SeeRT Overlay

It's a Saturday afternoon, and you have the hankering to play a classic game from your childhood - Super Mario 64! You boot up the game on your PC and notice the characters look a little too "angular" for your nostalgia causing the experience lack some of the character from days gone by. No problem, I'll just switch on some classic anime instead! Oh, well the colors aren't as vibrant and it's missing that "glow"...

Wouldn't it be nice to view retro media in the format it was designed to be played/viewed in? Wouldn't it be nice to make your very nice 4k monitor wildly antiquated? Wouldn't it be nice for you monitor to still have scanlines and static to further distort your view?

Well me too! Enter - SeeRT!

A short forward...

I've been in my "better practice an agentic workflow within development to stay up with the times" arc, so this project was prompted probably 90% using Claude, me only tweaking a few things here and there and running a few commands when Claude seemed to get stuck.

What is it?

A Windows CRT monitor overlay that applies a real-time shader filter over any window or monitor. The filter runs in a transparent, click-through DirectComposition overlay — the target application sees no performance impact and requires no modification.

Before	After

(P.S. I didn't want to boot my emulator for this, but thanks to "packattack04082" on youtube for the gameplay I got my screenshots from!)

Features

Shader pipeline (RetroArch-inspired, gamma-correct)

• Barrel/pincushion distortion with zoom compensation
• Gaussian beam scanlines with luminance-dependent spread
• Shadow mask — aperture grille, shadow mask dots, and slot mask patterns (anti-aliased)
• Phosphor bloom and diffusion
• RGB convergence error (chromatic aberration)
• Vignette, hum bar, flicker, and TV static
• Phosphor tint (R/G/B) for monochrome terminal looks
• Colour grading — brightness, contrast, saturation

Overlay

• Captures any window or monitor via Windows Graphics Capture
• Click-through when settings panel is closed; receives input when open
• Multi-monitor: add secondary overlays to additional monitors
• Custom CRT cursor rendered inside the shader (barrel-distorted with the image)
• Shake mouse to reveal cursor and settings toggle button
• System tray icon

Settings

• ImGui settings panel with multiple UI themes
• 11 built-in presets + save/load/reorder user presets
• Settings persist to %APPDATA%\SeeRT Overlay\settings.json
• Audio loopback capture (optional)

Built-in Presets

Preset	Character
Default	Balanced starting point
Early 2000s Laptop	Subtle, LCD-era hint of CRT
Arcade	Bold cabinet look — heavy scanlines, strong mask
Green Phosphor	P31 monochrome terminal
Amber Phosphor	P3 amber/orange terminal
Heavy CRT	Degraded 1980s boxy TV
crt-geom	Classic RetroArch reference implementation
crt-lottes	Tim Lottes' shader — crisp, fine slot mask
Sony PVM	Professional reference monitor, minimal artifacts
Trinitron	Flat aperture-grille tube, SNES/PS1 era
NTSC Composite	Degraded consumer signal with convergence error

Requirements

• Windows 10 or later
• Visual Studio 2022+ Build Tools with the Desktop development with C++ workload
• Windows SDK 10.0.26100+
• vcpkg installed and available (e.g. C:/vcpkg)

Building

1. Clone the repo and open a terminal in the project root.

2. If vcpkg is not at C:/vcpkg, edit CMakePresets.json and update toolchainFile to point to your vcpkg installation.

3. Configure and build:

   cmake --preset default
   cmake --build --preset default

4. The executable is at build/bin/Release/SeeRT Overlay.exe. Shader .cso files and font assets are copied next to it automatically.

Dependencies (imgui, nlohmann-json) are installed automatically from vcpkg.json during the configure step — no manual vcpkg install needed.

Tech Stack

Layer	Technology
Language	C++20
Renderer	Direct3D 11
Shaders	HLSL 5.0 (compiled via fxc.exe)
Screen capture	Windows Graphics Capture (C++/WinRT)
UI	Dear ImGui
Composition	DirectComposition
JSON	nlohmann/json
Package manager	vcpkg (manifest mode)