ImGui Dockspace not working when viewports are enabled

[Platforming-Mayhem]

Version/Branch of Dear ImGui:

Branch: docking

Back-ends:

imgui_impl_glfw.cpp
imgui_impl_opengl3.cpp

Compiler, OS:

Windows 10

Full config/build information:

No response

Details:

I'm setting up imgui docking and multi-viewports, I'm trying to create a viewport window that renders my game's graphics in an imgui window. However when I use:

if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
{
ImGui::DockSpaceOverViewport();
}

it causes my render textures to clear and erase themselves so nothing gets rendered to screen or the viewport.

Screenshots/Video:

with ImGui::Dockspace

without ImGui::Dockspace

Minimal, Complete and Verifiable Example code:

ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();

if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
{
ImGui::DockSpaceOverViewport();
}

ImGui::Render();
glClear(GL_COLOR_BUFFER_BIT);
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
{
GLFWwindow* backup_current_context = glfwGetCurrentContext();
ImGui::UpdatePlatformWindows();
ImGui::RenderPlatformWindowsDefault();
glfwMakeContextCurrent(backup_current_context);
}

[PathogenDavid]

This is most likely an issue on your end. You should use a graphics debugger like RenderDoc to investigate.

[Platforming-Mayhem]

@PathogenDavid Why does it start working as soon as I disable ImGui::DockSpaceOverViewport();?

[PathogenDavid]

Hard to say without debugging your app, which is why I recommended looking at a graphics debugger.

[Platforming-Mayhem]

For some reason the vs output changes depending on whether dockspace is active or not. If it is active, gl_position goes to NaN. If it is inactive, the values are correct.
No Dockspace

Dockspace

[Platforming-Mayhem]

It seems like my program doesn't allow:
if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
{
GLFWwindow* backup_current_context = glfwGetCurrentContext();
ImGui::UpdatePlatformWindows();
ImGui::RenderPlatformWindowsDefault();
glfwMakeContextCurrent(backup_current_context);
}
and:
if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DockingEnable)
{
ImGui::DockSpaceOverViewport();
}
to run at the same time for some reason.

[ocornut]

It's possibly an issue in your code and you may be not sharing the relevant code.
It's ambiguous what those vertices you posted are (vertices for what?).
Try to confirm if your render-to-texture is valid in both cases.
Use Metrics/Debugger to inspect our draw calls.

[Platforming-Mayhem]

My textures are valid, it seems like my vertex positions become invalid. I'm not sure what is causing it to become invalid.

this is my vertex shader if it helps.

[ocornut]

it seems like my vertex positions become invalid.

OpenGL uses a bunch of global state, so it is possible that some of the state we alter inside ImGui_ImplOpenGL3_RenderDrawData() are altering your render because it doesn't explicitly set them up.

[ocornut]

My textures are valid, it seems like my vertex positions become invalid. I'm not sure what is causing it to become invalid.

Again, this can means different things and is very ambiguous to read without code. We still don't know how you are rendering the things that breaks.

If you have a texture working, then you can submit your framebuffer using ImGui::Image(), and then I don't understand what this shader is about because you shouldn't need one. So it seems like you are may doing something else but I cannot guess what it is.

I also don't know if by texture you are referring to the texture used as part of the render toward generating your framebuffer-rendered-to-texture, or if you are talking about your framebuffer-rendered-to-texture. Without code we can only guess.

[Platforming-Mayhem]

Through testing a bunch I've found out that my model matrix is getting screwed up for some reason. Also just to give some context, I am using ImGui to display a render texture using ImGui::Image. However the part that is going wrong happens during the rendering of the render texture, and the render texture is rendering a scene that contains a gameObject with a texture that looks like this:

The GameObject's texture is being passed correctly, but the render texture isn't rendering anything.

void K::Transform::PassModelMatrix(K::Transform* parent) 
{
	K::Matrix4x4 globalModelMatrix = K::Matrix4x4::IdentityMatrix();

	if (parent == nullptr)
	{
		//World space transforms are in control
		*this->localScale = *this->scale;
		*this->localRotation = *this->rotation;
		*this->localPosition = *this->position;
		//Scaling Matrix
		globalModelMatrix.m[0][0] *= this->scale->x;
		globalModelMatrix.m[1][1] *= this->scale->y;
		globalModelMatrix.m[2][2] *= this->scale->z;
		//Rotation Matrix
		globalModelMatrix = K::Matrix4x4::Matrix_MultiplyMatrix(globalModelMatrix, *K::Quaternion::Euler(this->rotation)->QuaternionToMatrix());
		//Translation Matrix
		globalModelMatrix.m[3][0] += this->position->x;
		globalModelMatrix.m[3][1] += this->position->y;
		globalModelMatrix.m[3][2] += this->position->z;
	}
	else
	{
		if (*this->position != this->previousPosition)
		{
			*this->localPosition = *this->position;
			K::Matrix4x4 invert = K::QuickInverse(parent->modelMatrix);
			K::MultiplyMatrixVector(*this->position, *this->localPosition, invert);
		}
		if (*this->rotation != this->previousRotation)
		{
			*this->localRotation = *this->rotation - *parent->rotation;
		}
		if (*this->scale != this->previousScale)
		{
			*this->localScale = *this->scale / *parent->scale;
		}

		//Local space transforms are in control
		*this->scale = *this->localScale * *parent->scale;
		*this->rotation = *this->localRotation + *parent->rotation;
		K::MultiplyMatrixVector(*this->localPosition, *this->position, parent->modelMatrix);
		//Scaling Matrix
		globalModelMatrix.m[0][0] *= this->scale->x;
		globalModelMatrix.m[1][1] *= this->scale->y;
		globalModelMatrix.m[2][2] *= this->scale->z;
		//Rotation Matrix
		globalModelMatrix = K::Matrix4x4::Matrix_MultiplyMatrix(globalModelMatrix, *K::Quaternion::Euler(this->rotation)->QuaternionToMatrix());
		//Translation Matrix
		globalModelMatrix.m[3][0] += this->position->x;
		globalModelMatrix.m[3][1] += this->position->y;
		globalModelMatrix.m[3][2] += this->position->z;
	}

	this->modelMatrix = globalModelMatrix;

	this->previousPosition = *this->position;
	this->previousRotation = *this->rotation;
	this->previousScale = *this->scale;
}

This is the code(^) used to construct the model matrix, this->modelMatrix is the final model matrix that gets passed to the shader.

void GameObject::PassTransformationMatrix()
{
	if (this->parent == nullptr) 
		this->GetTransform()->PassModelMatrix();
	else 
		this->GetTransform()->PassModelMatrix(this->parent->GetTransform());
	glUniformMatrix4fv(glGetUniformLocation(this->material->GetShader()->shader, "modelMatrix"), 1, GL_FALSE, &this->GetTransform()->modelMatrix.m[0][0]);
}

[Platforming-Mayhem]

I managed to fix the issue, it was an issue with how I setup my rotation Matrix and how it was applying to the model matrix. It ended up exploding everything. Thanks for helping me, even though it wasn't an issue with your codebase :)