缩放多边形：我可以知道多边形边界是否到达屏幕的边界？

Question

我想显示一个宽度为100％的正方形，然后，我想我必须缩放它（使用Z轴），直到多边形边框重启屏幕边框。

但我怎么能发现呢？

由于

MySurfaceView

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 rotación
private float oldY; //valor anterior de Y, para rotación
private final float TOUCH_SCALE = 0.2f;     //necesario para la rotación

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 rotación.
    xrot += xspeed;
    yrot += yspeed;
}

//si el surface cambia, resetea la vista, imagino que esto pasa cuando cambias de modo portrait/landscape o sacas el teclado físico en móviles 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;
}
}

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;
//Definición 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 código redimensionamos las imágenes 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 tamaño 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 tamaño 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 código transformamos imágenes no potencia de 2 en imágenes 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 versión 1.1 y generamos los Mipmaps por Flag. Si no, llamamos a nuestra propia implementación
    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 implementación 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;
    }
}
}

更新代码：

/////////////// NEW CODE FOR SCALING THE AR IMAGE TO THE DESIRED WIDTH /////////////////

        //and them, call the getCurrentModelView() for the ModelView matrix:  
        mg.getCurrentModelView(gl);  
        //values are stored at the mg.mModelView array, so:  
        //Log.i("Translation Z value", Float.toString(mg.mModelView[14]));//prints the current translation z value            
        //to get the current Projection matrix:  
        mg.getCurrentProjection(gl);  
        //values are stored at the mProjection, so:  
        //Log.i("First projection matrix value", Float.toString(mg.mProjection[0]));//prints the first projection matrix value 

        float [] modelMatrix = new float[16];
        float [] projMatrix = new float[16];        
        modelMatrix=mg.mModelView;
        projMatrix=mg.mProjection;
        // Now I am going to assume you set the model and projection matrices correctly
        // so I won't show that here.
        int [] mView = new int[4];
        // Fill this with your window width and height
        mView[0] = 0;
        mView[1] = 0;
        mView[2] = 800; //width
        mView[3] = 480; //height
        // Make sure you have 3 components in this array even if the screen only needs 2
        float [] outputCoords = new float[3];
        // Now I also assume that objX, objY, objZ are the coordinates of one of your borders
        GLU.gluProject(-1.0f, -1.0f, 0.0f, modelMatrix, 0, projMatrix, 0, mView, 0, outputCoords, 0);

Answer 1

使用gluProject将3D坐标投影到2D屏幕坐标。如果屏幕坐标为0或与您的宽度或高度匹配，则它会触摸屏幕边框。

修改以获取更多信息：

查看http://developer.android.com/reference/android/opengl/GLU.html上的定义。 基本上你将顶点的三个坐标作为objX objY objZ传递给它。您还可以将模型视图矩阵和投影矩阵传递给它，并将视图作为包含窗口大小的浮点数组传递给它。然后在win变量中得到结果窗口坐标。这是一个简单的例子：

float [] modelMatrix = new float[16];
float [] projMatrix = new float[16];

// Now I am going to assume you set the model and projection matrices correctly
// so I won't show that here.

float [] mView = new float[4];
// Fill this with your window width and height
view[0] = 0;
view[1] = 0;
view[2] = width;
view[3] = height;

// Make sure you have 3 components in this array even if the screen only needs 2
float [] outputCoords = new float[3]

// Now I also assume that objX, objY, objZ are the coordinates of one of your borders
gluProject(objX, objY, objZ, modelMatrix, 0, projMatrix, 0, view, 0, outputCoords, 0);

你还需要跟踪你的矩阵，因为某些版本的opengl for android不会这样做。请参阅此处的示例以进行矩阵跟踪：http://www.41post.com/1540/programming/android-opengl-get-the-modelview-matrix-on-15-cupcake