Submitted by MGA on

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*' turtle essence.bas SmallBASIC 0.12.9 (B+=MGA) 2017-06-13*

*' From my experience with Draw Strings and Nano series, *

*' I think I have discovered the essence of Turtle Drawing*

*' I contend that all can be done with 5 global variables*

*' x, y the start position of ray = ra line*

*' a, r the radian angle of direction to go and r the distance*

*' p is pen color, draw if 0 <= p <= 15 (QB colors 0 - 15)*

*' and one graphics command ra (as sub or gosub)*

sub ra

local x1 = x + r * cos(a)

local y1 = y + r * sin(a)

*' if pen p has a color draw, else just update x, y position*

if 0 <= p and p <= 15 then line x, y, x1, y1, p

x = x1 : y = y1 *'update x, y with current turtle position*

end

*'===== that's all the setup you need to do turle drawing*

*'but let's setup a Home position in middle of screen*

homeX = xmax/2 : homeY = ymax/2

*' lines commented out are from Galileo's tree code found at*

*' http://retrogamecoding.org/board/index.php?topic=581.0*

*'this code modifies Galileo's allowing tree to grow and sway with beautiful background!*

*'import turtle3*

*'clear screen*

*'startTurtle()*

*'home() ' oh this sets start angle at 270 degrees or 3*pi/2*

x = homex: y =homey

a = 3*pi/2

*'goy(200)*

y = y + 200

*'pen(1)*

*'color 0, 255, 0*

p = 6

horizon = ymax/2 + 100

for i = 1 to 300

cls

for h= 0 to horizon

midInk 0,0,128, 40, 200, 255, h/horizon

line 0, h, xmax, h

next

for h = horizon to ymax

midInk 40,200,255, 50, 200, 50, (h-horizon)/(ymax-horizon)

line 0, h, xmax, h

next

tree i

showpage

next

while 1

sway = sway + (rnd*2) -1

if sway > 25 then sway = 25

if sway < -25 then sway = -25

cls

for h= 0 to horizon

midInk 0,0,128, 40, 200, 255, h/horizon

line 0, h, xmax, h

next

for h = horizon to ymax

midInk 40,200,255, 50, 200, 50, (h-horizon)/(ymax-horizon)

line 0, h, xmax, h

next

a = a + rad(sway)

tree i

a = a - rad(sway)

showpage

wend

pause

sub tree(size)

if size < 5 then

*'move(size)*

r = size

ra

*'move(-size)*

r = -size

ra

*'return*

exit sub

end if

*'move(size/3)*

r = size/3

ra

*'turn(-30)*

a = a - rad(30 + sway)

tree(size*2/3)

*'turn(30)*

a = a + rad(30 + sway)

*'move(size/6)*

r = size/6

ra

*'turn(25)*

a = a + rad(25 + sway)

tree(size/2)

*'turn(-25)*

a = a - rad(25 + sway)

*'move(size/3)*

r = size/3

ra

*'turn(25)*

a = a + rad(25 + sway)

tree(size/2)

*'turn(-25)*

a = a - rad(25 + sway)

*'move(size/6)*

r = size/6

ra

*'move(-size)*

r = -size

ra

end sub

sub midInk(r1, g1, b1, r2, g2, b2, fr)

color rgb(r1+(r2-r1)*fr, g1+(g2-g1)*fr, b1+(b2-b1)*fr)

end

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johnno56 replied on Permalink

## Cool. That's one nasty breeze

Cool. That's one nasty breeze you've got going there. I let it run for a while and it bent quite a bit. I thought it was going to "snap off" at one point... lol

Nicely done.

J

figosdev replied on Permalink

## mga has transformed, from a

mga has transformed, from a coder to a person that thinks about how languages work, and implements them.

i thought this might happen. its a wonderful thing. i wish i could take all the credit, but actually he had already written the draw strings program when i really started pushing him (and that draw strings program was enough.)

MGA replied on Permalink

## Oh more trees!