I get only a black screen

[jpct-env]

Hello,

I'm writing to explain my problem. I would like to use jpct-AE in order to create a very simple application with a 3D world inside it.
Immediately after I saw jpct-AE, I liked it, so I looked for examples but they are not as many as I expected. I tried hello world application for jpct-AE and worked fine, but after I changed some things to create something that was not just copied by the Internet, nothing worked anymore. For example, I would like to create a flat ground. I understand the logic in it, but if I apply it, it just doesn't work. Maybe it is something very easy to fix, because I didn't write so much code, just a test in order to get an idea of the way this library works. But I can't make this flat ground appear: when I launch this application, I just see a black screen and nothing in it... I also set up the ambient light, and a Sun (Light), but nothing appears anyway.

This is my source code:


MathMainActivity.java

Code Select Expand



package com.android.math_curve;

import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.opengles.GL10;

import com.threed.jpct.*;
import com.threed.jpct.util.BitmapHelper;
import com.threed.jpct.util.MemoryHelper;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.graphics.drawable.BitmapDrawable;
import android.opengl.GLSurfaceView;
import android.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MathMainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
GLSurfaceView mGLView = new GLSurfaceView(getApplication());

mGLView.setEGLConfigChooser(new GLSurfaceView.EGLConfigChooser() {
public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display) {
// Ensure that we get a 16bit framebuffer. Otherwise, we'll fall
// back to Pixelflinger on some device (read: Samsung I7500)
int[] attributes = new int[] { EGL10.EGL_DEPTH_SIZE, 16, EGL10.EGL_NONE };
EGLConfig[] configs = new EGLConfig[1];
int[] result = new int[1];
egl.eglChooseConfig(display, attributes, configs, 1, result);
return configs[0];
}
});

Renderer renderer = new MyRenderer();
mGLView.setRenderer(renderer);
setContentView(mGLView);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.math_main, menu);
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}

class MyRenderer implements Renderer
{

boolean bCalled = false;

FrameBuffer fb = null;
World world = null;
Light sun = null;
Object3D ground = null;

@Override
public void onDrawFrame(GL10 arg0) {
// TODO Auto-generated method stub
fb.clear();
world.renderScene(fb);
world.draw(fb);
fb.display();
}

public void Main3D()
{
world = new World();
world.setAmbientLight(150, 150, 150);
sun = new Light(world);
sun.setIntensity(250, 250, 250);
sun.setPosition(new SimpleVector(50, 20, 50));
ground = new Object3D(100);
TextureMgr.bitmap_as_texture_ex(getApplicationContext(), R.drawable.untitled, TextureManager.getInstance(), "mytexture", 1024, 1024);

int texture_id = TextureManager.getInstance().getTextureID("mytexture");

ground.addTriangle(
new SimpleVector(0, 0, 0),
0,
0,
new SimpleVector(100, 0, 0),
1024,
0,
new SimpleVector(0, 0, 100),
0,
1024,
texture_id);

ground.addTriangle(
new SimpleVector(100, 0, 0),
1024,
0,
new SimpleVector(100, 0, 100),
1024,
1024,
new SimpleVector(0, 0, 100),
0,
1024,
texture_id);



world.addObject(ground);

world.getCamera().setPosition(new SimpleVector(70, 35, 40));
ground.build();
ground.compile();
ground.setOrigin(new SimpleVector(0, 0, 0));
world.getCamera().lookAt(ground.getTransformedCenter());


}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
if( fb != null )
fb.dispose();
fb = new FrameBuffer(gl, width, height);
if( !bCalled )
{
bCalled = true;
Main3D();
}
}

@Override
public void onSurfaceCreated(GL10 arg0, EGLConfig arg1) {}

}
}






TextureMgr.java (a class I made to avoid writing multiple pieces of code)

Code Select Expand



package com.android.math_curve;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;

import com.threed.jpct.Texture;
import com.threed.jpct.TextureManager;
import com.threed.jpct.util.BitmapHelper;

public class TextureMgr {

public static boolean is_2_pow(int n)
{
int x = n;
if( x < 0 ) return false;
while( x % 2 == 0 )
{
x /= 2;
if( x == 1 )
{
return true;
}
}
return false;
}

public static void bitmap_as_texture_ex(Context app_context, int resource_id, TextureManager tm, String texture_name, int w, int h) throws IllegalArgumentException
{
if( TextureMgr.is_2_pow(w) == false || TextureMgr.is_2_pow(h) == false )
{
throw new IllegalArgumentException("FATAL EXCEPTION: width or height of texture is not a power of 2 in TextureMgr.bitmap_as_texture_ex()");
}
Bitmap bmp = TextureMgr.get_bitmap(app_context, resource_id);
if( bmp.getHeight() != h || bmp.getWidth() != w )
{
bmp = BitmapHelper.rescale(bmp, w, h);
}
TextureMgr.add_texture(tm, texture_name, bmp);
}

public static void bitmap_as_texture(Context app_context, int resource_id, TextureManager tm, String texture_name)
{
TextureMgr.add_texture(tm, texture_name, TextureMgr.get_bitmap(app_context, resource_id));
}

@SuppressWarnings("deprecation")
public static Bitmap get_bitmap(Context app_context, int resource_id)
{
return (new BitmapDrawable(app_context.getResources().openRawResource(resource_id))).getBitmap();
}

public static void add_texture(TextureManager tm, String texture_name, Bitmap bmp)
{
tm.addTexture(texture_name, TextureMgr.new_texture(bmp));
}

public static Texture new_texture(Bitmap bmp)
{
return new Texture(bmp);
}

}





In TextureMgr.java, there are a lot of functions, but not all are used in this test, some have been made for later use.


Could you explain me why I get just a black screen?

And another big question about the U/V coordinates:
For what I understood looking for what U/V coordinates exactly are, I think U/V coordinates are x/y coordinates of the picture that the texture contains.
So when I use it with Object3D.addTriangle(), with the couples of arguments (u,v), (u2,v2), (u3,v3) I draw a triangle in the texture and that triangle will be "printed" on the triangle in the Object3D.

Is it correct or is there something that is not correct? I ask it because I think it isn't a very good idea to deal with 3D world without complete understanding of textures, maybe it is like making a radio without the knowledge of electricity, do you agree? 


Please excuse me for my English, it isn't as perfect as I would like it to be, but I did my best to write this. If there is something not clear, please let me know and I'll try to make it more understandable.

I hope I will understand where the error is.
Waiting for an answer,

Richard

[EgonOlsen]

If you are getting a black screen, the first thing to try is to clear the background with some color instead of black to see if something of actually there, just black.
If that doesn't help, check your geometry and the camera. If you are sure that it should be visible, check the vertex order. The easiest way to do that is to call setCulling(false) on the object. If it appears then, your vertex ordering is wrong.

[EgonOlsen]

About UV: You are basically right. But the coordinates are normalized, i.e. don't use 0..1024 but 0..1 instead.

[jpct-env]

I made all working (after a lot of attemps). I used setCulling(false) and now the flat ground appears.

Thank you!

[EgonOlsen]

I made all working (after a lot of attemps). I used setCulling(false) and now the flat ground appears.

Thank you!

In that case, you are actually looking at it from the wrong side. This will effect the lighting, so you might want to rotate it 180° abound X or something like that.