add obj loader

data/scripts/classes/obj.lua

@@ -0,0 +1,125 @@
+---@class Obj
+---@field model string
+---@field texture string
+---@field texture_size integer
+---@field position Vector3
+---@field triangles table
+local Obj = {}
+
+local Vector3 = require "types.vector3"
+
+Obj.__index = Obj
+
+local function string_split(str, delimiter)
+  local res = {}
+  local i = 0
+  local f
+  local match = '(.-)' .. delimiter .. '()'
+  
+  if string.find(str, delimiter) == nil then
+    return {str}
+  end
+  
+  for sub, j in string.gmatch(str, match) do
+    i = i + 1
+    res[i] = sub
+    f = j
+  end
+  
+  if i ~= 0 then
+    res[i+1] = string.sub(str, f)
+  end
+  
+  return res
+end
+
+---parses the obj file and triangulates it for drawing
+---@param model string path to obj model
+---@param texture {file: string, size: number}
+---@param position Vector3?
+---@return Obj
+function Obj.create(model, texture, position)
+  local pos
+  if position ~= nil then
+    pos = position
+  else
+    pos = Vector3()
+  end
+  local obj = {
+    model = model,
+    texture = texture.file,
+    texture_size = texture.size,
+    position = pos:copy(),
+
+    triangles = {}
+  }
+  obj.position = obj.position:copy()
+  setmetatable(obj, Obj)
+  -- adapted from https://github.com/karai17/lua-obj/blob/master/obj_loader.lua
+  -- Copyright (c) 2014 Landon Manning - LManning17@gmail.com - LandonManning.com
+  -- MIT
+  local file = file_read{file = obj.model}
+  local lines = string_split(file, "\r?\n")
+  local obj_data = {
+    v = {},
+    vt = {},
+    f = {},
+  }
+  for _, line in ipairs(lines) do
+    local l = string_split(line, "%s+")
+    if l[1] == "v" then
+      local v = {
+        x = tonumber(l[2]),
+        y = tonumber(l[3]),
+        z = tonumber(l[4]),
+      }
+      table.insert(obj_data.v, v)
+    elseif l[1] == "vt" then
+      local vt = {
+        x = tonumber(l[2]) * obj.texture_size,
+        y = tonumber(l[3]) * obj.texture_size,
+      }
+      table.insert(obj_data.vt, vt)
+    elseif l[1] == "f" then
+      local f = {}
+      for i = 2, #l do
+        local split = string_split(l[i], "/")
+        local v = {}
+
+        v.v = tonumber(split[1])
+        if split[2] ~= "" then v.vt = tonumber(split[2]) end
+        -- v.vn = tonumber(split[3])
+
+        table.insert(f, v)
+      end
+      table.insert(obj_data.f, f)
+    end
+  end
+  for _, face in ipairs(obj_data.f) do
+    for i = 2, #face - 1 do
+      local triangle = {
+        v0 = obj_data.v[face[1].v],
+        v1 = obj_data.v[face[i].v],
+        v2 = obj_data.v[face[i + 1].v],
+        uv0 = obj_data.vt[face[1].vt],
+        uv1 = obj_data.vt[face[i].vt],
+        uv2 = obj_data.vt[face[i + 1].vt],
+        texture = obj.texture
+      }
+      table.insert(obj.triangles, triangle)
+    end
+  end
+  return obj
+end
+
+function Obj:draw()
+  for _, triangle in ipairs(self.triangles) do
+    local newt = util.shallow_copy(triangle)
+    newt.v0 = Vector3(triangle.v0) + self.position
+    newt.v1 = Vector3(triangle.v1) + self.position
+    newt.v2 = Vector3(triangle.v2) + self.position
+    draw_triangle(newt)
+  end
+end
+
+return Obj