OBJ Loader

package cjminecraft.engine.loaders;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.joml.Vector2f;
import org.joml.Vector3f;

import cjminecraft.engine.Engine;
import cjminecraft.engine.util.Vertex;
import cjminecraft.engine.util.objects.RawObject;

public class OBJLoader {

	public static RawObject loadOBJ(String fileName) {
		fileName = Engine.getOption("models.location") + "/" + fileName + ".obj";
		FileReader fr = null;
		File objFile = new File(fileName);
		try {
			fr = new FileReader(objFile);
		} catch (FileNotFoundException e) {
			System.err.println("File not found: " + fileName);
			System.exit(-1);
		}
		BufferedReader reader = new BufferedReader(fr);
		String line;
		List<Vertex> vertices = new ArrayList<Vertex>();
		List<Vector2f> textures = new ArrayList<Vector2f>();
		List<Vector3f> normals = new ArrayList<Vector3f>();
		List<Integer> indices = new ArrayList<Integer>();
		try {
			while (true) {
				line = reader.readLine();
				if (line.startsWith("v ")) {
					String[] currentLine = line.split(" ");
					Vector3f vertex = new Vector3f(Float.parseFloat(currentLine[1]), Float.parseFloat(currentLine[2]),
							Float.parseFloat(currentLine[3]));
					Vertex newVertex = new Vertex(vertices.size(), vertex);
					vertices.add(newVertex);
				} else if (line.startsWith("vt ")) {
					String[] currentLine = line.split(" ");
					Vector2f texture = new Vector2f(Float.parseFloat(currentLine[1]), Float.parseFloat(currentLine[2]));
					textures.add(texture);
				} else if (line.startsWith("vn ")) {
					String[] currentLine = line.split(" ");
					Vector3f normal = new Vector3f(Float.parseFloat(currentLine[1]), Float.parseFloat(currentLine[2]),
							Float.valueOf(currentLine[3]));
					normals.add(normal);
				} else if (line.startsWith("f ")) {
					break;
				}
			}
			while (line != null && line.startsWith("f ")) {
				String[] currentLine = line.split(" ");
				String[] vertex1 = currentLine[1].split("/");
				String[] vertex2 = currentLine[2].split("/");
				String[] vertex3 = currentLine[3].split("/");
				Vertex v0 = processVertex(vertex1, vertices, indices);
				Vertex v1 = processVertex(vertex2, vertices, indices);
				Vertex v2 = processVertex(vertex3, vertices, indices);
				calculateTangents(v0, v1, v2, textures);
				line = reader.readLine();
			}
			reader.close();
		} catch (IOException e) {
			System.err.println("Error reading file: " + fileName);
			System.exit(-1);
		}
		removeUnusedVertices(vertices);
		float[] verticesArray = new float[vertices.size() * 3];
		float[] texturesArray = new float[vertices.size() * 2];
		float[] normalsArray = new float[vertices.size() * 3];
		float[] tangentsArray = new float[vertices.size() * 3];
		int[] indicesArray = convertIndicesListToArray(indices);
		return VaoLoader.loadToVAO(verticesArray, texturesArray, normalsArray, tangentsArray, indicesArray);
	}

	private static void calculateTangents(Vertex v0, Vertex v1, Vertex v2, List<Vector2f> textures) {
		Vector3f delatPos1 = v1.getPosition().sub(v0.getPosition());
		Vector3f delatPos2 = v2.getPosition().sub(v0.getPosition());
		Vector2f uv0 = textures.get(v0.getTextureIndex());
		Vector2f uv1 = textures.get(v1.getTextureIndex());
		Vector2f uv2 = textures.get(v2.getTextureIndex());
		Vector2f deltaUv1 = uv1.sub(uv0);
		Vector2f deltaUv2 = uv2.sub(uv0);

		float r = 1.0f / (deltaUv1.x * deltaUv2.y - deltaUv1.y * deltaUv2.x);
		delatPos1.mul(deltaUv2.y);
		delatPos2.mul(deltaUv1.y);
		Vector3f tangent = delatPos1.sub(delatPos2);
		tangent.mul(r);
		v0.addTangent(tangent);
		v1.addTangent(tangent);
		v2.addTangent(tangent);
	}

	private static Vertex processVertex(String[] vertex, List<Vertex> vertices, List<Integer> indices) {
		int index = Integer.parseInt(vertex[0]) - 1;
		Vertex currentVertex = vertices.get(index);
		int textureIndex = Integer.parseInt(vertex[1]) - 1;
		int normalIndex = Integer.parseInt(vertex[2]) - 1;
		if (!currentVertex.isSet()) {
			currentVertex.setTextureIndex(textureIndex);
			currentVertex.setNormalIndex(normalIndex);
			indices.add(index);
			return currentVertex;
		} else {
			return dealWithAlreadyProcessedVertex(currentVertex, textureIndex, normalIndex, indices, vertices);
		}
	}

	private static int[] convertIndicesListToArray(List<Integer> indices) {
		int[] indicesArray = new int[indices.size()];
		for (int i = 0; i < indicesArray.length; i++) {
			indicesArray[i] = indices.get(i);
		}
		return indicesArray;
	}

	private static Vertex dealWithAlreadyProcessedVertex(Vertex previousVertex, int newTextureIndex, int newNormalIndex,
			List<Integer> indices, List<Vertex> vertices) {
		if (previousVertex.hasSameTextureAndNormal(newTextureIndex, newNormalIndex)) {
			indices.add(previousVertex.getIndex());
			return previousVertex;
		} else {
			Vertex anotherVertex = previousVertex.getDuplicateVertex();
			if (anotherVertex != null) {
				return dealWithAlreadyProcessedVertex(anotherVertex, newTextureIndex, newNormalIndex, indices,
						vertices);
			} else {
				Vertex duplicateVertex = new Vertex(vertices.size(), previousVertex.getPosition());
				duplicateVertex.setTextureIndex(newTextureIndex);
				duplicateVertex.setNormalIndex(newNormalIndex);
				previousVertex.setDuplicateVertex(duplicateVertex);
				vertices.add(duplicateVertex);
				indices.add(duplicateVertex.getIndex());
				return duplicateVertex;
			}

		}
	}

	private static void removeUnusedVertices(List<Vertex> vertices) {
		for (Vertex vertex : vertices) {
			vertex.averageTangents();
			if (!vertex.isSet()) {
				vertex.setTextureIndex(0);
				vertex.setNormalIndex(0);
			}
		}
	}

}