## GLE Example: recursiontree.gle

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size 8 8 ! Based on "C" code by Lode Vandevenne ! http://www.student.kuleuven.ac.be/~m0216922/CG/ set cap round maxRecursions = 8 ! never make this too big or it'll take forever angle = 0.2 * pi ! angle in radians shrink = 1.8 ! relative size of new branches ! Now follows the recursion function, a function that only draws a single line and calls ! itself a few times, but results in a huge tree! sub recursion posX posY dirX dirY bsize n ! Here's the part that draws the line. The line is drawn from (posX, posY) to (posX+dirX, ! posY+dirY). So the position and direction of the line is given as a vector, instead of ! a begin point, an angle and a size, because direction vectors are much easier to work ! with. The size parameter itself isn't used to draw the line directly, it's only needed ! later to calculate the direction vector of the next branches. If the maximum number of ! recursions is reached, the function returns immediately after drawing the line, without ! calling itself again. local posX2 = posX + bsize * dirX local posY2 = posY + bsize * dirY if n > 5 then set color forestgreen else set color rgb255(128, 96, 64) end if set lwidth 0.2/(n+1)+0.005 amove posX pageheight()-posY aline posX2 pageheight()-posY2 if n < maxRecursions then ! And in the second part of the function, the new position of the new branches is ! calculated as the endpoint of the previous branch, and the new direction vector for ! the new branches is calculated out of the size and current direction of the current ! branch. The new branches are rotated with the angle, the sine and cosine formulas are ! actually the calculation of the rotation matrix. Then the recursion function is called ! again with the new branch as its parameters. This is done twice: once for a branch ! rotated to the right, and then for a branch rotated to the left. dirX2 = cos(angle) * dirX + sin(angle) * dirY dirY2 = -sin(angle) * dirX + cos(angle) * dirY recursion posX2 posY2 dirX2 dirY2 bsize/shrink n+1 dirX2 = cos(-angle) * dirX + sin(-angle) * dirY dirY2 = -sin(-angle) * dirX + cos(-angle) * dirY recursion posX2 posY2 dirX2 dirY2 bsize/shrink n+1 end if end sub ! The main program doesn't do much more than calling the recursive function. ! The value "h/2.3" in the parameters of the recursion function is the initial ! length of the first branch (the stem). The coordinates are the begin ! point and direction vector of the first branch. w = pagewidth() h = pageheight() recursion w/2 h-0.1 0 -1 h/2.3 0

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