Question

我正在尝试渲染到纹理，然后复制该纹理并通过后处理运行它，然后将过滤后的图像与原始图像合并。我已经得到它所以我可以渲染到纹理，然后处理它并显示它，但我只能处理一次。我真的不确定会出现什么问题。

这是我的FBO设置代码：

for (int i = 0; i < 3; i++) {
    glGenFramebuffers(1, &postfboId[i]);
    glGenTextures(1, &postTextureId[i]);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, postTextureId[i]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    //float color[4] = {0.0, 0.0, 0.0, 1.0};
    //glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, color);
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, screenSize.x, screenSize.y, 0, GL_RGB, GL_UNSIGNED_BYTE, 0);

    // create a framebuffer object
    glBindFramebuffer(GL_FRAMEBUFFER, postfboId[i]);


    glGenRenderbuffers(1, &depthrenderbuffer[i]);
    glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer[i]);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, screenSize.x, screenSize.y);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer[i]);


    // attach the texture to FBO depth attachment point
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D, postTextureId[i], 0);

    }
    GLenum DrawBuffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2};
    glDrawBuffers(1, DrawBuffers);
    // check FBO status
    FBOstatus = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if(FBOstatus != GL_FRAMEBUFFER_COMPLETE)
        printf("hey man, you might want to sit down a minute, i didn't want to have to say this to you, but the FBO failed.\n");

我想也许我需要glDrawBuffers来制作3而不是1，但这只会导致FBO不完整。这是我的渲染代码：

glBindFramebuffer(GL_FRAMEBUFFER,postfboId[0]);
sf::Vector2u size = screenSize;
changeSize(size.x, size.y);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); 
//clear viewport
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glUseProgram(prog);

glPushMatrix();

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
setLookat();
glCullFace(GL_BACK);
setLights();
drawObjs();

glPopMatrix();

//first round post process
glClearColor(0, 0, 0, 1);
glUseProgram(postProg);

glBindFramebuffer(GL_FRAMEBUFFER,postfboId[1]);
glUniform1i(postProcessMode, 1);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glOrtho(0,screenSize.x,0,screenSize.y,-1,20);
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glPushMatrix();
glLoadIdentity();
glColor4f(1,1,1,1);
glUniform1i(texUniform3, 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,postTextureId[0]);
glEnable(GL_TEXTURE_2D);
glTranslated(0,0,-19.5);
glBegin(GL_QUADS);
glTexCoord2d(0,0);glVertex3f(0,0,0);
glTexCoord2d(1,0);glVertex3f(screenSize.x,0,0);
glTexCoord2d(1,1);glVertex3f(screenSize.x,screenSize.y,0);
glTexCoord2d(0,1);glVertex3f(0,screenSize.y,0);
glEnd();


// round 2 post
glUniform1i(postProcessMode, 2);
glBindFramebuffer(GL_FRAMEBUFFER,0);

glUniform1i(texUniform3, 3);
glActiveTexture(GL_TEXTURE3);
// bind postTextureId[0] to draw real screen.
glBindTexture(GL_TEXTURE_2D,postTextureId[1]);
glEnable(GL_TEXTURE_2D);
glTranslated(0,0,0.5);
glBegin(GL_QUADS);
glTexCoord2d(0,0);glVertex3f(0,0,0);
glTexCoord2d(1,0);glVertex3f(screenSize.x,0,0);
glTexCoord2d(1,1);glVertex3f(screenSize.x,screenSize.y,0);
glTexCoord2d(0,1);glVertex3f(0,screenSize.y,0);
glEnd();
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();

无论出于何种原因，将FBO纹理绘制到另一个FBO会导致无意义，但将FBO纹理绘制到屏幕上就可以了。此外，所有3个FBO都工作，而不是同时工作，这很奇怪，因为我有另一个FBO只有一个深度缓冲区，可以正确显示阴影贴图。

Answer 1

一个显而易见的问题是，除了第一个渲染目标之外，您还缺少glClear()个调用。你在绑定fbo 0之后调用它一次：

glBindFramebuffer(GL_FRAMEBUFFER,postfboId[0]);
...
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

但是你还需要在绑定fbo 1之后清除：

glBindFramebuffer(GL_FRAMEBUFFER,postfboId[1]);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

并绑定默认帧缓冲区后：

glBindFramebuffer(GL_FRAMEBUFFER,0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

您的glPushMatrix()和glPopMatrix()部分电话看起来也有点可疑。但是如果不看完整个代码就很难判断它们是不正确的。您可能需要仔细检查它们是否均衡，并且在调用它们时您处于正确的矩阵模式。例如，在这个序列中：

glMatrixMode(GL_PROJECTION);
glPopMatrix();
glPushMatrix();
glLoadIdentity();

glPopMatrix()和glPushMatrix()来电是多余的。如果有的话，它们可能是有害的，因为如果您之前没有呼叫glPushMatrix()，则会出现错误。否则，它将首先将前一个矩阵复制到顶部条目，但随后立即用身份矩阵覆盖它。这与单独调用glLoadIdentity()相同。

OpenGL：一次只有一个FBO可以使用

1 个答案: