public static async Task <WavefrontObject> ReadFromFile(string filename)
{
var builder = new ObjBuilder();
await using var file = File.OpenRead(filename);
await file.ReadToEnd(async line =>
{
if (line.StartsWith("#") || line.Length == 0)
{
return;
}
var splitLine = line.Split(' ', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
if (splitLine.Length < 2)
{
throw new FormatException("Line has the wrong format");
}
if (splitLine[0] == "mtllib")
{
var materialFile = Path.Combine(Path.GetDirectoryName(filename) ?? string.Empty, splitLine[1]);
var materials = await new MaterialParser().ReadFromFile(materialFile);
builder.SetMaterials(materials);
}
else
{
ParseCommand(builder, splitLine);
}
});
return(builder.Build());
}
private static void ParseCommand(ObjBuilder builder, string[] line)
{
var command = line[0];
var values = new ReadOnlySpan <string>(line, 1, line.Length - 1);
switch (command)
{
case "s": builder.AddSmoothGroup(values); break;
case "v": builder.AddPosition(values); break;
case "vt": builder.AddTexture(values); break;
case "vn": builder.AddNormal(values); break;
case "f": builder.AddFace(values); break;
case "g": builder.AddGroup(values); break;
case "usemtl": builder.UseMaterial(values); break;
case "o": break; // Don't care about object right now
case "new": break; // Don't care about new right now
default: Console.WriteLine($"{command} is not recognized as a wavefront obj identifier"); break;
}
}