Why there is no output to the framebuffer's textures? - opengl

Question

Here is the code:
int main(){
//init gl environment
//...
//create textures for pass 1
GLuint normal_color_output;
glCreateTextures(GL_TEXTURE_2D_MULTISAMPLE, 1, &normal_color_output);
glTextureStorage2DMultisample(normal_color_output, 8, GL_RGBA32F, 1000, 800, GL_TRUE);
GLuint high_color_output;
glCreateTextures(GL_TEXTURE_2D_MULTISAMPLE, 1, &high_color_output);
glTextureStorage2DMultisample(high_color_output,8, GL_R11F_G11F_B10F, 1000, 800,GL_TRUE);
//init framebuffer
GLuint render_buffer;
glCreateRenderbuffers(1, &render_buffer);
glNamedRenderbufferStorageMultisample(render_buffer, 8, GL_DEPTH24_STENCIL8, 1000, 800);
GLuint framebuffer;
glCreateFramebuffers(1, &framebuffer);
glNamedFramebufferTexture(framebuffer, GL_COLOR_ATTACHMENT0, normal_color_output,0);
glNamedFramebufferTexture(framebuffer, GL_COLOR_ATTACHMENT1, high_color_output, 0);
glNamedFramebufferRenderbuffer(framebuffer, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, render_buffer);
const GLenum drawbuffers[] = {GL_COLOR_ATTACHMENT0,GL_COLOR_ATTACHMENT1};
glNamedFramebufferDrawBuffers(framebuffer, 2, drawbuffers);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
//init another framebuffer
//What I want to do is trying to achieve implementing my own msaa color resolve solution.
GLuint mix_framebuffer;
glCreateFramebuffers(1, &mix_framebuffer);
GLuint mix_renderbuffer;
glCreateRenderbuffers(1, &mix_renderbuffer);
glNamedRenderbufferStorage(mix_renderbuffer, GL_DEPTH24_STENCIL8, 1000, 800);
GLuint normal_antialiasing_texture, hdr_antialiasing_texture;
glCreateTextures(GL_TEXTURE_2D, 1, &normal_antialiasing_texture);
glTextureStorage2D(normal_antialiasing_texture, 1, GL_RGBA32F, 1000, 800);
glCreateTextures(GL_TEXTURE_2D, 1, &hdr_antialiasing_texture);
glTextureStorage2D(hdr_antialiasing_texture, 1, GL_RGBA32F, 1000, 800);
glNamedFramebufferTexture(mix_framebuffer, GL_COLOR_ATTACHMENT0, normal_antialiasing_texture, 0);
glNamedFramebufferTexture(mix_framebuffer, GL_COLOR_ATTACHMENT1, hdr_antialiasing_texture, 0);
glNamedFramebufferDrawBuffers(mix_framebuffer,2, drawbuffers);
glNamedFramebufferRenderbuffer(mix_framebuffer, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, mix_renderbuffer);
glBindFramebuffer(GL_FRAMEBUFFER, mix_framebuffer);
//....
//draw commands
while (!glfwWindowShouldClose(window)) {
// pass 1
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glUseProgram(program);
glUniformMatrix4fv(3, 1, GL_FALSE, glm::value_ptr(camera.GetViewMat()));
model.Render(program);
glPointSize(20.f);
glUseProgram(light_shader);// I draw a point to show the light's position
glUniformMatrix4fv(0, 1, GL_FALSE, glm::value_ptr(camera.GetViewMat()));
glDrawArrays(GL_POINTS, 0, 1);
//pass 2
glBindFramebuffer(GL_FRAMEBUFFER, mix_framebuffer);
glUseProgram(mix_program);
glBindTextureUnit(0, normal_color_output);
glBindTextureUnit(1, high_color_output);
glClear(GL_COLOR_BUFFER_BIT);
glNamedFramebufferDrawBuffers(mix_framebuffer, 2, drawbuffers);
glDrawArrays(GL_POINTS, 0, 1);
//...
}
}
I use geometry shader to model a square, here is the code:
//mix_gs.glsl
#version 450 core
layout(points) in;
layout(triangle_strip) out;
layout(max_vertices = 4) out;
void main(){
gl_Position = vec4(-1,1,-1,1);
EmitVertex();
gl_Position = vec4(-1,-1,-1,1);
EmitVertex();
gl_Position = vec4(1,1,-1,1);
EmitVertex();
gl_Position = vec4(1,-1,-1,1);
EmitVertex();
EndPrimitive();
}
here is the mix_fs.glsl:
#version 450 core
layout(location = 0)out vec4 color;
layout(location = 1)out vec4 hdr_color;
layout(binding = 0) uniform sampler2DMS color_sdms;
layout(binding = 1) uniform sampler2DMS hdr_sdms;
void main(){
/*
for(int i=0;i<8;i++){
color += texelFetch(color_sdms,ivec2(gl_FragCoord.xy),i);
hdr_color += vec4(texelFetch(hdr_sdms,ivec2(gl_FragCoord.xy),i).xyz,1);
}
*/
color = vec4(1,0,0,1);//I just output a color
hdr_color = vec4(0,1,0,1);
}
I encount a problem that I find during the draw pass 2, gl cannot outout any color to textures bind to mix_framebuffer.
Here is the debugging info in RenderDoc:
draw pass 1 texture output:
draw pass 2's geometry output:
draw pass 2 texture input:
draw pass 2 texture output:
You can see, draw-pass 1's output was passed to draw-pass2's pipeline successfully, but there is no output to draw-pass2's textures. I don't know why.

Answer 1

If you don't see even the plain color, the first I'd recommend to check how it was discarded. There are no so many options:
glColorMask. Highly likely it's not your case, since pass 1 works;
Wrong face culling and polygon winding order (CW, CCW). By your geometry shader, it looks like CW;
Blending options;
Depth-stencil state. I see you use glNamedRenderbufferStorage(mix_renderbuffer, GL_DEPTH24_STENCIL8, 1000, 800); What are depth-stencil settings?
If everything above looks good, any glGetError messages? If it's ok, try to remove MRT for a debugging purposes and output the only color in the second pass. If it would work, probably some error in MRT + Depth buffer setup.