使用glBlitFramebuffer显示纹理

我正在尝试实现一个简单的多遍渲染方案。我首先将场景的多采样版本blit到FBO beforeEffectsContext.fbo 。如果我随后将其blit到提供FB的应用程序,则工作正常。但我想在场景上进行另一个过程来模糊它 COLOR_ATTACHMENT0 在 beforeEffectsContext.fbo之前 ,对其进行采样,绘制一个四边形,并将模糊效果添加到另一个帧缓冲区 blurContext.fbo .

如果我知道显示的内容 blurContext.fbo 使用同样的方法,通过四元和纹理采样,将颜色附加到屏幕上,效果很好,我得到了一个模糊的场景。

但如果我尝试使用 glBlitFramebuffer() 相反,在这一步中,我得到了一个黑色的屏幕。问题似乎在于我对闪电战过程和FBO的误解。

的初始化代码 blurContext.fbo :

// BeforeEffects Framebuffer
glGenFramebuffers(1, &renderContext->beforeEffectsContext.fbo);
glBindFramebuffer(GL_FRAMEBUFFER, renderContext->beforeEffectsContext.fbo);

glGenTextures(1, &renderContext->beforeEffectsContext.colorAttachment);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, renderContext->beforeEffectsContext.colorAttachment);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 800, 600, 0, GL_RGBA, GL_FLOAT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderContext->beforeEffectsContext.colorAttachment, 0);

// Blur Framebuffer
glGenFramebuffers(1, &renderContext->blurContext.fbo);
glBindFramebuffer(GL_FRAMEBUFFER, renderContext->blurContext.fbo);

glGenTextures(1, &renderContext->blurContext.colorAttachment);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, renderContext->blurContext.colorAttachment);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 800, 600, 0, GL_RGBA, GL_FLOAT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderContext->blurContext.colorAttachment, 0);

致使:

// Draw to the MSampled scene to the BeforeEffects framebuffer
glBindFramebuffer(GL_READ_FRAMEBUFFER, renderContext->multiSamplingContext.fbo);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, renderContext->beforeEffectsContext.fbo);
glBlitFramebuffer(0, 0, 800, 600, 0, 0, 800, 600, GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST);

// Sample the texture attached to the beforeEffects FBO and draw to the blur FBO
glBindTexture(GL_TEXTURE_2D, renderContext->beforeEffectsContext.colorAttachment);
glBindFramebuffer(GL_FRAMEBUFFER, renderContext->blurContext.fbo);
glViewport(0, 0, 800, 600);

glUseProgram(renderContext->blurProgramContext.program);
glBindVertexArray(renderContext->vaoBlur);

glDrawArrays(GL_QUADS, 0, 4);

glUseProgram(0);
glBindVertexArray(0);

// Blit the content of the blur FBO to the app-provided Framebuffer (doesn't work, black screen)
glBindFramebuffer(GL_READ_FRAMEBUFFER, renderContext->blurContext.fbo);
glReadBuffer(GL_COLOR_ATTACHMENT0);
glBindFramebuffer(GL_DRAW_BUFFER, 0);
glViewport(0, 0, 800, 600);
glBlitFramebuffer(0, 0, 800, 600, 0, 0, 800, 600, GL_COLOR_BUFFER_BIT,
    GL_NEAREST);