Tweetjam 3D Donut

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Tweetjam 3D Donut

by 2darray

Cart #50802 | 2018-03-25 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA

12

It's a frosted 3D donut, drawn in 265 chars of Lua!

I'm including the code here, with spacing and indents for legibility (instead of minimizing chars like in the cart).

Variable meanings:
X/Y/Z: Current sample position (moves along a camera ray), +Y is up
I/J: Screenspace position
U/V/W: Ray direction (normalized)
C: Output color of the current ray
K: Raymarch iterator
Q: Distance to the unextruded torus on XZ plane
L: Shortest distance to the surface of the extruded 3D torus
A: Angular position of sample pos around the torus (0-1, repeating)

(Both distance values are signed: a negative distance means that a point is inside a shape)

cls(2)
::_::
x=0
y=2
z=-3
i=rnd(112)+8
j=rnd(66)+40
u=i/128-.5
v=-(j/128)
w=sqrt(1-u*u-v*v)
c=2
for k=1,20 do
	q=sqrt(x*x+z*z)-1
	l=sqrt(q*q+y*y)-.5
	if (z>4 or y<-1) then
		break
	end
	if (l<.08) then
		a=t()/64+atan2(z,x)
		c=(-y*5-.3+sin(a*6)/4)
		break
	end
	x+=u*l
	y+=v*l
	z+=w*l
end
pset(i,j,max(c%16,1))
goto _

Wow! I'm fiddling around with it right now, and it's quite interesting. I should be learning from you!