planets.lua

x = 64
y = 64
r = 20

sunz = 10

nmap = {}
cmap = {}

interleave = 1

function dot(v1, v2)
 return (v1.x * v2.x) + (v1.y * v2.y) + (v1.z * v2.z);
end

function printv(v)
 print (v.x .. " " .. v.y .. " " .. v.z)
end

function distance(x, y)
 return sqrt(x*x + y*y)
end

function length(v)
 return sqrt(v.x*v.x + v.y*v.y + v.z*v.z)
end

function normalize(v)
 l = length(v)
 v.x = v.x/l
 v.y = v.y/l
 v.z = v.z/l
 return v
end

function mouse_normalized()
 v={}
 v.x = mouse_x / 128
 v.y = mouse_y / 128
 v.z = 10
 return v
end

mouse_x = 0
mouse_y = 0

function _init()
  poke(0x5f2d, 1) -- for the mouse

  nullv = {}
  nullv.x = 0
  nullv.y = 0
  nullv.z = 0

  -- initializes the normal and clip map
  for i=0,128,1 do
   nmap[i] = {}
   cmap[i] = {}
   for j=0,128,1 do
    nmap[i][j] = nullv
    cmap[i][j] = false
   end
  end
end

sunv={}

function _update()
 -- controls
 if btn(0) then r=r+1 end
 if btn(1) then r=r-1 end
 if btn(2) then sunz=sunz+1 end
 if btn(3) then sunz=sunz-1 end
 if btn(4) then interleave = interleave + 1 end
 if btn(5) and interleave > 1 then interleave = interleave - 1 end
end

-- clears the clipmap
function clc()
  for i=0,128,1 do
   for j=0,128,1 do
    cmap[i][j] = false
   end
  end
end

function _draw()
 cls()

 clc() -- clears the clipmap

 mouse_x = stat(32)
 mouse_y = stat(33)

 normm = mouse_normalized()

 -- sun light vector
 sunv.x = (normm.x - 0.5) * 10
 sunv.y = (normm.y - 0.5) * 10
 sunv.z = sunz

 sunv = normalize(sunv)

 -- orbiting planet 1
 t = time()
 op1x = 64 + sin(t * 0.1) * 40
 op1y = 64 + cos(t * 0.1) * 15

 op2x = 64 + sin(t * 0.02) * 80
 op2y = 64 + cos(t * 0.02) * 30

 -- planet
 sphere(x,y,r)
 -- dip
 --sphere(64, 64, 8, true)

 sphere(op1x,op1y,3,1)
 sphere(op2x,op2y,5,1)

 render()

 pset(mouse_x,mouse_y,9)
end

function sphere(x,y,r,inv)
 x = flr(x)
 y = flr(y)

 --rectfill(x-r,y-r,r*2,r*2,0)
 --circfill(x,y,r,1)

 srand(1)

 xs = x-r
 ys = y-r
 xf = xs+r*2
 yf = ys+r*2

 for yi=ys,yf,1 do
  for xi=xs,xf,1 do
   --if (pget(xi,yi) == 2) then
    if xi > 0 and xi < 128 and 
       yi > 0 and yi < 128 and
       yi % interleave == 0
       then

     normal={}
     normal.x = (xi-x) / r-- + rnd(0.3)
     normal.y = (yi-y) / r-- + rnd(0.3)
     dist = distance(normal.x, normal.y)
 
     if (dist < 1) then
      cmap[xi][yi] = true
  
      
      
      normal.z = sqrt(1 - dist*dist) --1-distance(normal.x, normal.y)
  
      --c = dot(normal, sunv)
      if inv == true then
       normal.x = -normal.x
       normal.y = -normal.y
       --normal.z = -normal.z
      end
  
  
      if xi == mouse_x and yi == mouse_y then
       printv(normal)
       --print(c)
      end
  
      nmap[xi][yi] = normal
 
     end
    end
    -- pset(xi,yi,mapc(c))
   --end
  end 
 end  

end

function render()
 cls()
 for xi=0,128,1 do
  for yi=0,128,interleave do
   n = nmap[xi][yi]
   if cmap[xi][yi] == true then
    -- lambert lighting:
    c = dot(n, sunv)
    -- set color:
    pset(xi,yi,mapc(c))
   end
  end
 end
end

-- maps value to color
function mapc (c)
 if c > 0.9 then
  c = 7 
  elseif c > 0.5 then
  c = 9 
  elseif c > 0 then
  c = 4 
  else c = 0
  end
 return c
end

--main()