/*

ahbejarano

.obj mesh loader class.

*/

package geetransit.minecraft05.engine;

import java.util.*;

import org.joml.*;

public class ObjLoader {

public static Mesh loadMesh(String file) throws Exception {

List<Vector3f> vertices = new ArrayList<>();

List<Vector2f> textures = new ArrayList<>();

List<Face> faces = new ArrayList<>();

Utils.loadLinesStream(file).forEach(line -> {

String[] tokens = line.split("\\s+");

switch (tokens[0]) {

case "v":

// Geometric vertex

vertices.add(new Vector3f(

Float.parseFloat(tokens[1]),

Float.parseFloat(tokens[2]),

Float.parseFloat(tokens[3])

));

break;

case "vt":

// Texture coordinate

textures.add(new Vector2f(

Float.parseFloat(tokens[1]),

Float.parseFloat(tokens[2])

));

break;

case "f":

Face face = new Face(tokens[1], tokens[2], tokens[3]);

faces.add(face);

break;

default:

// Ignore other lines

break;

}

});

return reorderLists(vertices, textures, faces);

}

private static Mesh reorderLists(

List<Vector3f> vertexList,

List<Vector2f> coordList,

List<Face> faceList

) {

List<Integer> posList = new ArrayList<>();

// Create position array in the order it has been declared

float[] posArray = new float[vertexList.size() * 3];

for (int i = 0; i < vertexList.size(); i++) {

Vector3f pos = vertexList.get(i);

posArray[i*3 + 0] = pos.x;

posArray[i*3 + 1] = pos.y;

posArray[i*3 + 2] = pos.z;

}

float[] coordArray = new float[vertexList.size() * 2];

for (Face face : faceList)

for (IndexGroup group : face.groups)

processFaceVertex(group, coordList, posList, coordArray);

// int[] indexArray = new int[indices.size()];

int[] indexArray = Utils.intListToArray(posList);

return new Mesh(posArray, indexArray, coordArray);

}

private static void processFaceVertex(

IndexGroup group,

List<Vector2f> coordList,

List<Integer> posList,

float[] coordArray

) {

// Set pos for vertex coordinates

int pos = group.pos;

posList.add(pos);

// Reorder texture coordinates

if (group.coord != IndexGroup.NO_VALUE) {

Vector2f coord = coordList.get(group.coord);

coordArray[pos*2 + 0] = coord.x;

coordArray[pos*2 + 1] = 1 - coord.y;

}

}

protected static class IndexGroup {

public static final int NO_VALUE = -1;

public int pos;

public int coord;

public IndexGroup() {

this.pos = NO_VALUE;

this.coord = NO_VALUE;

}

}

protected static class Face {

// List of pos groups for a face triangle (3 vertices per face).

public final IndexGroup[] groups;

public Face(String v1, String v2, String v3) {

this.groups = new IndexGroup[3];

// Parse the lines

this.groups[0] = parseLine(v1);

this.groups[1] = parseLine(v2);

this.groups[2] = parseLine(v3);

}

private IndexGroup parseLine(String line) {

IndexGroup group = new IndexGroup();

String[] tokens = line.split("/");

int length = tokens.length;

group.pos = Integer.parseInt(tokens[0]) - 1;

if (length <= 1)

return group;

// It can be empty if the obj does not define text coords

if (tokens[1].length() != 0)

group.coord = Integer.parseInt(tokens[1]) - 1;

if (length <= 2)

return group;

return group;

}

}

}