繪製

Question

當OpenGL ES的幀緩衝區怪異鏡像我真的不能完成我的腦海解決此：

Previously我不能讓幀緩存的工作，但我想起來了去。但是，這個令人難以置信的怪異鏡像與幀緩衝區生成的紋理有關，我不知道爲什麼。基本上，我會嘗試使用GL_TRIANGLE_FAN在0,0處繪製紋理，並且紋理在右上角顯示爲正常（或多或少），但也出現在左下角，爲鏡像。如果我使用相同的紋理填充大部分或全部視區，結果是一個醜陋的z戰鬥重疊。

截圖可以做到這一點更公正。

原始圖像：

Original http://img301.imageshack.us/img301/1518/testsprite.png

在（0,0）

80x80 http://img407.imageshack.us/img407/8339/screenshot20100106at315.png

拉制80×80（0,0）

100x180 http://img503.imageshack.us/img503/2584/screenshot20100106at316.png

衝壓100x180博士分辨率320x480芒在（0,0）

320x480 http://img85.imageshack.us/img85/9172/screenshot20100106at317.png

這裏是我的代碼：

設置的觀點：

//Apply the 2D orthographic perspective. 
glViewport(0,0,320,480); 
glMatrixMode(GL_PROJECTION); 
glLoadIdentity(); 
glOrthof(0, 320, 480, 0, -10000.0f, 100.0f); 

//Disable depth testing. 
glMatrixMode(GL_MODELVIEW); 
glLoadIdentity(); 
glDisable(GL_DEPTH_TEST); 

//Enable vertext and texture coordinate arrays. 
glEnableClientState(GL_VERTEX_ARRAY); 
glEnableClientState(GL_TEXTURE_COORD_ARRAY); 

glShadeModel(GL_SMOOTH); 

glClearColor(0.5f, 0.5f, 0.5f, 1.0f); 

glGetError(); // Clear error codes 

sprite = [Sprite createSpriteFromImage:@"TestSprite.png"]; 
[sprite retain]; 

[self createTextureBuffer]; 

創建紋理緩存。

- (void) createTextureBuffer 
{ 
    // generate texture 
    glGenTextures(1, &bufferTexture); 
    glBindTexture(GL_TEXTURE_2D, bufferTexture); 
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);  // check if this is right 

    // generate FBO 
    glGenFramebuffersOES(1, &framebuffer); 
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, framebuffer); 
    // associate texture with FBO 
    glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, bufferTexture, 0); 

    // clear texture bind 
    glBindTexture(GL_TEXTURE_2D,0); 

    // check if it worked (probably worth doing :)) 
    GLuint status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES); 
    if (status != GL_FRAMEBUFFER_COMPLETE_OES) 
    { 
     printf("FBO didn't work..."); 
    } 
} 

運行渲染循環。

- (void)drawView 
{ 
    [self drawToTextureBuffer]; 

    // Make sure that you are drawing to the current context 
    [EAGLContext setCurrentContext:context]; 

    //Bind the GLView's buffer. 
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer); 
    glViewport(0, 0, 320, 480); 

    //Clear the graphics context. 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 

    //Push the matrix so we can keep it as it was previously. 
    glPushMatrix(); 

    //Rotate to match landscape mode. 
    glRotatef(90.0, 0, 0, 1); 
    glTranslatef(0.0f, -320.0f, 0.0f); 

    //Store the coordinates/dimensions from the rectangle. 
    float x = 0.0f; 
    float y = 0.0f; 
    float w = 480.0f; 
    float h = 320.0f; 

    // Set up an array of values to use as the sprite vertices. 
    GLfloat vertices[] = 
    { 
     x, y, 
     x, y+h, 
     x+w, y+h, 
     x+w, y 
    }; 

    // Set up an array of values for the texture coordinates. 
    GLfloat texcoords[] = 
    { 
     0, 0, 
     0, 1, 
     1, 1, 
     0, 1 
    }; 

    //Render the vertices by pointing to the arrays. 
    glVertexPointer(2, GL_FLOAT, 0, vertices); 
    glTexCoordPointer(2, GL_FLOAT, 0, texcoords); 

    // Set the texture parameters to use a linear filter when minifying. 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 

    //Enable 2D textures. 
    glEnable(GL_TEXTURE_2D); 

    //Bind this texture. 
    glBindTexture(GL_TEXTURE_2D, bufferTexture); 

    //Finally draw the arrays. 
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4); 

    //Restore the model view matrix to prevent contamination. 
    glPopMatrix(); 

    GLenum err = glGetError(); 
    if (err != GL_NO_ERROR) 
    { 
     NSLog(@"Error on draw. glError: 0x%04X", err); 
    } 


    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer); 
    [context presentRenderbuffer:GL_RENDERBUFFER_OES]; 
} 

第一遍，渲染循環會將圖像繪製到FBO中。

- (void)drawToTextureBuffer 
{ 
    if (!bufferWasCreated) 
    { 
     // render to FBO 
     glBindFramebufferOES(GL_FRAMEBUFFER_OES, framebuffer); 
     // set the viewport as the FBO isn't be the same dimension as the screen 
     glViewport(0, 0, 512, 512); 

     glPushMatrix(); 



     //Store the coordinates/dimensions from the rectangle. 
     float x = 0.0f; 
     float y = 0.0f; 
     float w = 320.0f; 
     float h = 480.0f; 

     // Set up an array of values to use as the sprite vertices. 
     GLfloat vertices[] = 
     { 
      x, y, 
      x, y+h, 
      x+w, y+h, 
      x+w, y 
     }; 

     // Set up an array of values for the texture coordinates. 
     GLfloat texcoords[] = 
     { 
      0, 0, 
      0, 1, 
      1, 1, 
      1, 0 
     }; 

     //Render the vertices by pointing to the arrays. 
     glVertexPointer(2, GL_FLOAT, 0, vertices); 
     glTexCoordPointer(2, GL_FLOAT, 0, texcoords); 

     // Set the texture parameters to use a linear filter when minifying. 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 

     //Allow transparency and blending. 
     glEnable(GL_BLEND); 
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 

     //Enable 2D textures. 
     glEnable(GL_TEXTURE_2D); 

     //Bind this texture. 
     glBindTexture(GL_TEXTURE_2D, sprite.texture); 

     //Finally draw the arrays. 
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4); 

     //Restore the model view matrix to prevent contamination. 
     glPopMatrix(); 

     GLenum err = glGetError(); 
     if (err != GL_NO_ERROR) 
     { 
      NSLog(@"Error on draw. glError: 0x%04X", err); 
     } 

     //Unbind this buffer. 
     glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0); 

     bufferWasCreated = YES; 
    } 
} 

Answer 1

你texcoords在- (void)drawView似乎是錯誤的

GLfloat texcoords[] = 
{ 
    0, 0, 
    0, 1, 
    1, 1, 
    0, 1  << HERE should be 1, 0 
};