ImGui editor: scene inspection and debug tools

Prisma Engine ships with an integrated ImGui-based editor that sits on top of the Vulkan rendering backend. The editor renders its UI into a separate ImGui Vulkan pass that shares the GPU device with the engine’s main viewport. It is enabled automatically on debug builds and can be toggled at configure time with a single CMake flag.

How ImGui is integrated

The editor is a separate build target (src/editor/) that embeds the engine as a library. The Editor class owns an Engine instance, drives the main loop, and adds EditorLayer to the layer stack. EditorLayer implements OnImGuiRender(), which is called every frame between the engine’s render commands and Present.

Editor (master process)
  ├── Engine  (owned by Editor)
  │     └── RenderSystem → Vulkan backend
  └── EditorLayer : Layer
        ├── OnUpdate(ts)
        ├── OnRender()        — viewport render pass
        └── OnImGuiRender()   — scene inspector, component panel, overlays

ImGui resources (descriptor pool, sampler, viewport texture) are managed by ImGuiVulkanResourceManager. Viewport textures use a deferred deletion queue to avoid destroying GPU resources while they are still in flight.

Enabling the editor

PRISMA_ENABLE_IMGUI_DEBUG controls whether the ImGui UI is compiled in. It defaults to ON for debug configurations:

# Explicitly enable ImGui debug UI (already the default on debug builds)
-DPRISMA_ENABLE_IMGUI_DEBUG=ON

# Disable for a release engine build (no UI overhead)
-DPRISMA_ENABLE_IMGUI_DEBUG=OFF

PRISMA_ENABLE_IMGUI_DEBUG only controls the ImGui overlay built into engine debug builds. The full editor target (PRISMA_BUILD_EDITOR) is a separate flag and is ON by default on Windows.

Building the editor

Use the editor-{platform}-{arch}-{config} CMake presets. The editor preset automatically enables Vulkan and ImGui:

Windows
Linux

cmake --preset editor-windows-x64-debug
cmake --build --preset editor-windows-x64-debug

cmake --preset editor-windows-x64-release
cmake --build --preset editor-windows-x64-release

You can also open the PrismaEngine root folder in Visual Studio 2022 — it detects the CMake configuration automatically. Build with Ctrl+Shift+B.

cmake --preset editor-linux-x64-debug
cmake --build --preset editor-linux-x64-debug

# ARM64
cmake --preset editor-linux-arm64-debug
cmake --build --preset editor-linux-arm64-debug

Linux CMake presets are defined but not fully validated. Community testing is welcome. Report issues at the PrismaEngine GitHub repository.

Current editor features

The editor is under active development. The following panels are available:

Panel	Status	Description
Scene inspector	In progress (~30%)	Lists scene hierarchy; click to select a `GameObject`
Component panel	In progress (~30%)	Displays components on the selected entity
Viewport	Functional	Renders the engine scene into an ImGui image via Vulkan
Project settings	Functional	`ProjectSettingsWindow` — engine and platform configuration
ImGui demo window	Available	Toggle `m_showDemoWindow` in `Editor` for widget reference

The scene inspector and component panel are approximately 30% complete. Editing component values in the UI is not yet fully wired to the engine’s ECS. Use these panels for read-only inspection for now.

Editor architecture

Editor::Initialize()

Creates the SDL3 window, initializes the engine, sets up the ImGui Vulkan backend, and allocates the descriptor pool and sampler for viewport texture sampling.

Editor::Run()

Drives the main loop: polls SDL3 events via OnEvent, calls OnUpdate, then OnRender (engine scene), then OnImGuiRender (editor panels), and finally presents.

EditorLayer::OnImGuiRender()

Submits ImGui draw calls for the scene inspector, component panel, viewport image, and any active debug overlays. This is where you add new panels.

Editor::Shutdown()

Flushes the deferred deletion queue, destroys ImGui Vulkan resources, shuts down the engine, and destroys the SDL3 window.

Writing an editor extension

Use prisma_create_editor_extension() in your CMakeLists.txt to build a shared library that links against the editor target:

# In your extension's CMakeLists.txt
prisma_create_editor_extension(MyEditorExtension
    SOURCES
        src/MyPanel.cpp
        src/MyPanel.h
)

The function creates a shared library, sets C++20, links Editor, and exports EDITOR_EXTENSION_EXPORTS=1 so you can mark public symbols with __declspec(dllexport) / __attribute__((visibility("default"))) consistently. A minimal panel implementation:

#include "engine/core/Layer.h"
#include <imgui.h>

class MyPanel : public Prisma::Layer {
public:
    void OnImGuiRender() override {
        ImGui::Begin("My Panel");
        ImGui::Text("Hello from a custom editor extension.");
        ImGui::End();
    }
};

CMake options reference

Option	Default	Description
`PRISMA_BUILD_EDITOR`	`ON` (Windows)	Build the standalone editor target
`PRISMA_ENABLE_IMGUI_DEBUG`	`ON` (debug)	Embed ImGui overlay in engine debug builds

Get Started

Core Concepts

Engine Systems

Platform Guides

SDK & Integration

ImGui editor: scene inspection and debug tools

How ImGui is integrated

Enabling the editor

Building the editor

Current editor features

Editor architecture

Writing an editor extension

CMake options reference

​How ImGui is integrated

​Enabling the editor

​Building the editor

​Current editor features

​Editor architecture

​Writing an editor extension

​CMake options reference

How ImGui is integrated

Enabling the editor

Building the editor

Current editor features

Editor architecture

Writing an editor extension

CMake options reference