在iOS上使用OpenGL ES 2.0创建FBO的最小示例

Question

我在创建FBO时遇到问题,然后在我的iOS应用程序中将其用作纹理.我在github上传了我的应用程序的精简版,显示了问题.我只是一个空白的屏幕,有一种奇怪的颜色,我从来没有设置过.检查状态显示FBO已成功创建.

https://github.com/glman74/simpleFBO

我已经查看了相关的stackoverflow问题,特别是datenwolf下面的链接,它显示了如何使用GLUT设置FBO,但不使用着色器.我仍然不确定我做错了什么.

https://github.com/datenwolf/codesamples/blob/master/samples/OpenGL/minimalfbo/

我还在这里附上代码的相关部分.在renderFBO方法中,我只是在做清楚.我原本期望在主渲染中渲染多边形时使用这种纯色(绿色)纹理.

FBO设置:

// intialize FBO
- (void)setupFBO
{
    fbo_width = 512;
    fbo_height = 512;

    glGenFramebuffers(1, &fboHandle);
    glGenTextures(1, &fboTex);
    glGenRenderbuffers(1, &depthBuffer);

    glBindFramebuffer(GL_FRAMEBUFFER, fboHandle);

    glBindTexture(GL_TEXTURE_2D, fboTex);
    glTexImage2D( GL_TEXTURE_2D,
                 0,
                 GL_RGBA,
                 fbo_width, fbo_height,
                 0,
                 GL_RGBA,
                 GL_UNSIGNED_BYTE,
                 NULL);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER_APPLE, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fboTex, 0);

    glBindRenderbuffer(GL_RENDERBUFFER, depthBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24_OES, fbo_width, fbo_height);
    glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER_APPLE, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBuffer);

    // FBO status check
    GLenum status;
    status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    switch(status) {
        case GL_FRAMEBUFFER_COMPLETE:
            NSLog(@"fbo complete");
            break;

        case GL_FRAMEBUFFER_UNSUPPORTED:
            NSLog(@"fbo unsupported");
            break;

        default:
            /* programming error; will fail on all hardware */
            NSLog(@"Framebuffer Error");
            break;
    }

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

FBO渲染:

// render FBO 
- (void)renderFBO
{
    glBindTexture(GL_TEXTURE_2D, 0);
    glEnable(GL_TEXTURE_2D);
    glBindFramebuffer(GL_FRAMEBUFFER, fboHandle);

    glViewport(0,0, fbo_width, fbo_height);
    glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

主要渲染:

- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
    // render FBO tex
    [self renderFBO];

    glViewport(0, 0, self.view.bounds.size.width, self.view.bounds.size.height);
    // render main
    glClearColor(0.65f, 0.65f, 0.65f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_TEXTURE_2D);
    glActiveTexture(GL_TEXTURE0);

    glUniform1i(uSamplerLoc, 0);     
    // Render 
    glUseProgram(_program);

    glUniformMatrix4fv(uniforms[UNIFORM_MODELVIEWPROJECTION_MATRIX], 1, 0, _modelViewProjectionMatrix.m);
    glUniformMatrix3fv(uniforms[UNIFORM_NORMAL_MATRIX], 1, 0, _normalMatrix.m);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    glDisable(GL_TEXTURE_2D);
}

关于我可能做错了什么的想法？

编辑#1:

我在github上对代码做了一些小改动.尝试使用GL_FRAMEBUFFER而不是上面的GL_DRAW_FRAMEBUFFER_APPLE.还添加了一个缺少绑定纹理调用.仍然无法正常工作.

编辑#2:

我找到了解决方案.我需要调用main渲染:

// reset to main framebuffer
[((GLKView *) self.view) bindDrawable];    

Answer 1

找到了解决方案,我已经更新了下面的代码,以防它对某人有用.

https://github.com/glman74/simpleFBO/

主要问题是我需要调用main渲染:

// reset to main framebuffer
[((GLKView *) self.view) bindDrawable];   

这是因为我使用的是GLKView.情况与CAEAGLLayer示例不同.