Initial

g3d/objloader.lua

@@ -0,0 +1,84 @@
+-- written by groverbuger for g3d
+-- september 2021
+-- MIT license
+
+----------------------------------------------------------------------------------------------------
+-- simple obj loader
+----------------------------------------------------------------------------------------------------
+local inspect = require "inspect"
+
+-- give path of file
+-- returns a lua table representation
+return function (path, flipU, flipV)
+    local positions, faces, uvs, normals, model = {}, {}, {}, {}, {}
+
+    -- go line by line through the file
+    for line in love.filesystem.lines(path) do
+        local words = {}
+
+        -- split the line into words
+        for word in line:gmatch "([^%s]+)" do
+            table.insert(words, word)
+        end
+
+        local firstWord = words[1]
+
+        if firstWord == "v" then
+            -- if the first word in this line is a "v", then this defines a vertex's position
+
+            table.insert(positions, {tonumber(words[2]), tonumber(words[3]), tonumber(words[4])})
+			--print(table.concat(positions[#positions],";"))
+        elseif firstWord == "vt" then
+            -- if the first word in this line is a "vt", then this defines a texture coordinate
+			
+			-- Blender 2.9+ V axis points UP, whereas LÖVE's Y axis points DOWN
+			-- Not sure if any other software has U axis inverted, but why not add this just in case?
+			local U, V = tonumber(words[2]), tonumber(words[3])			
+			if flipU then U = 1 - U end
+			if flipV then V = 1 - V end
+			
+            table.insert(uvs, {U,V})
+        elseif firstWord == "vn" then
+            -- if the first word in this line is a "vn", then this defines a vertex normal
+
+            table.insert(normals, {tonumber(words[2]), tonumber(words[3]), tonumber(words[4])})
+        elseif firstWord == "f" then
+            -- if the first word in this line is a "f", then this is a face
+            -- a face takes three point definitions
+            -- the arguments a point definition takes are vertex, vertex texture, vertex normal in that order
+
+            assert(#words == 4, ("Faces in %s must be triangulated before they can be used in g3d!"):format(path))
+            local face = {v = {}, vt = {}, n = {}}
+
+			
+            for i=2, #words do			    
+                local v, vt, n = words[i]:match "(%d+)/(%d+)/(%d+)"				
+				--print(v,vt,n)
+				if not (v and vt and n) then
+				   v, vt = words[i]:match "(%d+)/(%d+)"
+				   n = 1
+				end
+                table.insert(face.v,  tonumber(v))
+                table.insert(face.vt, tonumber(vt))
+                table.insert(face.n,  tonumber(n))
+				
+            end
+            table.insert(faces, face)
+			
+        end
+    end
+
+    -- put it all together in the right order
+    for _, face in pairs(faces) do
+        for i=1, 3 do
+            local vert = {unpack(positions[face.v[i]])}
+            for _, uv in ipairs(uvs[face.vt[i]]) do table.insert(vert, uv) end
+			if (normals[face.n[i]]) then
+               for _, normal in ipairs(normals[face.n[i]]) do table.insert(vert, normal) end
+			end
+            table.insert(model, vert)
+        end
+    end
+
+    return model
+end