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Advanced Fog of War

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This feature is the Advanced Version of the Fog of War tool that is available to Plus and Pro Roll20 Subscribers. If you want to know more about the Fog of War Features that are available to all Roll20 users, please go here.

Advanced Fog of War
The Advanced Fog of War feature clears fog away dynamically as a token moves across the Page and the Fog of each player's view will only be revealed by the tokens they have control over. Similar to how a battle map is revealed in a real-time strategy computer game, the area that the token moves out of, remains revealed to the players in desaturated colors until they return. Monster and NPC tokens that are not in the player's token's current area of play will not be visible, even if they are present in the previously revealed areas of the Page. This allows you to reveal an ever expanding maze of a dungeon to the party, room by room, while they explore without having to manually clear the fog away for them. This feature can also be used in combination with Dynamic Lighting to block line of sight along dungeon walls and other obstructions.


How it Works

With Standard Fog of War, fog is drawn over the entire Page and the GM must trace areas utilizing the drawing tools from the Fog of War subtools of the Tabletop Toolbox to reveal areas for Players to see through to the Tabletop. This experience can be cumbersome to manually reveal complex interior environments and you can't tailor the view for each individual player in the game.

When enabled, Advanced Fog of War assists with these two issues by having the tokens that emit light, or have a set view distance, clear fog dynamically as they're moved across the Page. The Fog divides itself up into a series of square cells that follow the grid set by your Page Settings (or the Scale you set for your Page when gridless). As a token moves across the playspace, the Advanced Fog of War calculates which cells the token has passed through and keeps them revealed on the Page. Tokens on the Object and Tokens Layer that are in this revealed area but NOT in range of the token currently are hidden from view to the Player as if they were on the GM Layer.

The fog cells that a token has revealed is saved for each token on a Page, so each player potentially can have a unique view of the same Page they are all currently exploring.

Enabling Advanced Fog of War

To enable Advanced Fog of War, go to the Page Settings dialog of the page you wish to enable it on. Beneath the Standard Fog of War checkbox is a section for the Advanced Fog of War features.

The Advanced Fog of War Section of the Page Settings

AFoW Page Settings.png

There are four Advanced Fog of War settings that can be managed from the Page Settings:

  1. Enabled Checkbox: The Enabled checkbox will turn Advanced Fog of War on for the page when checked.
  2. The Size Input Field: The Size number input field is only visible if the Page Settings has the Grid currently disabled. Advanced Fog of War requires a grid to calculate which areas of the Page are hidden or revealed. With the Grid turned off on a Page, this setting will allow you to dictate how large the square cells are that are revealed when the token is moved across the Page. At default, this field is set to 1 unit and utilizes the Scale you're using at the top of the Page Settings dialog box.
  3. Show Grid Checkbox: The Show Grid checkbox is a feature tied to Dynamic Lighting. When Dynamic Lighting is enabled on the page, the grid lines will be hidden over areas not within a token's line of sight even if those area of the Page has been revealed from the Fog. Enabling Show Grid checkbox will make the grid visible over all revealed areas of the Page. The grid used for the Advanced Fog of War in this scenario is purely for calculating the Fog of War, it will not generate a visible grid on your gridless Page.
  4. Dim Light Reveals Checkbox: By default, if a Token has a light setting established on the token's Advanced Token Settings, it will reveal an area that is only in "bright" light. It will ignore the larger radius that is cast in "Dim" light if available on the Token Settings. The Dim Light Reveals checkbox, once checked, forces the boundary of the reveal to include both bright and dim light cast by the Token.

Setting Up Your Tokens

Now that Advanced Fog of War is enabled, you may need to adjust the Token Settings of the Tokens on the Page in order for them to reveal the advanced fog from the Tabletop.

Token Settings

The Dynamic Light and Advanced Fog of War section of the Advanced Token Settings

The Advanced Fog of War utilizes both the Emit Light settings that is used for Dynamic Lighting as well as a View Distance setting that is available exclusively for Advanced Fog of War. To access the Token Settings, double click on the desired token or click on the gear icon from the Token HUD UI when the token is currently selected. This will bring up the token's Token Settings dialog box. Click on the Advanced tab. You can either input values under Emits Light or the View Distance value to control fog reveal. If you enter a value for Dim Light, this will not have an affect on the area revealed UNLESS you have it enabled in the Page Settings discussed earlier. Any value entered in the View Distance under the Advanced Fog of War section will supercede any value you have in Emits Light.

The token must be controlled by a player in order for the token's reveal of the Fog to be visible to them. You can set this manually from the Token Settings (Basic Tab) or have it directed to the player who has edit permission of of the character journal the token represents. Each player's view of the fog is unique and depends on which tokens they have control of on the Tabletop.

Gameplay with Advanced Fog of War

Once your tokens settings are set in the way you want them, there's not much maintenance you will need to do as the GM during actual gameplay.

Revealing and Reapplying Fog

If you want to manually reveal/hide areas, you can use the same Fog of War subtools from the Tabletop Toolbox. Reveal Areas, Polygon Reveal, Hide Areas, and Reset Fog are all available to you. If you choose to reset the fog or manually hide areas, the areas within the Token's set sight or vision range can not be hidden from view. If you want to keep an area hidden even from the Token's range of sight, you'll want to use both versions of Fog of War at the same time.

Running with Both Fog of War and Advanced Fog of War Simultaneously

Fog of War and Advanced Fog of War are each their own individual layers of fog. You can use both versions at the same time to keep certain areas on the Page hidden from view even if a token with sight passes through it. Both versions use the same Toolbox subtools for revealing and hiding areas. If you use the tools while both are enabled, they hide or reveal on both layers at once; however, you can specifically edit the Fog of War or Advanced Fog of War individually by using the Reveal Areas, Polygon Reveal, and Hide Areas drawing tools while holding down the following shortcut keys:

  • Alt Key: Modify only Fog of War's fog layer
  • Ctrl Key: Modify only Advanced Fog of War's fog layer

Viewing A Singular Token's View of the Tabletop

As the GM, you will see each token's revealed path of the fog layer. At a glance, it may be difficult to know which player's tokens have uncovered which areas of the Advanced Fog of War. While holding down the shortcut key Ctrl/⌘ + L, select one of your tokens and your view of the tabletop will be isolated to that token's current view of the fog layer.

Feature Limitations

Advanced Fog of War, bundled together with Fog of War and Dynamic Lighting, brings a whole new level of interactive map exploration. There are some caveats to be aware of when using Advanced Fog of War.

Fog Reset Affects All Tokens

There is no way to reset the view of a single token. If a single player has treated their token as a fog a flashlight to reveal the entire page, using the Reset Fog tool will reset all of your player's views of the Page. You can prevent unintended reviews in a couple of ways. You can enable Fog of War alongside Advanced Fog of War and manually cover up areas of the Page that are spoiler-potential. Another method is by controlling token movement via the Restrict Movement feature of [Dynamic Lighting]. This option will corral player tokens within the boundaries drawn on the Dynamic Lighting layer.


Advanced Fog of War relies on a grid system, so the token's revealed path across a Page is represented by a series of grid cells cleared of fog. It can't reveal or hide partial areas of a grid cell. The cell is entirely visible or entirely hidden. This can run into issues if you have very narrow walled off areas on your Dynamic Lighting or wall outlines that aren't aligned to a grid. You may get unintentional reveals of secret doors or corridors. We recommend enabling both fog of war systems to help prevent this from happening, by manually adding fog to areas not meant to be seen on the other side of a Dynamic Lighting wall.

Processing Power

Like Dynamic Lighting, care needs to be taken so that you don't create too much lag for you and your players while using the Advanced Fog of War system. Each individual token that is emitting light or has an Advanced Fog of War vision set on it will have its view of the Page recorded to your game's data. If you have a lot of tokens on a Page set to interact with Advanced Fog of War, this may impact performance. You may want to minimize how many tokens are able to reveal Advanced Fog of War to only those that the Players are using, or only using one NPC token per monster group that reveals the terrain for them.

Page Size Cap

One measure we've made to help avoid performance lag by Advanced Fog of War is implementing a cell cap to the grid being used for the Advanced Fog of War. If you go over the maximum number of cells in the Page Settings, a warning message will appear that you are over the limit.