private static (List <Vertex> vertices, List <VertexNormal> normals, List <TextureUv> uvs, List <Group> groups) ExtractOBJData(string[] lines)
{
var enumerable = from line in lines
let split = line.Split(' ', StringSplitOptions.RemoveEmptyEntries).Select(l => l.Trim()).ToArray()
where split.Any() && !split.First().StartsWith("#")
select split;
var vertices = new List <Vertex>();
var normals = new List <VertexNormal>();
var uvs = new List <TextureUv>();
var currentGroup = new Group("unnamed");
var groups = new List <Group>();
var elementComparer = new ElementComparer(vertices, uvs, normals);
foreach (var line in enumerable)
{
switch (line[0])
{
case "v":
Debug.Assert(line.Length == 4);
var vertex = new Vertex
{
X = float.Parse(line[1]),
Y = float.Parse(line[2]),
Z = float.Parse(line[3])
};
vertices.Add(vertex);
break;
case "vn":
Debug.Assert(line.Length == 4);
normals.Add(new VertexNormal
{
X = float.Parse(line[1]),
Y = float.Parse(line[2]),
Z = float.Parse(line[3])
});
break;
case "vt":
uvs.Add(new TextureUv
{
U = float.Parse(line[1]),
V = float.Parse(line[2])
//Ignore w
});
break;
case "g":
case "o": //For the sake of bedrock, treat groups and objects as the same thing.
currentGroup = new Group(line[1]);
groups.Add(currentGroup);
break;
case "f":
Debug.Assert(line.Length >= 4 && line.Length <= 5);
var polygon = new Polygon();
for (var i = 1; i < line.Length; ++i)
{
var elements = line[i].Split("/");
var vertexIndex = int.Parse(elements[0]);
var textureUvIndex = int.Parse(elements[1]);
if (elements.Length > 2)
{
var normalIndex = int.Parse(elements[2]);
polygon.AddElement(new Element(vertexIndex, textureUvIndex, normalIndex));
}
else
{
polygon.AddElement(new Element(vertexIndex, textureUvIndex));
}
}
if (currentGroup.TryGetPreviousPolygon(out var lastPolygon) && lastPolygon.Vertices.Count == 3)
{
var uniqueElements = lastPolygon.Vertices.Except(polygon.Vertices, elementComparer).ToArray();
var missingElements = polygon.Vertices.Except(lastPolygon.Vertices, elementComparer).ToArray();
if (uniqueElements.Length == 1 && missingElements.Length == 1)
{
lastPolygon.RepairToQuad(missingElements.Single());
}
else
{
currentGroup.AddPolygon(polygon);
}
}
else
{
currentGroup.AddPolygon(polygon);
}
break;
}
}