122

+local component = require("component")
+local event = require("event")
+local keyboard = require("keyboard")
+local shell = require("shell")
+local term = require("term")
+local unicode = require("unicode")
+local raytracer = require("raytracer")
+
+local args = shell.parse(...)
+if #args < 1 then
+  io.write("Usage: print3d-view FILE [fov]\n")
+  os.exit(0)
+end
+
+-- model loading
+
+local file, reason = io.open(args[1], "r")
+if not file then
+  io.stderr:write("Failed opening file: " .. reason .. "\n")
+  os.exit(1)
+end
+
+local rawdata = file:read("*all")
+file:close()
+local data, reason = load("return " .. rawdata)
+if not data then
+  io.stderr:write("Failed loading model: " .. reason .. "\n")
+  os.exit(2)
+end
+data = data()
+
+-- set up raytracer
+
+local rt = raytracer.new()
+rt.camera.position={-22+8,20+8,-22+8}
+rt.camera.target={8,8,8}
+rt.camera.fov=tonumber(args[2]) or 90
+
+local state
+local function setState(value)
+  if state ~= value then
+    state = value
+    rt.model = {}
+    for _, shape in ipairs(data.shapes or {}) do
+      if not not shape.state == state then
+        table.insert(rt.model, shape)
+      end
+    end
+    if state and #rt.model < 1 then -- no shapes for active state
+      setState(false)
+    end
+  end
+end
+setState(false)
+
+-- set up gpu
+
+local gpu = component.gpu
+local cfg, cbg
+local function setForeground(color)
+  if cfg ~= color then
+    gpu.setForeground(color)
+    cfg = color
+  end
+end
+local function setBackground(color)
+  if cbg ~= color then
+    gpu.setBackground(color)
+    cbg = color
+  end
+end
+
+-- helper functions
+
+local function vrotate(v, origin, angle)
+  local x, y = v[1]-origin[1], v[3]-origin[3]
+  local s = math.sin(angle)
+  local c = math.cos(angle)
+
+  local rotx = x * c + y * s
+  local roty = -x * s + y * c
+  return {rotx+origin[1], v[2], roty+origin[3]}
+end
+
+local function ambient(normal)
+  if math.abs(normal[1]) > 0.5 then
+    return 0.6
+  elseif math.abs(normal[3]) > 0.5 then
+    return 0.8
+  elseif normal[2] > 0 then
+    return 1.0
+  else
+    return 0.4
+  end
+end
+
+local function hash(str)
+  local result = 7
+  for i=1,#str do
+    result = (result*31 + string.byte(str, i))%0xFFFFFFFF
+  end
+  return result
+end
+
+local function multiply(color, brightness)
+  local r,b,g=(color/2^16)%256,(color/2^8)%256,color%256
+  r = r*brightness
+  g = g*brightness
+  b = b*brightness
+  return r*2^16+g*2^8+b
+end
+
+local palette = {0x0000FF, 0x00FF00, 0x00FFFF, 0xFF0000, 0xFF00FF, 0xFFFF00, 0xFFFFFF}
+
+-- render model
+while true do
+  setForeground(0x000000)
+  setBackground(0x000000)
+  local rx, ry = gpu.getResolution()
+  gpu.fill(1, 1, rx, ry, unicode.char(0x2580))
+
+  rt:render(rx, ry*2, function(x, y, shape, normal)
+    local sx, sy = x, math.ceil(y / 2)
+    local ch, fg, bg = gpu.get(sx, sy)
+    local brightness = ambient(normal)
+    local color = multiply(data.palette and data.palette[shape.texture] or palette[hash(shape.texture or "") % #palette + 1], brightness)
+    if color == 0x000000 then return end
+    if y % 2 == 1 then
+      setBackground(bg)
+      setForeground(color)
+    else
+      setBackground(color)
+      setForeground(fg)
+    end
+    gpu.set(sx, sy, ch)
+  end)
+
+  gpu.setForeground(0xFFFFFF)
+  gpu.setBackground(0x000000)
+
+  gpu.set(1, ry, "[q] Quit    [left/right] Rotate    [space] Toggle state")
+  os.sleep(0.1) -- consume events that arrived in the meantime
+  while true do
+    local _,_,_,code=event.pull("key_down")
+    if code == keyboard.keys.q then
+      term.clear()
+      os.exit(0)
+    elseif code == keyboard.keys.space then
+      setState(not state)
+      break
+    elseif code == keyboard.keys.left then
+      local step = 10
+      if keyboard.isShiftDown() then step = 90 end
+      rt.camera.position = vrotate(rt.camera.position, rt.camera.target, -step/180*math.pi)
+      break
+    elseif code == keyboard.keys.right then
+      local step = 10
+      if keyboard.isShiftDown() then step = 90 end
+      rt.camera.position = vrotate(rt.camera.position, rt.camera.target, step/180*math.pi)
+      break
+    end
+  end
+end