Serpinsky Triangle with recursion

[BenLi]

Hey,
this is my first attempt at recursion, probably going to make a fractal tree next

code:

setscreen ("graphics:800;600") %serpinsky var middlex, middley:int %var x1,y1,x2,y2,x3,y3:int fcn midx (x1, x2:int):int middlex:= (((x2 - x1)div 2)+ x1) result middlex end midx fcn midy (y1, y2:int):int middley:= (((y2 - y1)div 2)+ y1) result middley end midy proc serpinsky (x1, y1, x2, y2, x3, y3:int) drawline (x1, y1, x2, y2, black) drawline (x2, y2, x3, y3, black) drawline (x1, y1, x3, y3, black) drawline (midx (x1, x2), midy ( y1, y2), midx (x1, x3), midy ( y1, y3), black) drawline (midx (x1, x2), midy ( y1, y2), midx (x2, x3), midy ( y2, y3), black) drawline (midx (x1, x3), midy ( y1, y3), midx (x2, x3), midy ( y2, y3), black) serpinsky (midx (x1, x2), midy ( y1, y2),midx (x1, x3), midy ( y1, y3),midx (x2, x3), midy ( y2, y3)) end serpinsky serpinsky (0, 0, 400, 600, maxx, 0)

actually, its not actually a serpinsky yet...

[zylum]

suggestion: make sure you have a terminating condition for your recursion. if you let your program run long enough, it eats up all the memory and crashes.

also, like you mentioned, its not quite a serpinsky triangle. an easy way to make a serpinsky triangle is to draw your beginning triangle, then half way between its centre and each of its vertices, draw another one half its size.

code:

setscreen ("graphics:600;600") proc triangle (cx, cy, s : real, d : int)     if d = 0 then         return     end if     var x, y : array 1 .. 3 of int     for i : 1 .. 3         x (i) := round (cosd (i * 120 - 30) * s + cx)         y (i) := round (sind (i * 120 - 30) * s + cy)         triangle (cosd (i * 120 - 30) * (s / 2) + cx, sind (i * 120 - 30) * (s / 2) + cy, s / 2, d - 1)     end for     drawpolygon (x, y, 3, black)     delay (10) end triangle triangle (maxx div 2, maxy div 3, 340, 7)

good luck with your fractal tree and recursion there are a few good source codes for fractal trees. also take a look at my recursion tutorial in turing tutorials

[MysticVegeta]

zylum, I haven't taken grade 11 trig yet, can you guide me over what is happening in the draw polygon? I understand the recursion but I dont understand how you come up with values for the x and y array, I know they represent the vertices of the triangle, but dont know whats going on in them, lol

[HellblazerX]

First of all, drawpolygon takes in an array of coordinates to draw the polygon. A triangle has three points, so he puts in an array of 3 x coordinates and an array of 3 y coordinates to draw the triangle. To get the x and y coordinates, he just takes the trigonometric values of them in the unit circle, and mulitplying by the size of the triangle. This way he can resize the triangles very easily.

[zylum]

what ^he^ said

[MysticVegeta]

HellblazerX wrote:

First of all, drawpolygon takes in an array of coordinates to draw the polygon. A triangle has three points, so he puts in an array of 3 x coordinates and an array of 3 y coordinates to draw the triangle. To get the x and y coordinates, he just takes the trigonometric values of them in the unit circle, and mulitplying by the size of the triangle. This way he can resize the triangles very easily.

yeah I know that but I asked, how to "come up" withthe x and y vals, just the trig part I have a hard time understanding...