Fog Weaver
A Foundry VTT v13+ module that gives the GM full manual control over fog of war. When enabled, token movement no longer reveals fog — the GM paints revealed and hidden areas directly using a set of drawing tools.
Requirements
- Foundry VTT v13+
- [libWrapper](https://foundryvtt.com/packages/lib-wrapper) v1.12+
Features
- Four drawing tools: Circle/Ellipse, Rectangle, Line, and Freehand
- Alt + drag on any tool switches to erase mode (re-fogs the painted area)
- Shift + drag draws from center (circle and rectangle tools)
- Ctrl + drag constrains to a perfect circle or square (circle and rectangle tools)
- Single click with the Freehand tool deposits a dot at the click point
- In-HUD panel with live sliders for fog opacity, fog tint color, and line/stroke width
- Undo (Ctrl+Z or the Foundry undo keybind) removes the most recently drawn shape and rebuilds the fog texture
- Reset Fog button clears all revealed/hidden areas and the drawing history
Installation
Install using the manifest URL directly.
Usage
Activating the module
Enable the module in Module Management. The module adds an Enable Manual Fog Control world setting (on by default). When enabled, the Fog Weaver scene control (cloud-fog icon) appears in the left toolbar, visible only to GMs.
Click the Fog Weaver toolbar button to activate the layer. A HUD panel appears to the right of the toolbar with live controls.
Drawing tools
| Tool | Icon | Behavior |
| Circle/Ellipse | fa-circle | Drag to draw an ellipse from corner to corner |
| Rectangle | fa-square | Drag to draw a rectangle from corner to corner |
| Line | fa-minus | Drag to draw a stroked line |
| Freehand | fa-paintbrush | Drag to paint a freehand stroke; click for a dog |
Modifier keys
| Key | Effect |
| Alt | Erase mode - preview turns red; release to hide fog along the shape |
| Shift | Draw from center (circle and rectangle tools only) |
| Ctrl/Cmd | Constrain to circle or square aspect ratio (circle and rectangle tools only) |
Modifier keys can be pressed and released while dragging; the preview updates in real time.
HUD panel
The panel appears automatically when the Fog Weaver layer is active:
| Control | Description |
| Fog Opacity slider | How opaque unexplored fog appears to the GM while the tool is active (does not affect players) |
| Fog Tint color picker | Color of unexplored fog areas shown to the GM |
| Line Width slider | Stroke width used by the Line and Freehand tools (world units) |
These controls are per-client. Changes are saved to the module settings immediately on release.
Undo
Press Ctrl+Z (or the Foundry undo keybind) to remove the most recently drawn shape. The fog texture is rebuilt from the remaining shape history. Each undo step is a single shape record; multiple undos pop the stack one at a time.
Reset Fog
Click the Reset Fog button (cloud icon, bottom of the tool list) to erase all revealed and hidden areas and clear the entire drawing history. This operation cannot be undone.
Settings
| Setting | Scope | Default | Description |
| Enable Manual Fog Control | World | true | Master switch. When off, token movement resumes revealing fog normally. |
| Line Tool Width | World | 100 | Stroke width (world px) for the Line and Freehand tools. Range: 20–500. |
| GM Fog Preview Opacity | Client | 0.7 | Fog opacity shown to the GM while the Fog Weaver layer is active. Range: 0.2–1.0. |
| GM Fog Tint COlor | Client | #000000 | Color of unexplored fog shown to the GM. |
AI Usage
AI has been used to CSS styling and for researching the Foundry VTT APIs to ensure proper usage most especially for determine the differences between the various versions of Foundry supported by the module.