OpenGL片段着色器不写入fbo颜色缓冲区

我无法从片段着色器向FBO中的颜色缓冲区写入数据。 这个想法是绘制到这个纹理，然后将这个纹理绘制成四边形。 事情是，着色器在绘制到默认窗口缓冲区时起作用，因为如果我移除FBO，就会显示场景。 四边形的纹理也是如此，我用一个导入的纹理进行了尝试，结果如图所示。 我所得到的只是一个黑屏。 出了什么问题？ :(

创建FBO的代码：

glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);

glGenRenderbuffers(1, &depthbuff); //Add a depth renderbuffer for depth testing
glBindRenderbuffer(GL_RENDERBUFFER, depthbuff);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthbuff);

//Add the buffer to be drawn to and the buffer for the picking information
glGenTextures(1, &drawbuff);
glBindTexture(GL_TEXTURE_2D, drawbuff);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, drawbuff, 0);

glGenTextures(1, &pickingbuff);
glBindTexture(GL_TEXTURE_2D, pickingbuff);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, pickingbuff, 0);

代码渲染：

glBindFramebuffer(GL_FRAMEBUFFER, fbo);
GLenum buffers[] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, buffers);

shader->bind(); //If the three lines above are removed, it draws correctly to the window
drawStuff();

代码为四：

quadshader->bind();
glEnable(GL_TEXTURE_2D);
int drawTexID = quadshader->uniformLocation("drawTex");

glActiveTexture(GL_TEXTURE0);
//glBindTexture(GL_TEXTURE_2D, anotherTexture); //This works. A texture imported from a TGA
glBindTexture(GL_TEXTURE_2D, drawbuff);
glUniform1i(drawTexID, 0);

drawQuad();

最后，碎片着色器，我将它设置为将所有内容都绘制成纯色：

void main(void) {
    gl_FragData[0] = vec4(1.0, 1.0, 0.0, 1.0);
    gl_FragData[1] = vec4(0.0, 1.0, 1.0, 1.0);
}

编辑：如果它有任何帮助，整个事情是在一个Qt GLWidget。

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你是否注意确保你的纹理不是同时绑定到采样器（glBindTexture）和帧缓冲区？ 我相信如果您尝试在绑定到活动的采样器时写入纹理，或者尝试在附加到活动帧缓冲区时尝试采样纹理，则行为可能是错误或未定义。

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