Hi all.

I'm trying to combine forward rendering with my deferred renderer. My current approach is using glBlitFramebuffer to copy the depth buffer from G-buffer to another HDR fbo. However the blit function doesn't seem to work in my renderer. Gbuffer's depth buffer works well.

My G-buffer init code

        GLuint gBuffer;
	glGenFramebuffers(1, &gBuffer);
	glBindFramebuffer(GL_FRAMEBUFFER, gBuffer);
	GLuint gPosition, gNormal, gAlbedoSpec;
	// gbuffer: position
	glGenTextures(1, &gPosition);
	glBindTexture(GL_TEXTURE_2D, gPosition);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB16F, screenWidth, screenHeight, 0, GL_RGB, GL_FLOAT, NULL);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, gPosition, 0);
	// gbuffer:normal+roughness
	glGenTextures(1, &gNormal);
	glBindTexture(GL_TEXTURE_2D, gNormal);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, screenWidth, screenHeight, 0, GL_RGBA, GL_FLOAT, NULL);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, gNormal, 0);
	// gbuffer:albedo+specular
	glGenTextures(1, &gAlbedoSpec);
	glBindTexture(GL_TEXTURE_2D, gAlbedoSpec);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, screenWidth, screenHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, gAlbedoSpec, 0);
	GLuint attachments[3] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2 };
	glDrawBuffers(3, attachments);
//gbuffer depth
	GLuint gDepth;
	glGenRenderbuffers(1, &gDepth);
	glBindRenderbuffer(GL_RENDERBUFFER, gDepth);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, screenWidth, screenHeight);
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, gDepth)

HDR fbo init code:

        GLuint hdrFBO;
	glGenFramebuffers(1, &hdrFBO);
	glBindFramebuffer(GL_FRAMEBUFFER, hdrFBO);
//floating point color buffer for HDR
	GLuint colorBuffer;
	glGenTextures(1, &colorBuffer);
	glBindTexture(GL_TEXTURE_2D, colorBuffer);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, screenWidth, screenHeight, 0, GL_RGBA, GL_FLOAT, NULL);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, colorBuffer, 0);
//Attach depth render buffer to HDR fbo
	GLuint hdrDepth;
	glGenRenderbuffers(1, &hdrDepth);
	glBindRenderbuffer(GL_RENDERBUFFER, hdrDepth);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, screenWidth, screenHeight);
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, hdrDepth);

Blit function call:

//clear HDR fbo
        glBindFramebuffer(GL_FRAMEBUFFER, hdrFBO);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

//copy depth to hdr fbo
	glBindFramebuffer(GL_READ_FRAMEBUFFER, gBuffer);
	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, hdrFBO);
	glBlitFramebuffer(0, 0, screenWidth, screenHeight, 0, 0, screenWidth, screenHeight, GL_DEPTH_BUFFER_BIT, GL_NEAREST);
	glBindFramebuffer(GL_FRAMEBUFFER, hdrFBO);

//...then apply lighting pass of deferred shading, forward rendering and post-processing effect to the HDR fbo 

Any help would be appreciated.

Does anyone know if there's alternative way to combine forward shading with deferred shading?