pico-8 cartridge // http://www.pico-8.com
version 18
__lua__
-- three dee!
-- by @johanpeitz

-- next up
-- camera movement
-- camera rotation

function _init()
 tick=0

 scene={}

 cam={
  x=0,
  y=1,
  z=2,
  pitch=0,
  yaw=0,
  roll=0,
  troll=0
 }

 add(scene,make_plane())

 cube=make_cube()
 cube.scale=0.5
 cube.y=-0.25
 add(scene,cube)

 cube=make_cube()
 cube.scale=0.25
 cube.y=-0.625
 cube.ecol=10
 add(scene,cube)

 cube=make_cube()
 cube.scale=0.5
 cube.y=-1
 cube.ecol=8
 add(scene,cube)

end


function make_plane()
 local p={
  x = 0,
  y = 0,
  z = 0,
  pitch = 0,
  yaw = 0,
  roll = 0,
  scale = 1,
  ecol = 7,
  ncol = 6
 }
 p.nodes={
  { -0.5, 0, -0.5},
  {  0.5, 0, -0.5},
  {  0.5, 0,  0.5},
  { -0.5, 0,  0.5},
 }
 p.edges={
  {1,2},
  {2,3},
  {3,4},
  {4,1},
  {3,1},
  {2,4},
 }

 return p
end

function make_cube()
 local c={
  x = 0,
  y = 0,
  z = 0,
  pitch = 0,
  yaw = 0,
  roll = 0,
  scale = 1,
  ecol = 11,
  ncol = 3
 }

 c.nodes={
  { -0.5, -0.5, -0.5},
  { -0.5, -0.5,  0.5},
  { -0.5,  0.5, -0.5},
  { -0.5,  0.5,  0.5},
  {  0.5, -0.5, -0.5},
  {  0.5, -0.5,  0.5},
  {  0.5,  0.5, -0.5},
  {  0.5,  0.5,  0.5},
 }

 c.edges={
  {1,2},
  {2,4},
  {4,3},
  {3,1},
  {5,6},
  {6,8},
  {8,7},
  {7,5},
  {1,5},
  {2,6},
  {3,7},
  {4,8},
 }

 return c
end


function _update()
 if (btn(❎)) cube.yaw+=0.02

 if (btn(⬆️)) cam.z-=0.05
 if (btn(⬇️)) cam.z+=0.05

 if btn(⬅️) then
  cam.x+=0.05
  cam.troll=0.05
 elseif btn(➡️) then
  cam.x-=0.05
  cam.troll=-0.05
 else
  cam.troll=0
 end

 cam.roll+=0.1*(cam.troll-cam.roll)

end


function _draw()
 tick+=1

 cls()

 for m in all(scene) do
  to_cam(m)
  to_scrn(m)
  draw_model(m)
 end

 print("∧"..flr(stat(1)*100).."%",0,0,3)
end
-->8
-- 3d stuff

function to_cam(m)
 pitch = m.pitch + cam.pitch
 roll  = m.roll  + cam.roll
 yaw   = m.yaw   + cam.yaw

 local cosa = cos(roll)
 local sina = sin(roll)
 local cosb = cos(yaw)
 local sinb = sin(yaw)
 local cosc = cos(pitch)
 local sinc = sin(pitch)

 local axx = cosa*cosb
 local axy = cosa*sinb*sinc - sina*cosc
 local axz = cosa*sinb*cosc + sina*sinc

 local ayx = sina*cosb
 local ayy = sina*sinb*sinc + cosa*cosc
 local ayz = sina*sinb*cosc - cosa*sinc

 local azx = -sinb
 local azy = cosb*sinc
 local azz = cosb*cosc

 for n in all(m.nodes) do
  local px=n[1]
  local py=n[2]
  local pz=n[3]
  n.cx = cam.x + m.x + m.scale*(axx*px + axy*py + axz*pz)
  n.cy = cam.y + m.y + m.scale*(ayx*px + ayy*py + ayz*pz)
  n.cz = cam.z + m.z + m.scale*(azx*px + azy*py + azz*pz)
 end

end


function to_scrn(m)
 for n in all(m.nodes) do
  n.sx=64+n.cx*64/n.cz
  n.sy=64+n.cy*64/n.cz
 end
end


function draw_model(m)
 for e in all(m.edges) do
  local n1=m.nodes[e[1]]
  local n2=m.nodes[e[2]]

  if n1.cz>0.01 and n2.cz>0.01 then
   line(n1.sx,n1.sy,
        n2.sx,n2.sy,m.ecol)

   --pset(n1.sx,n1.sy,m.ncol)
   --pset(n2.sx,n2.sy,m.ncol)
  end

 end
end