Geek Answers Handbook

How to drag an OpenGL square with your finger?

Actually, I have an Android 1.5 app with the GLSurfaceView class that shows a simple square polygon on the screen.

I want to learn how to add new functionality, the functionality of moving a square that touches a finger. I mean, when the user touches the square and moves the finger, the square must stick to the finger until the finger releases the screen.

Any tutorials / code examples / help would be appreciated.

My code is:

public class MySurfaceView extends GLSurfaceView implements Renderer {  
private Context context;
private Square square;
private float xrot;                 //X Rotation
private float yrot;                 //Y Rotation
private float zrot;                 //Z Rotation
private float xspeed;               //X Rotation Speed
private float yspeed;               //Y Rotation Speed
private float z = -1.15f;           //Profundidad en el eje Z
private float oldX; //valor anterior de X, para rotaci贸n
private float oldY; //valor anterior de Y, para rotaci贸n
private final float TOUCH_SCALE = 0.2f;     //necesario para la rotaci贸n

//create the matrix grabber object in your initialization code  
private MatrixGrabber mg = new MatrixGrabber();           

private boolean firstTimeDone=false; //true si la aplicaci贸n ya ha sido inicializada.

public MySurfaceView(Context context, Bitmap image) {
    super(context);
    this.context = context;
    setEGLConfigChooser(8, 8, 8, 8, 16, 0); //fondo transparente
    getHolder().setFormat(PixelFormat.TRANSLUCENT); //fondo transparente
    //Transformamos esta clase en renderizadora
    this.setRenderer(this);
    //Request focus, para que los botones reaccionen
    this.requestFocus();
    this.setFocusableInTouchMode(true);
    square = new Square(image);                                 
}

public void onSurfaceCreated(GL10 gl, EGLConfig config) {       
    gl.glDisable(GL10.GL_DITHER);               //dithering OFF
    gl.glEnable(GL10.GL_TEXTURE_2D);            //Texture Mapping ON
    gl.glShadeModel(GL10.GL_SMOOTH);            //Smooth Shading 
    gl.glClearDepthf(1.0f);                     //Depth Buffer Setup
    gl.glEnable(GL10.GL_DEPTH_TEST);            //Depth Testing ON
    gl.glDepthFunc(GL10.GL_LEQUAL);
    gl.glClearColor(0,0,0,0); //fondo transparente
    gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST);         
    //Cargamos la textura del cubo.
    square.loadGLTexture(gl, this.context);
}

public void onDrawFrame(GL10 gl) {
    //Limpiamos pantalla y Depth Buffer
    gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
    gl.glLoadIdentity();
    //Dibujado
    gl.glTranslatef(0.0f, 0.0f, z);         //Move z units into the screen
    gl.glScalef(0.8f, 0.8f, 0.8f);          //Escalamos para que quepa en la pantalla
    //Rotamos sobre los ejes.
    gl.glRotatef(xrot, 1.0f, 0.0f, 0.0f);   //X
    gl.glRotatef(yrot, 0.0f, 1.0f, 0.0f);   //Y
    gl.glRotatef(zrot, 0.0f, 0.0f, 1.0f);   //Z
    //Dibujamos el cuadrado
    square.draw(gl);    
    //Factores de rotaci贸n.
    xrot += xspeed;
    yrot += yspeed;         


    if (!firstTimeDone)
    {       
        /////////////// NEW CODE FOR SCALING THE AR IMAGE TO THE DESIRED WIDTH /////////////////            
        mg.getCurrentProjection(gl); 
        mg.getCurrentModelView(gl);                     
        float [] modelMatrix = new float[16];
        float [] projMatrix = new float[16];
        modelMatrix=mg.mModelView;
        projMatrix=mg.mProjection;          
        int [] mView = new int[4];
        mView[0] = 0;
        mView[1] = 0;
        mView[2] = 800; //width
        mView[3] = 480; //height
        float [] outputCoords = new float[3];
        GLU.gluProject(-1.0f, -1.0f, z, modelMatrix, 0, projMatrix, 0, mView, 0, outputCoords, 0);

        int i=0;
        System.out.print(i);
       // firstTimeDone=true;
    }
}

//si el surface cambia, resetea la vista, imagino que esto pasa cuando cambias de modo portrait/landscape o sacas el teclado f铆sico en m贸viles tipo Droid.
public void onSurfaceChanged(GL10 gl, int width, int height) {
    if(height == 0) {                       
        height = 1;                         
    }
    gl.glViewport(0, 0, width, height);     //Reset Viewport
    gl.glMatrixMode(GL10.GL_PROJECTION);    //Select Projection Matrix
    gl.glLoadIdentity();                    //Reset Projection Matrix
    //Aspect Ratio de la ventana
    GLU.gluPerspective(gl, 45.0f, (float)width / (float)height, 0.1f, 100.0f);
    gl.glMatrixMode(GL10.GL_MODELVIEW);     //Select Modelview Matrix
    gl.glLoadIdentity();                    //Reset Modelview Matrix        

}

public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();
    switch (event.getAction()) 
    {
        case MotionEvent.ACTION_MOVE:
            //Calculamos el cambio
            float dx = x - oldX;
            float dy = y - oldY;
            xrot += dy * TOUCH_SCALE;
            yrot += dx * TOUCH_SCALE;
            //Log.w("XXXXXX", "ACTION_MOVE_NO_ZOOM");
            break;
    }
    oldX = x;
    oldY = y;
    return true; //El evento ha sido manejado
}

public void zoomIn(){ 
    z=z+0.2f;   
    if (z>-1.0f)
        z=-1.0f;
}
public void zoomOut(){ 
    z=z-0.2f; 
    if (z<-20.0f)
       z=-20.0f;
}
public void rotateL(){ 
    zrot=zrot+3.0f; 
}
public void rotateR(){ 
    zrot=zrot-3.0f; 
}   
public void reset()
{
    xrot=0;
    yrot=0;
    zrot=0;
    xspeed=0;
    yspeed=0;
    z = -5.0f;
}
}

This is my square class:

public class Square {
//Buffer de vertices
private FloatBuffer vertexBuffer;
//Buffer de coordenadas de texturas
private FloatBuffer textureBuffer;
//Puntero de texturas
private int[] textures = new int[3];
//El item a representar
private Bitmap image;
//Definici贸n de vertices

private float vertices[] = 
{ 
    -1.0f, -1.0f, 0.0f,     //Bottom Left
    1.0f, -1.0f, 0.0f,      //Bottom Right
    -1.0f, 1.0f, 0.0f,      //Top Left
    1.0f, 1.0f, 0.0f        //Top Right
};
/*  
private float vertices[] = 
{ 
-0.8f, -0.8f, 0.0f,     //Bottom Left
0.8f, -0.8f, 0.0f,      //Bottom Right
-0.8f, 0.8f, 0.0f,      //Top Left
0.8f, 0.8f, 0.0f 
};
*/
//Coordenadas (u, v) de las texturas    
/*
private float texture[] = 
{           
    //Mapping coordinates for the vertices
    0.0f, 0.0f,
    0.0f, 1.0f,
    1.0f, 0.0f,
    1.0f, 1.0f
};
*/
private float texture[] =
{
    //Mapping coordinates for the vertices
    0.0f, 1.0f,
    1.0f, 1.0f,
    0.0f, 0.0f,
    1.0f, 0.0f
};
//Inicializamos los buffers
public Square(Bitmap image) {
    ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4);
    byteBuf.order(ByteOrder.nativeOrder());
    vertexBuffer = byteBuf.asFloatBuffer();
    vertexBuffer.put(vertices);
    vertexBuffer.position(0);

    byteBuf = ByteBuffer.allocateDirect(texture.length * 4);
    byteBuf.order(ByteOrder.nativeOrder());
    textureBuffer = byteBuf.asFloatBuffer();
    textureBuffer.put(texture);
    textureBuffer.position(0);

    this.image=image;
} 
//Funcion de dibujado
public void draw(GL10 gl) {
    gl.glFrontFace(GL10.GL_CCW);
    //gl.glEnable(GL10.GL_BLEND);
    //Bind our only previously generated texture in this case
    gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
    //Point to our vertex buffer
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
    gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
    //Enable vertex buffer
    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
    //Draw the vertices as triangle strip
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
    //Disable the client state before leaving
    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
    //gl.glDisable(GL10.GL_BLEND);      
}
//Carga de texturas
public void loadGLTexture(GL10 gl, Context context) {
    //Generamos un puntero de texturas
    gl.glGenTextures(1, textures, 0);       
    //y se lo asignamos a nuestro array
    gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
    //Creamos filtros de texturas
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST);
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
    //Diferentes parametros de textura posibles GL10.GL_CLAMP_TO_EDGE
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT);
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT);     
    /*
    String imagePath = "radiocd5.png";
    AssetManager mngr = context.getAssets();
    InputStream is=null;
    try {
        is = mngr.open(imagePath);
    } catch (IOException e1) {  e1.printStackTrace();   }
    */
    //Get the texture from the Android resource directory
    InputStream is=null;
    /*
    if (item.equals("rim"))
        is = context.getResources().openRawResource(R.drawable.rueda);
    else if (item.equals("selector"))
        is = context.getResources().openRawResource(R.drawable.selector);
    */      
    /*
    is = context.getResources().openRawResource(resourceId);
    Bitmap bitmap = null;
    try {
        bitmap = BitmapFactory.decodeStream(is);
    } finally {
        try {
            is.close();
            is = null;
        } catch (IOException e) {
        }
    }
    */
    Bitmap bitmap =image;       
    //con el siguiente c贸digo redimensionamos las im谩genes que sean mas grandes de 256x256.
    int newW=bitmap.getWidth();
    int newH=bitmap.getHeight();
    float fact;
    if (newH>256 || newW>256)
    {
        if (newH>256)
        {
            fact=(float)255/(float)newH; //porcentaje por el que multiplicar para ser tama帽o 256
            newH=(int)(newH*fact); //altura reducida al porcentaje necesario
            newW=(int)(newW*fact); //anchura reducida al porcentaje necesario   
        }
        if (newW>256)
        {
            fact=(float)255/(float)newW; //porcentaje por el que multiplicar para ser tama帽o 256
            newH=(int)(newH*fact); //altura reducida al porcentaje necesario
            newW=(int)(newW*fact); //anchura reducida al porcentaje necesario
        }
        bitmap=Bitmap.createScaledBitmap(bitmap, newW, newH, true);
    }       
    //con el siguiente c贸digo transformamos im谩genes no potencia de 2 en im谩genes potencia de 2 (pot)
    //meto el bitmap NOPOT en un bitmap POT para que no aparezcan texturas blancas.
    int nextPot=256;
    int h = bitmap.getHeight();
    int w = bitmap.getWidth();
    int offx=(nextPot-w)/2; //distancia respecto a la izquierda, para que la imagen quede centrada en la nueva imagen POT
    int offy=(nextPot-h)/2; //distancia respecto a arriba, para que la imagen quede centrada en la nueva imagen POT
    Bitmap bitmap2 = Bitmap.createBitmap(nextPot, nextPot, Bitmap.Config.ARGB_8888); //crea un bitmap transparente gracias al ARGB_8888
    Canvas comboImage = new Canvas(bitmap2);
    comboImage.drawBitmap(bitmap, offx, offy, null);
    comboImage.save();

    //Usamos Android GLUtils para espcificar una textura de 2 dimensiones para nuestro bitmap
    GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap2, 0);

    //Checkeamos si el GL context es versi贸n 1.1 y generamos los Mipmaps por Flag. Si no, llamamos a nuestra propia implementaci贸n
    if(gl instanceof GL11) {
        gl.glTexParameterf(GL11.GL_TEXTURE_2D, GL11.GL_GENERATE_MIPMAP, GL11.GL_TRUE);
        GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap2, 0);
    } else {
        buildMipmap(gl, bitmap2);
    }   
    //Limpiamos los bitmaps
    bitmap.recycle();
    bitmap2.recycle();
}
//Nuestra implementaci贸n de MipMap. Escalamos el bitmap original hacia abajo por factor de 2 y lo asignamos como nuevo nivel de mipmap
private void buildMipmap(GL10 gl, Bitmap bitmap) {
    int level = 0;
    int height = bitmap.getHeight();
    int width = bitmap.getWidth();
    while(height >= 1 || width >= 1) {
        GLUtils.texImage2D(GL10.GL_TEXTURE_2D, level, bitmap, 0);
        if(height == 1 || width == 1) {
            break;
        }
        level++;
        height /= 2;
        width /= 2;
        Bitmap bitmap2 = Bitmap.createScaledBitmap(bitmap, width, height, true);
        bitmap.recycle();
        bitmap = bitmap2;
    }
}
}
+5
source share
3 answers

Have you looked at the Android tutorial code? They have something very similar to examples with OpenGL ES 1 and 2.

OpenGL ES 1 . http://developer.android.com/resources/tutorials/opengl/opengl-es10.html#touch

, AddMotion glrotatef gltranslatef;

, , . , , , , ( , ). winZ , gluunproject. , winZ, "z". z , ?

, GLWrapper GLSurfaceView :

    mGLView.setGLWrapper(new GLWrapper() {
        public GL wrap(GL gl) {
            return new MatrixTrackingGL(gl);
        }

    });

GLSurfaceView/Renderer...

public float[] unproject(GL10 gl, float x, float y) {
    mMatrixGrabber.getCurrentState(gl);
    int[] view = {0,0,this.getWidth(), this.getHeight()};
    float[] pos = new float[4];
    float[] result = null;
    int retval = GLU.gluUnProject(x, y, -z, 
            mMatrixGrabber.mModelView, 0,
            mMatrixGrabber.mProjection, 0,
            view, 0, 
            pos, 0);
    if (retval != GL10.GL_TRUE) {
        Log.e("unproject", GLU.gluErrorString(retval));
    } else {
        result = new float[3];
        result[0] = pos[0] / pos[3];
        result[1] = pos[1] / pos[3];
        result[2] = pos[2] / pos[3];
        result = pos;
    }
    return result;
}

TouchEvent,

    switch (event.getAction()) 
    {
        case MotionEvent.ACTION_MOVE:
            //Calculamos el cambio
            float dx = x - oldX;
            float dy = y - oldY;
            xrot += dy * TOUCH_SCALE;
            yrot += dx * TOUCH_SCALE;
            //Log.w("XXXXXX", "ACTION_MOVE_NO_ZOOM");
            touching = true;
            break;
        case MotionEvent.ACTION_UP:
            xrot = 0;
            yrot = 0;
            zrot = 0;
            touching = false;
            break;
    }

translate/scale/rotation:

    if (touching) {
        float[] point = unproject(gl, oldX, (this.getHeight() - oldY));
        if (point == null) {
            Log.e("Draw", "No Point");
        } else {
            gl.glTranslatef(point[0], point[1], 0);
        }
    }

, , .

+5

min3d http://code.google.com/p/min3d/

opengl

+2

I would use an ontouch receiver waiting for action down. After this is called, find the position of the finger through getrawx or y, and then redraw the square in canvas opengl respectively. Here is a link with a good tutorial. http://www.zdnet.com/blog/burnette/how-to-use-multi-touch-in-android-2-part-5-implementing-the-drag-gesture/1789?tag=content;siu- container

+1
source

More articles:


All Articles