FogCast

FogCast is an ultra-lightweight, self-hosted fog-of-war system built specifically to bring your digital battlemaps to life during in-person gaming sessions.

If you use a projector, a TV laid flat on the table, or a large digital display for your tabletop RPG campaigns, FogCast gives you total control over what your players can see—in real time.

Key Features

• Real-Time Fog of War: Effortlessly reveal or hide map areas on the fly. Your players only see what you want them to see.
• Intuitive DM Controls: Dynamically draw or erase fog using flexible brush or rectangle tools.
• Smooth Navigation: Zoom and pan across massive maps without losing your place.
• Tablet & Touch Friendly: Full support for pen styluses and finger-gestures, making it perfect for Game Masters who run their sessions from a tablet.
• Built for Low-Power Devices: The player view is highly optimized, meaning it runs flawlessly even on low-memory hardware like basic browsers or Android TV sticks plugged into a projector.

What FogCast Isn't

FogCast is not a fully-featured, complex Virtual Tabletop (VTT) with built-in character sheets, dice rollers, or chat windows.

DM View	Player View

My personal setup

• A server running a dockerized FogCast instance, exposed via Cloudflare tunnel.
• A android TV projector, running the player view in a browser. Projects map onto tabletop.
• A tablet running the DM view in a browser, connected to the same LAN.

This project was inspired by https://github.com/dungeon-revealer/dungeon-revealer, but that project is no longer maintained and I wanted a simpler, more lightweight solution that could run on a low-power device.

Self-Hosting With Container Image

The easiest way to self-host FogCast is to run the published container image.

Run published image from GHCR

docker run --name fogcast \
	-p 8080:8080 \
	-v fogcast-data:/data \
	ghcr.io/dereknola/fogcast:latest

Open:

• http://localhost:8080/dm
• http://localhost:8080/player

Container configuration

These defaults are container-friendly out of the box:

• FOGCAST_ADDR=:8080
• FOGCAST_DATA_DIR=/data
• FOGCAST_STATIC_DIR=/app/static

You can override them by passing environment variables to docker run.

Building From Source

Run the build script from the repository root:

./scripts/build.sh

This will:

• install frontend dependencies for web/dm and web/player
• build both frontend apps
• build the Go server binary to bin/fogcast

Running And Connecting

Start the server from the repository root:

./bin/fogcast

By default, FogCast listens on port 8080.

• On the same machine:
  • http://localhost:8080
• DM controls:
  • http://localhost:8080/dm
• Player display:
  • http://localhost:8080/player

To connect from another device on your local network, replace localhost with the host machine's LAN IP, for example:

• http://192.168.1.25:8080/dm
• http://192.168.1.25:8080/player

Testing And CI

FogCast uses a browser E2E memory gate test for quality checks.

• starts the server
• uploads the large map (Goblin Lair)
• opens the Player view in Chromium and samples browser memory
• uploads the small map (Town Neighborhood)
• samples browser memory again and enforces per-map thresholds

Running E2E Memory Test Locally

Install dependencies once:

npm ci
npx playwright install chromium

Run the E2E memory test:

npm run test:e2e:memory

Threshold env vars:

• FOGCAST_E2E_GOBLIN_MAX_MB=140
• FOGCAST_E2E_TOWN_MAX_MB=120
• FOGCAST_E2E_SUMMARY_PATH=test-results/e2e-player-memory-summary.json

AI Usage

This project was designed and implemented with the assistance of AI. Gemini-3.5 was used for initial design and architecture, and ChatGPT-5.3-Codex was used for code generation and refactoring. All code was reviewed and tested by a human developer (me) before being committed to the repository.

Test Map Attribution (CC BY 4.0)

Some test map assets included in this repository are from Elven Tower Adventures:

• Creator: Elven Tower Adventures
• License: Creative Commons Attribution 4.0 International (CC BY 4.0)
  • https://creativecommons.org/licenses/by/4.0/

These assets are used only for testing and development purposes in FogCast.