How to debug default frame and depth buffers? - c++

Question

I'm trying to implement shadows on my custom renderer through dynamic shadow mapping and forward rendering (deferred rendering will be implemented later). For instance, everything renders correctly to the Framebuffer used to generate the shadow map. However, when using the default Framebuffer to render the scene normally only the skybox gets rendered (it means that the default Framebuffer is used) and my only hypothesis is that the problem is related with the depth buffer since disabling the call to DrawActors(...) (in ForwardRenderShadows) appears to solve the problem but I can't generate my depth map if doing so. Any suggestions on the matter?
Code:
void Scene::DrawActors(const graphics::Shader& shader)
{
for(const auto& actor : actors_)
actor->Draw(shader);
}
template <typename T>
void ForwardRenderShadows(const graphics::Shader& shadow_shader, const std::vector<T>& lights)
{
for(const auto& light : lights)
{
if(light->Shadow())
{
light->DrawShadows(shadow_shader);
DrawActors(shadow_shader); //removing this line "solves the problem"
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
}
}
/*
shadow mapping is only implemented on directional lights for the moment, and that is the
relevant code that gets called when the process starts, more code details at the end of code
snippet.
*/
void DirectionalLight::SetupShadows()
{
glGenFramebuffers(1, &framebuffer_);
glGenTextures(1, &shadow_map_);
glBindTexture(GL_TEXTURE_2D, shadow_map_);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, constants::SHADOW_WIDTH, constants::SHADOW_HEIGHT, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer_);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, shadow_map_, 0);
glDrawBuffer(GL_NONE);
glReadBuffer(GL_NONE);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
throw std::runtime_error("Directional light framebuffer is not complete \n");
glBindFramebuffer(GL_FRAMEBUFFER, 0);
ShadowSetup(true);
}
void DirectionalLight::DrawShadows(const graphics::Shader& shader)
{
if(!ShadowSetup())
SetupShadows();
glViewport(0, 0, constants::SHADOW_WIDTH, constants::SHADOW_HEIGHT);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer_);
glClear(GL_DEPTH_BUFFER_BIT);
shader.Use();
projection_ = clutch::Orthopraphic(-10.0f, 10.0f, -10.0f, 10.0f, 1.0f, 100.0f);
transform_ = clutch::LookAt(direction_ * -1.0f, {0.0f, 0.0f, 0.0f, 0.0f}, {0.0f, 1.0f, 0.0f, 0.0f});
shader.SetUniformMat4("light_transform", projection_ * transform_);
}
void DirectionalLight::Draw(const graphics::Shader& shader)
{
shader.SetUniform4f("light_dir", direction_);
shader.SetUniform4f("light_color", color_);
shader.SetUniformMat4("light_transform", transform_);
shader.SetUniformMat4("light_projection", projection_);
shader.SetUniformInt("cast_shadow", shadows_);
glActiveTexture(GL_TEXTURE12);
shader.SetUniformInt("shadow_map", 12);
glBindTexture(GL_TEXTURE_2D, shadow_map_);
}
Code the repo: https://github.com/rxwp5657/Nitro
Relevant Files for the problem:
include/core/scene.hpp
include/core/directional_light.hpp
include/core/light_shadow.hpp
include/core/directional_light.hpp
include/graphics/mesh.hpp
src/core/scene.cpp
src/core/directional_light.cpp
src/core/light_shadow.cpp
src/core/directional_light.cpp
src/graphics/mesh.cpp
Finally, what I have tried so far is:
Deactivating depth testing with glDepthMask(GL_FALSE) and glDisable(GL_DEPTH_TEST) //same problem.
Changing depth function to glDepthFunc(GL_ALWAYS); // No desired results;

Answer 1

If you have a NVIDIA graphics card, you could have a look a Nsight. You can capture a frame and view all occurred GL-calls.
Then, you can select an event, for instance the event 22 in my example, and inspect all textures, the color buffer, the depth buffer and the stencil buffer.
Furthermore, you can have a look on all GL-state parameters at one event.

Answer 2

Ok, after using apitrace I found out that the VBO changes when switching from a custom Framebuffer to the default one. Because of this, the solution to the problem is to set again the VBO after switching to the default frame buffer.
Based on the code of the project, the solution is calling the Setup function again after switching to the default Framebuffer.
Setup function of the Mesh class:
void Mesh::Setup(const Shader& shader)
{
glGenVertexArrays(1, &vao_);
glBindVertexArray(vao_);
glGenBuffers(1, &elementbuffer_);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer_);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices_.size() * sizeof(unsigned int), &indices_[0], GL_STATIC_DRAW);
glGenBuffers(1, &vbo_);
glBindBuffer(GL_ARRAY_BUFFER, vbo_);
glBufferData(GL_ARRAY_BUFFER, vertices_.size() * sizeof(Vertex), &vertices_[0], GL_STATIC_DRAW);
shader.PosAttrib("aPosition", 3, GL_FLOAT, sizeof(Vertex), 0);
shader.PosAttrib("aNormal", 3, GL_FLOAT, sizeof(Vertex), offsetof(Vertex, normal));
shader.PosAttrib("aTexCoord", 2, GL_FLOAT, sizeof(Vertex), offsetof(Vertex, tex_coord));
shader.PosAttrib("aTangent", 3, GL_FLOAT, sizeof(Vertex), offsetof(Vertex, tangent));
shader.PosAttrib("aBitangent",3, GL_FLOAT, sizeof(Vertex), offsetof(Vertex, bitangent));
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
loaded_ = true;
}
Vertices buffer after switching to default frame buffer
Vertices buffer with no Framebuffer switching (no shadow map generated)