun 14, 2006 at 10:25 UTC ( #555206=note: print w/ replies, xml ) Need Help??


in reply to Balls! Pt 4

commented and cleaned up code is in the spoiler:

#!/usr/bin/perl open f, ">o.bmp"; # print the bmp file header, and the colour pallette # (3 entries : 0=black, 1 = blue, 2 = dark blue); print f pack "a2V9x20C2x2C1016", BM, 18318, 0, 1078, 40, 140, 130, 524 +289, 0, 18200, 168, 0, 98; # make a string of null bytes for the image; $image = pack "x18200"; # PIE! $pi = 4 * atan2( 1, 1 ); # rotate around the origin 0 to 2000 degrees # (*10 so we do it in increments of .1 degrees) for $angle ( 0 .. 20000 ) { # convert to radians and change it to .1 degrees # (1 rad = degrees * pi / 180) $radians = $angle * $pi / 1800; map { # polar equation of a logarithmic spiral ($radius=exp($angle)); # the /9 is shorter than /10 :) and makes it a tighter spiral # $_ holds the offset within this map - which gives the spiral a width # (thinking about it i could have just added it to the radius) $radius = exp( ( $radians + $_ / 9 ) / 9 ) / 9; # this is the reiman projection (project from a plane through a sphere # to its north pole - mark where it meets the sphere) # also the conversion to cartesian coords $x = ( 1 / ( $radius + 1 / $radius ) ) * cos $radians; $y = ( 1 / ( $radius + 1 / $radius ) ) * sin $radians; # this sets the pixel in the image vec( $image, # and this works out the offset for the correct byte to set # (offset=$x+$width(140) *$y) int( # this is the new $x - using an isometric conversion: # ($x'= $x+$y - rotate through 45 degrees) 70 * ( 1 + $x + $y ) + # this is new $y - ($y'=$z+($y-$x)/2 (squish it) 140 * ( 10 + int( 15 + 80 * # the height at which the projection meets the sphere ($z) $radius**2 / ( 1 + $radius**2 ) + 40 * ( $y - $x ) ) ) ), 8 ) # and this changes the colour based on the angle of our rotation = ( $pi / 2 + $radians ) % ( 2 * $pi ) > $pi ? 2 : 1 # /map to give width } 0 .. 15 } # print the image print f $image


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