loader.lua

function load_obj_file(file_path)
  local triangles = {}
  local lines_iterator
  if love then
    lines_iterator = love.filesystem.lines(file_path)
  else
    lines_iterator = io.lines(file_path)
  end
  local index_vertex = {}
  local index_vertex_normal = {}
  for line in lines_iterator do
    local type = line:match "(%S+) .+"
    if type == "v" then
      -- vertex
      local x, y, z = line:match "v (%S+) (%S+) (%S+)"
      local vertex = { x = tonumber(x), y = tonumber(y), z = tonumber(z) }
      table.insert(index_vertex, vertex)
    elseif type == "vn" then
      -- vertex normal
      local x, y, z = line:match "vn (%S+) (%S+) (%S+)"
      local vertex_normal = { x = tonumber(x), y = tonumber(y), z = tonumber(z) }
      table.insert(index_vertex_normal, vertex_normal)
    elseif type == "f" then
      -- face (it's specific for triangulated-mesh: exactly 3 vertices)
      local v1, vn1, v2, vn2, v3, vn3 = line:match "f (%d+)//(%d+) (%d+)//(%d+) (%d+)//(%d+)"
      local triangle = { index_vertex[tonumber(v1)],
        index_vertex[tonumber(v2)], index_vertex[tonumber(v3)] }
      -- do vertex copy (no "shared vertex" problems with setting different "normals", collision)
      --[[bugfix. no shared vertices causing over-writing of normals. simple way, so no need to rewrite other parts of the program.]]
      ---[[
      local function vertex_copy(vertex)
        return { x = vertex.x, y = vertex.y, z = vertex.z }
      end
      triangle = { vertex_copy(triangle[1]), vertex_copy(triangle[2]), vertex_copy(triangle[3]), }
      --]]
      -- normals
      triangle[1].normal = index_vertex_normal[tonumber(vn1)]
      triangle[2].normal = index_vertex_normal[tonumber(vn2)]
      triangle[3].normal = index_vertex_normal[tonumber(vn3)]
      table.insert(triangles, triangle)
    end
  end
  return triangles
end

function load_obj_file_2(file_path)
  local triangles = {}
  local lines_iterator
  if love then
    lines_iterator = love.filesystem.lines(file_path)
  else
    lines_iterator = io.lines(file_path)
  end
  local indexable_vertex_position_xyz = {}
  local indexable_vertex_normal_xyz = {}
  for line in lines_iterator do
    local type = line:match "(%S+) .+"
    if type == "v" then
      -- vertex
      local x, y, z = line:match "v (%S+) (%S+) (%S+)"
      local vertex_position_xyz = { tonumber(x), tonumber(y), tonumber(z) }
      table.insert(indexable_vertex_position_xyz, vertex_position_xyz)
    elseif type == "vn" then
      -- vertex normal
      local x, y, z = line:match "vn (%S+) (%S+) (%S+)"
      local vertex_normal_xyz = { tonumber(x), tonumber(y), tonumber(z) }
      table.insert(indexable_vertex_normal_xyz, vertex_normal_xyz)
    elseif type == "f" then
      -- face (it's specific for triangulated-mesh: exactly 3 vertices)
      local v1, vn1, v2, vn2, v3, vn3 = line:match "f (%d+)//(%d+) (%d+)//(%d+) (%d+)//(%d+)"
      local triangle = {}
      triangle.vertex_position_indices = { tonumber(v1), tonumber(v2), tonumber(v3) }
      triangle.vertex_normal_indices = { tonumber(vn1), tonumber(vn2), tonumber(vn3) }
      table.insert(triangles, triangle)
    end
  end
  return { triangles, indexable_vertex_position_xyz, indexable_vertex_normal_xyz }
end