Question

如果问题太天真，我是opengGL的新手和借口。我正在通过一些tuturials寻求帮助来学习这个。我有一个小程序，我在GLSurfaceView上绘制纹理。

我想从0,0坐标开始按顺序绘制多个纹理（位图图像）。另外，我需要屏幕上的图像有一些差距。请帮忙。我是否需要更改顶点缓冲区的位置。请建议。

这是我的渲染器代码。

public class GlRenderer implements Renderer{

    private Square  square; // square1
    private Context context;

    /** Constructor to set the handed over context */
    public GlRenderer(Context context) {
        this.context = context;

        // initialise the square
        this.square = new Square();
    }

    public void onDrawFrame(GL10 gl) {
        // clear Screen and Depth Buffer
        gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);

        // Reset the Modelview Matrix
        gl.glLoadIdentity();

        // Drawing
        gl.glTranslatef(0.0f, 0.0f, -5.0f);     // move 5 units INTO the screen
        square.draw(gl);                        // Draw the triangle
        //gl.glTranslatef(0.0f, 0.0f, 0.0f);        // move 5 units INTO the screen
        //square2.draw(gl);                     // Draw the triangle
    }

    public void onSurfaceChanged(GL10 gl, int width, int height) {
        if(height == 0) {                       //Prevent A Divide By Zero By
            height = 1;                         //Making Height Equal One
        }

        gl.glViewport(0, 0, width, height);     //Reset The Current Viewport
        gl.glMatrixMode(GL10.GL_TEXTURE);   //Select The Projection Matrix
        gl.glLoadIdentity();                    //Reset The Projection Matrix

        //Calculate The Aspect Ratio Of The Window
        GLU.gluPerspective(gl, 45.0f, (float)width / (float)height, 0.1f, 100.0f);

        gl.glMatrixMode(GL10.GL_MODELVIEW);     //Select The Modelview Matrix
        gl.glLoadIdentity();                    //Reset The Modelview Matrix
    }

    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        // Load the texture for the square
        square.loadGLTexture(gl, this.context);

        gl.glEnable(GL10.GL_TEXTURE_2D);            //Enable Texture Mapping ( NEW )
        gl.glShadeModel(GL10.GL_SMOOTH);            //Enable Smooth Shading
        gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);    //Black Background
        gl.glClearDepthf(1.0f);                     //Depth Buffer Setup
        gl.glEnable(GL10.GL_DEPTH_TEST);            //Enables Depth Testing
        gl.glDepthFunc(GL10.GL_LEQUAL);             //The Type Of Depth Testing To Do

        //Really Nice Perspective Calculations
        gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); 

    }
}

这是方形代码

public class Square {
    private FloatBuffer vertexBuffer;   // buffer holding the vertices
    private float vertices[] = {
            -1.0f, -.25f,  0.0f,    // V1 - bottom left
            -1.0f, .25f,  0.0f,     // V2 - top left
            1.0f, -.25f,  0.0f,     // V3 - bottom right
            1.0f, .25f,  0.0f       // V4 - top right
    };

    private FloatBuffer textureBuffer;  // buffer holding the texture coordinates
    private float texture[] = {         
            // Mapping coordinates for the vertices
            0.0f, 1.0f,     // top left     (V2)
            0.0f, 0.0f,     // bottom left  (V1)
            1.0f, 1.0f,     // top right    (V4)
            1.0f, 0.0f      // bottom right (V3)
    };

    /** The texture pointer */
    private int[] textures = new int[1];

    public Square() {
        // a float has 4 bytes so we allocate for each coordinate 4 bytes
        ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * 4);
        byteBuffer.order(ByteOrder.nativeOrder());

        // allocates the memory from the byte buffer
        vertexBuffer = byteBuffer.asFloatBuffer();

        // fill the vertexBuffer with the vertices
        vertexBuffer.put(vertices);

        // set the cursor position to the beginning of the buffer
        vertexBuffer.position(0);

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

    /**
     * Load the texture for the square
     * @param gl
     * @param context
     */
    public void loadGLTexture(GL10 gl, Context context) {
        // loading texture
        Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(),
                R.drawable.progressbar_bg);

        // generate one texture pointer
        gl.glGenTextures(1, textures, 0);
        // ...and bind it to our array
        gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);

        // create nearest filtered texture
        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);

        //Different possible texture parameters, e.g. 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);

        // Use Android GLUtils to specify a two-dimensional texture image from our bitmap 
        GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);

        // Clean up
        bitmap.recycle();
    }


    /** The draw method for the square with the GL context */
    public void draw(GL10 gl) {
        // bind the previously generated texture
        gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);

        // Point to our buffers
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

        // Set the face rotation
        gl.glFrontFace(GL10.GL_CW);

        // Point to our vertex buffer
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
        gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);

        // 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);
    }
}

我无法在视图上看到纹理的实际大小。我正在玩gl.glTranslatef（0.0f，0.0f，-5.0f）;操纵屏幕上纹理的坐标。但仍然无法获得实际的图像大小，并将纹理图像定位在从0,0坐标开始的所需循环中。

Answer 1

我通过正确使用glTranslate（）解决了这个问题。现在我明白，translate将表面的最后翻译值作为当前位置。我已经使用固定的x和z坐标进行了更改，并在每次绘制纹理后更改y。我做了以下事情：

        float x = -1.0f;
    float y = 1.5f;
    float z = -5.0f;

    // Drawing
    gl.glTranslatef(x, y, z);
    square1.draw(gl);                       // Draw the square
    gl.glTranslatef(0.0f, -0.50f, 0.0f);
    square2.draw(gl);                       // Draw the square
    gl.glTranslatef(0.0f, -0.50f, 0.0f);
    square2.draw(gl);                       // Draw the square
    gl.glTranslatef(0.0f, -0.50f, 0.0f);
    square2.draw(gl);                       // Draw the square

Answer 2

我认为绘图对象和绘制位图（像素操作）之间存在混淆

根据您的要求＆＃34;我想从0,0坐标开始按顺序绘制多个纹理（位图图像）。另外，我需要屏幕上的图像有一些差距。请帮忙。我是否需要更改顶点缓冲区的定位＆＃34;。你最好选择绘制位图。请参阅api glBitmap，glDrawPixels等

纹理。您应用的概念/方法是正确的。您正在（-1，-1）和（1,1）之间绘制一个矩形。纹理映射似乎是正确的。但是，你需要和api一起玩 glTexParameterf（GL_TEXTURE_2D，GL_TEXTURE_WRAP_S，GL_REPEAT或CLAMP）;
glTexParameterf（GL_TEXTURE_2D，GL_TEXTURE_WRAP_T，GL_REPEAT）;
（PS-PLease适当地使用基于android的apis）

当您使用glTranslatef进行实验时，对象也会移动（与纹理一起）。

想象一下，你正在画衬衫，带有图案。图案坐标与衬衫有关。使用纹理apis将图案定位在衬衫上。而translatef调用会移动世界坐标系，但模式不会改变。

Answer 3

如果您正在使用像素绘制功能（在您直接绘制到屏幕缓冲区的位置），请使用apis这样的glPixelZoom。您可以使用负值来改变方向

如果您尝试使用模型转换，请使用glRotate API。使用平移和旋转的组合。

从0,0坐标在OpenGL Android中绘制纹理

3 个答案: