So... I am trying to filter an environment map for a BRDF shader, as explained here: https://learnopengl.com/PBR/IBL/Specular-IBL. However, I can't get my filtered result to be properly stored (when loaded, I get a black texture full of artifacts.)
I figure it must have something to do with the frame buffer, since glCheckFramebufferStatus() keeps returning 0 on the LOD/sides loop, but I have spent a couple hours trying to understand why... and I can't see the problem. glGetError() returns 0, I made sure to generate the frame buffer/ render/ buffer before the loop starts, and at that point everything seemed complete. The rest of the program runs fine, and there were no errors compiling the shader I am using.
I am quite new to openGL, is there something obvious I am missing? I am assuming the problem must be in this section... but does it look like it should work? Could it be something I did wrong elsewhere?
This is the code:
if (cubeMapGenerated == false){
//Frame Buffer:
glGenFramebuffers(1, &frameBuffer);
glGenRenderbuffers(1, &renderBuffer);
glGenTextures(1, &genCubeMap);
glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
glBindTexture(GL_TEXTURE_CUBE_MAP, genCubeMap);
for (unsigned int i = 0; i < 6; ++i)
{glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGBA16F, 128, 128, 0, GL_RGB, GL_FLOAT, nullptr);}
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); //params
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glGenerateMipmap(GL_TEXTURE_CUBE_MAP); //generate mipmaps
glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width_, height_);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
std::cout << "Framebuffer is not complete at gen. Staus: " << glCheckFramebufferStatus(GL_FRAMEBUFFER) << std::endl;
GLuint projection_location, view_location, model_location, normal_matrix_location,
specular_map_location, roughness_location;
cubeMapGen_program_->bind(); //bind irradiance sahder
projection_location = cubeMapGen_program_->uniformLocation("projection");
view_location = cubeMapGen_program_->uniformLocation("view");
model_location = cubeMapGen_program_->uniformLocation("model");
normal_matrix_location = cubeMapGen_program_->uniformLocation("normal_matrix");
specular_map_location = cubeMapGen_program_->uniformLocation("specular_map");
roughness_location =brdf_program_->uniformLocation("roughness");
glUniformMatrix4fv(projection_location, 1, GL_FALSE, e_captureProjection.data());
glUniformMatrix4fv(model_location, 1, GL_FALSE, model.data());
glUniformMatrix3fv(normal_matrix_location, 1, GL_FALSE, normal.data());
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_CUBE_MAP, specular_map_);
glUniform1i(specular_map_location, 0);
for (unsigned int mip = 0; mip < maxMipLevels; ++mip){//render each mip
// resize framebuffer according to mip-level size.
unsigned int mipWidth = 128 * std::pow(0.5, mip);
unsigned int mipHeight = 128 * std::pow(0.5, mip);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, mipWidth, mipHeight);
std::cout << "width: " << mipWidth << " height: " << mipHeight << std::endl;
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer);
glViewport(0, 0, mipWidth, mipHeight);
float mproughness = (float) mip / (float)(maxMipLevels - 1);
glUniform1f (roughness_location, mproughness);
for (unsigned int i = 0; i < 6; ++i)//render each side
{
glUniformMatrix4fv(view_location, 1, GL_FALSE, e_captureViews[i].data());
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, genCubeMap, mip);
if(i == 0 && glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{std::cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete! Map: " << mip << std::endl;}
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBegin(GL_TRIANGLES);
glVertex3f(2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, 2, 2); //Right
glVertex3f(2, -2, -2); glVertex3f(2, 2, 2); glVertex3f(2, 2, -2);
glVertex3f(-2, -2, -2); glVertex3f(-2, 2, 2); glVertex3f(-2, -2, 2); //Left
glVertex3f(-2, -2, -2); glVertex3f(-2, 2, -2); glVertex3f(-2, 2, 2);
glVertex3f(-2, -2, 2); glVertex3f(-2, 2, 2); glVertex3f(2, 2, 2); //Front
glVertex3f(-2, -2, 2); glVertex3f(2, 2, 2); glVertex3f(2, -2, 2);
glVertex3f(-2, -2, -2); glVertex3f(2, 2, -2); glVertex3f(-2, 2, -2); //Back
glVertex3f(-2, -2, -2); glVertex3f(2, -2, -2); glVertex3f(2, 2, -2);
glVertex3f(-2, 2, -2); glVertex3f(2, 2, -2); glVertex3f(2, 2, 2); //Top
glVertex3f(-2, 2, -2); glVertex3f(2, 2, 2); glVertex3f(-2, 2, 2);
glVertex3f(-2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, -2, -2); //Bottom
glVertex3f(-2, -2, -2); glVertex3f(-2, -2, 2); glVertex3f(2, -2, 2);
}
//std::cout << glGetError() << ", " << glCheckFramebufferStatus(GL_FRAMEBUFFER) << std::endl;
}
std::cout<<"New pre filtered map generated"<<std::endl;
cubeMapGenerated = true;
}//cubemapgen
glEnd();
I recommend to read about Vertex Specification and to use the state of the art way of Vertex Array Objects for drawing.
But, if you draw the objects in to deprecated Fixed Function Pipeline style, then geometric objects are drawn by enclosing a series of vertex coordinates between glBegin/glEnd pairs.
You have to finish the drawing sequence by glEnd, before you can change or manipulate the framebuffer.
Move the glEnd instruction in the inner loop and your code should work
for (unsigned int mip = 0; mip < maxMipLevels; ++mip)
{
.....
for (unsigned int i = 0; i < 6; ++i)//render each side
{
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, genCubeMap, mip);
glBegin(GL_TRIANGLES);
glVertex3f(2, -2, -2); glVertex3f(2, -2, 2); glVertex3f(2, 2, 2);
.....
glVertex3f(-2, -2, -2); glVertex3f(-2, -2, 2); glVertex3f(2, -2, 2);
glEnd(); // <---- "end" the draw sequence
}
}
See OpenGL 3.0 API Specification; 2.6.3 GL Commands within Begin/End; page 24
or OpenGL 4.6 API Compatibility Profile Specification; 10.7.5 Commands Allowed Between Begin and End; page 433:
The only GL commands that are allowed within any Begin/End pairs are the commands for specifying vertex coordinates, vertex colors, normal coordinates, texture coordinates, generic vertex attributes, and fog coordinates ...