LiteCraft/src/main/java/io/github/hydos/ginger/engine/obj/OBJFileLoader.java

package io.github.hydos.ginger.engine.obj;

import java.io.*;
import java.util.*;

import org.joml.*;

public class OBJFileLoader
{
	private static final String RES_LOC = "/models/";

	public static ModelData loadOBJ(String objFileName)
	{
		String objFile = RES_LOC + objFileName;
		InputStreamReader isr = new InputStreamReader(OBJFileLoader.class.getResourceAsStream(objFile));
		BufferedReader reader = new BufferedReader(isr);
		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.valueOf(currentLine[1]),
						Float.valueOf(currentLine[2]),
						Float.valueOf(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.valueOf(currentLine[1]),
						Float.valueOf(currentLine[2]));
					textures.add(texture);
				}
				else if (line.startsWith("vn "))
				{
					String[] currentLine = line.split(" ");
					Vector3f normal = new Vector3f(Float.valueOf(currentLine[1]),
						Float.valueOf(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("/");
				processVertex(vertex1, vertices, indices);
				processVertex(vertex2, vertices, indices);
				processVertex(vertex3, vertices, indices);
				line = reader.readLine();
			}
			reader.close();
		}
		catch (IOException e)
		{
			System.err.println("Error reading the file");
		}
		removeUnusedVertices(vertices);
		float[] verticesArray = new float[vertices.size() * 3];
		float[] texturesArray = new float[vertices.size() * 2];
		float[] normalsArray = new float[vertices.size() * 3];
		float furthest = convertDataToArrays(vertices, textures, normals, verticesArray,
			texturesArray, normalsArray);
		int[] indicesArray = convertIndicesListToArray(indices);
		ModelData data = new ModelData(verticesArray, texturesArray, normalsArray, indicesArray,
			furthest);
		return data;
	}

	private static void 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);
		}
		else
		{
			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 float convertDataToArrays(List<Vertex> vertices, List<Vector2f> textures,
		List<Vector3f> normals, float[] verticesArray, float[] texturesArray,
		float[] normalsArray)
	{
		float furthestPoint = 0;
		for (int i = 0; i < vertices.size(); i++)
		{
			Vertex currentVertex = vertices.get(i);
			if (currentVertex.getLength() > furthestPoint)
			{ furthestPoint = currentVertex.getLength(); }
			Vector3f position = currentVertex.getPosition();
			Vector2f textureCoord = textures.get(currentVertex.getTextureIndex());
			Vector3f normalVector = normals.get(currentVertex.getNormalIndex());
			verticesArray[i * 3] = position.x;
			verticesArray[i * 3 + 1] = position.y;
			verticesArray[i * 3 + 2] = position.z;
			texturesArray[i * 2] = textureCoord.x;
			texturesArray[i * 2 + 1] = 1 - textureCoord.y;
			normalsArray[i * 3] = normalVector.x;
			normalsArray[i * 3 + 1] = normalVector.y;
			normalsArray[i * 3 + 2] = normalVector.z;
		}
		return furthestPoint;
	}

	private static void dealWithAlreadyProcessedVertex(Vertex previousVertex, int newTextureIndex,
		int newNormalIndex, List<Integer> indices, List<Vertex> vertices)
	{
		if (previousVertex.hasSameTextureAndNormal(newTextureIndex, newNormalIndex))
		{
			indices.add(previousVertex.getIndex());
		}
		else
		{
			Vertex anotherVertex = previousVertex.getDuplicateVertex();
			if (anotherVertex != null)
			{
				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());
			}
		}
	}

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