public static ObjModel Parse(string path)
{
string objName = "unnamed";
List <Vector3> vertices = new List <Vector3>();
List <Vector2> uvs = new List <Vector2>();
List <Vector3> normals = new List <Vector3>();
// the faces are lists of triplets of position, normal, uvs
List <List <(int pos, int normal, int uv)> > faces = new List <List <(int pos, int normal, int uv)> >();
// split the obj file into separate lines, since every line is a separate piece of data
string[] lines = File.ReadAllLines(path);
int numLines = lines.Length;
for (int i = 0; i < numLines; i++)
{
var line = lines[i];
// split each line into space-separated tokens
string[] tokens = line.Split(' ');
// the first token defines what the data is supposed to read
switch (tokens[0])
{
case "o":
if (tokens.Length != 2)
{
Console.WriteLine($"Unexpected number of tokens on line {i}");
}
// TODO: do something with like. separate objects
objName = tokens[1];
break;
// position
case "v":
if (tokens.Length != 4)
{
Console.WriteLine($"Unexpected number of tokens on line {i}");
}
// read out the x y z positions from the tokens
float vx, vy, vz;
if (
float.TryParse(tokens[1], out vx) &&
float.TryParse(tokens[2], out vy) &&
float.TryParse(tokens[3], out vz)
)
{
vertices.Add(new Vector3(vx, vy, vz));
}
else
{
Console.WriteLine($"Failed to parse vertex: {line}");
}
break;
// uv
case "vt":
if (tokens.Length != 3)
{
Console.WriteLine($"Unexpected number of tokens on line {i}");
}
float vtx, vty;
if (
float.TryParse(tokens[1], out vtx) &&
float.TryParse(tokens[2], out vty)
)
{
uvs.Add(new Vector2(vtx, 1.0f - vty));
}
else
{
Console.WriteLine($"Failed to parse uv: {line}");
}
break;
// normal
case "vn":
if (tokens.Length != 4)
{
Console.WriteLine($"Unexpected number of tokens on line {i}");
}
float vnx, vny, vnz;
if (
float.TryParse(tokens[1], out vnx) &&
float.TryParse(tokens[2], out vny) &&
float.TryParse(tokens[3], out vnz)
)
{
normals.Add(new Vector3(vnx, vny, vnz));
}
else
{
Console.WriteLine($"Failed to parse normal: {line}");
}
break;
// face
case "f":
if (tokens.Length < 4)
{
Console.WriteLine($"Unexpected number of tokens on line {i}");
}
List <(int, int, int)> faceVerts = new List <(int, int, int)>();
for (int j = 1; j < tokens.Length; j++)
{
// our tokens now look like "5/63/2", so split on the slashes. (it could also be just "5" or "5/63")
var vert = tokens[j].Split('/');
bool failed = false;
int vertVert;
int vertUV = -1;
int vertNormal = -1;
// this ugly tree is a) checking *if* it contains normals and uvs, and b) making sure the format is correct
if (int.TryParse(vert[0], out vertVert))
{
if (vert.Length > 1)
{
if (int.TryParse(vert[1], out vertUV))
{
if (vert.Length > 2)
{
if (int.TryParse(vert[2], out vertNormal))
{
}
else
{
failed = true;
}
}
}
else
{
failed = true;
}
}
}
else
{
failed = true;
}
// do the error checking now
if (failed)
{
Console.WriteLine($"Failed to parse : {tokens[j]}");
break;
}
// indices are 1-indexed in obj format, so we subtract one.
// oops, just noticed i'm not actually handling the case for when it only provides position, or just position and uv etc
faceVerts.Add(((vertVert - 1), (vertNormal - 1), (vertUV - 1)));
}
// add our new list of vertex/normal/uv to the list
faces.Add(faceVerts);
break;
// i don't use any of these tokens, but they are expected to come up
case "mtllib":
case "usemtl":
case "s":
case "g":
case "#":
case "l":
case "":
case " ":
// expected nothing
break;
// if any *other* tokens show up, something is wrong!
default:
// unexpected
Console.WriteLine($"Unexpected token in obj parse. File: {path} Line: {i} Token: {tokens[0]}");
break;
}
}
// ObjVertex is just a container for all three of Position, Normal and UV
List <ObjVertex> objVertices = new List <ObjVertex>();
// this is our output list of triangle indices
List <uint> indices = new List <uint>();
foreach (var f in faces)
{
// this is where i only look for the first 3 verts in a face, since i only care about triangles
// i make sure to triangulate my models before exporting.
for (int i = 0; i < 3; i++)
{
bool found = false;
uint index = 0;
Vector3 position = vertices[f[i].pos];
Vector3 normal = normals[f[i].normal];
Vector2 uv = uvs[f[i].uv];
// create a new ObjVertex from each face, by looking up the indices
ObjVertex objVertex = new ObjVertex()
{
position = position,
normal = normal,
uv = uv
};
// take a look to see if this one already exists
// this is optional! you could just not care about duplicated as long as your meshes aren't super huge
for (int o = 0; o < objVertices.Count; o++)
{
if (objVertices[o].Equals(objVertex))
{
index = (uint)o;
found = true;
break;
}
}
// if its unique (or you skip the previous step), store the new ObjVertex
if (!found)
{
index = (uint)objVertices.Count;
objVertices.Add(objVertex);
}
// add it's index to the new list of triangle indices
indices.Add(index);
}
}
// now just replace the lists with the ObjVertices list
vertices.Clear();
uvs.Clear();
normals.Clear();
for (int i = 0; i < objVertices.Count; i++)
{
vertices.Add(objVertices[i].position);
uvs.Add(objVertices[i].uv);
normals.Add(objVertices[i].normal);
}
// convert to VBOs for opengl to play with
var output = new ObjModel()
{
vertices = new VBO <Vector3>(vertices.ToArray()),
triangles = new VBO <uint>(indices.ToArray(), BufferTarget.ElementArrayBuffer),
normals = new VBO <Vector3>(normals.ToArray()),
uvs = new VBO <Vector2>(uvs.ToArray()),
name = objName
};
output.hash = output.GetHashCode();
return(output);
}
public bool Equals(ObjVertex other)
{
return(position == other.position && normal == other.normal && uv == other.uv);
}
