Wall of text below:
I'm having trouble loading up a correct cube mesh using OpenGL ES 2.0 on an Android device running ICS.
From what I observed, I see that the vertices of the cube is not only distorted, but also some of the vertices have incorrect vertex positions in the world matrix. You can tell by looking at some of the snapshots taken below:
I have checked and confirmed that my OBJ file parser is not causing any troubles, by comparing the values copied into the buffer objects to the values in the OBJ file itself. I have used the software, Blender, to re-create the cube mesh by exporting and overwriting the OBJ files. I have exclusively enabled "Triangulate faces" and "Include normal" in the Blender -> Export options. None of the actions above worked.
I have also checked my shader codes to see if they compiled and are referencing the correct variables. So far, there's nothing wrong. The OpenGL ES did not spit out any errors, when I was using glGetProgramInfo() and glGetShaderInfo(). They all pass. And I can see my model clearly, just that I didn't add any ambient lighting and shadows to the mesh.
I have somehow recreated the problem that I had asked a month ago prior that was solved by fixing the transformation matrix calculation methods. But this time, it's no longer the matrices. I have checked and confirmed that the transformation matrices are not causing the problem.
The cube that was exported/overwritten is the same cube mesh I had used in the Stack Overflow question above. Which looked like this below: (Left side: Perspective view of the back side of the cube mesh. Right side: Orthogonal view of the front size of the cube mesh.)
Below is an attachment of the Android APK, packed in a ZIP file.
[attachment=14673:3DOpenGL.zip]
Below is the project source file attached:
[attachment=14674:3DOpenGL_source.zip]
And below are some of the source code that I used to load the cube mesh model: (Model class, OBJ model loader static method) They are shown for easier lookup.
package models;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;
import java.util.ArrayList;
import android.content.Context;
import android.content.res.AssetManager;
import android.util.Log;
public class Model {
protected FloatBuffer vertexBuffer;
protected ShortBuffer indexBuffer;
public static Model loadOBJModel(Context c, String filename) {
ArrayList<Float> tempVertices = new ArrayList<Float>();
ArrayList<Float> tempNormals = new ArrayList<Float>();
ArrayList<Short> tempVertexIndices = new ArrayList<Short>();
ArrayList<Short> tempNormalIndices = new ArrayList<Short>();
Model model = new Model();
try {
AssetManager manager = c.getAssets();
BufferedReader reader = new BufferedReader(new InputStreamReader(manager.open(filename)));
String line;
while ((line = reader.readLine()) != null) {
if (line.startsWith("v")) {
for (int i = 0; i < 3; i++) {
tempVertices.add(Float.valueOf(line.split(" ")[i + 1]));
}
}
else if (line.startsWith("vn")) {
for (int i = 0; i < 3; i++) {
tempNormals.add(Float.valueOf(line.split(" ")[i + 1]));
}
}
else if (line.startsWith("f")) {
String[] tokens = line.split(" ");
if (tokens[1].contains("/")) {
for (int i = 0; i < 3; i++) {
tempVertexIndices.add(Short.valueOf(tokens[i + 1].split("/")[0]));
tempNormalIndices.add(Short.valueOf(tokens[i + 1].split("/")[2]));
}
}
else {
for (int i = 0; i < 3; i++) {
tempVertexIndices.add(Short.valueOf(tokens[i + 1]));
}
}
}
}
//TODO: Will add lighting back once everything is confirmed to work properly.
float[] vertices = createFloatArray(tempVertices);
//float[] normals= createFloatArray(tempNormals);
short[] vertexIndices = createShortArray(tempVertexIndices);
//short[] normalIndices = createShortArray(tempNormalIndices);
model.vertexBuffer = ByteBuffer.allocateDirect(vertices.length * 4).order(ByteOrder.nativeOrder()).asFloatBuffer();
model.vertexBuffer.put(vertices).position(0);
model.indexBuffer = ByteBuffer.allocateDirect(vertexIndices.length * 2).order(ByteOrder.nativeOrder()).asShortBuffer();
model.indexBuffer.put(vertexIndices).position(0);
}
catch (Exception e) {
e.printStackTrace();
Log.e("DEBUG loadCube()", "Exception error caught.", e);
}
return model;
}
//--------------------------------------
private static float[] createFloatArray(ArrayList<Float> list) {
float[] array = new float[list.size()];
for (int i = 0; i < array.length; i++) {
Float f = list.get(i);
array = (f != null ? f : Float.NaN);
}
return array;
}
private static short[] createShortArray(ArrayList<Short> list) {
short[] array = new short[list.size()];
for (int i = 0; i < array.length; i++) {
Short f = list.get(i);
array = (f != null ? f : 0);
}
return array;
}
}
Below is the Cube class: (Cube class, with transformation matrices, vertex and fragment shader codes, and the initialization)
package models;
import java.util.Arrays;
import android.content.Context;
import android.opengl.GLES20;
import android.opengl.Matrix;
import android.util.Log;
public class Cube {
private String vertexCode = "" +
"attribute vec4 a_position; \n" +
"uniform mat4 u_mvpMatrix; \n" +
"void main() { \n" +
" gl_Position = u_mvpMatrix * a_position; \n" +
"} \n";
private String fragmentCode = "" +
"precision mediump float; \n" +
"void main() { \n" +
" gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);\n" +
"} \n";
private int shaderProgram;
private int attribute_Position;
private int uniform_mvpMatrix;
private float angle;
private Model model;
public Cube(Context c, String filename){
model = Model.loadOBJModel(c, filename);
}
public void setup(){
int vertexShader = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
GLES20.glShaderSource(vertexShader, vertexCode);
GLES20.glCompileShader(vertexShader);
int fragmentShader = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
GLES20.glShaderSource(fragmentShader, fragmentCode);
GLES20.glCompileShader(fragmentShader);
shaderProgram = GLES20.glCreateProgram();
GLES20.glAttachShader(shaderProgram, vertexShader);
GLES20.glAttachShader(shaderProgram, fragmentShader);
GLES20.glBindAttribLocation(shaderProgram, 1, "a_position");
GLES20.glLinkProgram(shaderProgram);
int[] linked = new int[1];
GLES20.glGetProgramiv(shaderProgram, GLES20.GL_LINK_STATUS, linked, 0);
if (linked[0] == 0) {
Log.e("DEBUG setup()", "Shader code error.");
Log.e("DEBUG setup()", GLES20.glGetProgramInfoLog(shaderProgram));
GLES20.glDeleteProgram(shaderProgram);
return;
}
GLES20.glDeleteShader(vertexShader);
GLES20.glDeleteShader(fragmentShader);
attribute_Position = GLES20.glGetAttribLocation(shaderProgram, "a_position");
uniform_mvpMatrix = GLES20.glGetUniformLocation(shaderProgram, "u_mvpMatrix");
GLES20.glEnableVertexAttribArray(attribute_Position);
}
public void draw(float[] mMatrix, float[] vMatrix, float[] pMatrix){
float[] mvpMatrix = new float[16];
Matrix.setIdentityM(mMatrix, 0);
Matrix.translateM(mMatrix, 0, 0f, -2.5f, -1.5f);
Matrix.rotateM(mMatrix, 0, angle, 0f, 1f, 0f);
// This is the transformation matrices that I had a problem with a month ago. It has been solved by using
// an array copy of the original matrix. The behavior is already defined in the Android documentation.
Matrix.multiplyMM(mvpMatrix, 0, vMatrix, 0, mMatrix, 0);
Matrix.multiplyMM(mvpMatrix, 0, pMatrix, 0, Arrays.copyOf(mvpMatrix, 16), 0);
GLES20.glUseProgram(shaderProgram);
GLES20.glVertexAttribPointer(attribute_Position, 3, GLES20.GL_FLOAT, false, 3 * 4, model.vertexBuffer);
GLES20.glUniformMatrix4fv(uniform_mvpMatrix, 1, false, mvpMatrix, 0);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, model.indexBuffer.capacity(), GLES20.GL_UNSIGNED_SHORT, model.indexBuffer);
angle = ++angle % 360f;
}
}
Oh boy, there's a lot of information provided just so I can nail this bug, squish it, and move on. I really need help on this one. Been looking for answers on Google search, and came up dry. The first three results are not what I wanted. The second result is the link that I asked for solutions a month ago. The rest of the results are tutorials.
If there's something I might have missed. Please let me know.
