我需要显示一个方形多边形,其宽度为屏幕宽度的100%,然后,我必须缩放它(使用Z轴),直到多边形边框为屏幕边框设置为止.
我正在尝试使用gluProject将3D坐标投影到2D屏幕坐标.如果屏幕坐标为0或与宽度或高度匹配,则它将触摸屏幕边框.
问题是出了问题,outputCoords用gluProject返回的数组给了我这些值:0,0,0.5,但是我的方块以sreen为中心,并且Z = -5.0f !!!!
我不明白这些价值......
这是我用于在屏幕上获取方形poligon的2D投影的代码:
此代码位于GLSurfaceView类的onSurfaceCreated方法上,它必须在另一个方法中使用？哪里？
/////////////// NEW CODE FOR SCALING THE AR IMAGE TO THE DESIRED WIDTH /////////////////
mg.getCurrentModelView(gl);
mg.getCurrentProjection(gl);
float [] modelMatrix = new float[16];
float [] projMatrix = new float[16];
modelMatrix=mg.mModelView;
projMatrix=mg.mProjection;
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];
// objX, objY, objZ are the coordinates of one of the borders
GLU.gluProject(-1.0f, -1.0f, 0.0f, modelMatrix, 0, projMatrix, 0, mView, 0, outputCoords, 0);
这是我的方形课:
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 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;
}
}
}
Chr*_*ica 11
gluProject 确切地说,固定功能转换管道也会做什么:
通过附加1作为第四个坐标,将3D顶点扩展为齐次坐标:v[3]=1.
然后将这个同质顶点乘以模型视图矩阵和投影矩阵:v'=P*M*v.
然后出现了分裂.由第四分隔的坐标,我们考虑透视畸变(如果你有一个正投影例如使用glOrtho,则v'[3]==1并没有透视变形)v"=v'/v'[3].
现在,观察体积(场景的可见区域)中的所有内容都已转换为标准化设备坐标,即[-1,1] - 立方体.所以需要做的是将其转换为屏幕坐标[0,w] x [0,h]:x=w * (v"[0]+1) / 2和y = h * (v"[1]+1) / 2.最后,z坐标从[-1,1]变换为[0,1],得到写入深度缓冲区的标准化深度值:z = (v"[2]+1) / 2.
因此理解z值发生的关键是要意识到,相机的距离(视图空间中的z值)首先被投影矩阵转换为[-1,1]范围,具体取决于近-far范围(您输入的近和远值glOrtho,glFrustum或gluPerspective).然后将该归一化值转换为[0,1]范围,以得到最终深度值,该深度值被写入深度缓冲区并gluProject计算为窗口坐标的z值.
所以你实际得到的(0, 0, 0.5)是屏幕的左下角,深度为0.5.与正交矩阵(没有任何透视畸变)和身份模型视图矩阵的坐标,这将是平等的(left, bottom, (far-near)/2),在那里bottom,left,near和far你投入的相应参数glOrtho的函数调用(或者具有类似功能的东西).因此,顶点位于观察体积的近远距离和左下角的中间(从相机看).但这不适用于透视投影,因为在这种情况下,从视空间z坐标到深度值的变换不是线性的(当然,尽管仍然是单调的).
由于你放入了顶点(-1, -1, 0),这可能意味着你的模型视图矩阵是同一性的,你的投影矩阵对应于一个用glOrtho(-1, 1, -1, 1, -1, 1)它创建的矩阵,它也几乎是单位矩阵(虽然有一个镜像的z值,但因为输入z是0,你可能没注意到它).因此,如果这些不是您期待的值(gluProject当然,在理解了其工作原理之后),也可能只是您的矩阵未被正确检索而您只是获得了身份矩阵而不是您的实际模型视图和投影矩阵.
所以我认为你的gluProject功能没有任何问题.您还可以查看此问题的答案,以便更深入地了解OpenGL的默认转换管道.虽然随着顶点着色器的出现,某些阶段可以以不同的方式计算,但您通常仍然遵循惯用模型 - >视图 - >投影方法.