Dynamic Lighting

This page is about Dynamic Lighting, a feature exclusive to Plus and Pro subscribers, or to players in a game created by a subscriber. If you'd like to use this feature, consider upgrading your account

This feature calculates line of sight on the fly as tokens are moved across the tabletop.

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Dynamic Lighting / Line of Sight  

The Dynamic Lighting Layer

In addition to the Map & Background Layer, the Object & Token Layer, and the GM Overlay Layer is the Dynamic Lighting Layer. This fourth layer’s purpose is for laying down lines and shapes that will serve as walls and/or obstacles that will block out light or line of sight.

DL Layer.jpg


How to Activate Dynamic Lighting

Open up your Page Settings and check the checkbox to activate Dynamic Lighting for that page. The first option Enables the dynamic lighting and the other options add functionality to the dynamic lighting system. You can use Fog of War in combination with Dynamic Lighting, but one is not dependent on the other to function.

If you or your players suffer from sluggish dynamic lighting render results you might want to consider checking the option Only Update on Drop. What this option does when checked is that the tabletop only redraws the dynamic lighting after a token has been picked up and placed elsewhere on the map. This can lessen the render burden for users running on old computers or when a GM is working with a very large or complex map.


Troubleshooting

If all players can see everything while Dynamic Lighting is enabled, ensure that Global Illumination is not checked on that particular Page.

If one particular player can see everything, try having them toggle their browser's Hardware Acceleration on or off.

If one particular player cannot see anything while Dynamic Lighting is enabled, ensure the following:

  • Has Sight is checked on their Token's Advanced Tab.
  • They have permission to control their Token. (If their Token represents a character, ensure that they have permission to control that character.)
  • All Players See Light is checked on the light source Token's Advanced Tab.
  • Fog of War is not blocking their Token's vision.

How to Add Light Obstructions

While on the Dynamic Lighting Layer, you can use all of the drawing tools available to create lines and shapes to draw walls, columns, doors, etc (except the freehand tool). You can also utilize color to help differentiate different types of light obstructions (ex. lime green for stationary dungeon walls and bright red for doors).

Use the drawing tools to draw outlines of all the walls and other pieces of the map that you want to block light. We suggest using the Polygon Tool for best results. Due to the performance hit associated with using it, the Freehand Tool is disabled while you are on the Dynamic Lighting layer.

Remember that any drawings or tokens added to the dynamic lighting layer are invisible whenever the dynamic lighting layer is not selected. You can use this fact to put overhead or other 'invisible' lighting sources on a map by placing light emitting tokens onto the Dynamic Lighting layer.

Note: Presently, circles drawn with the Circle Tool do not render light blocking correctly. Instead of using circles, create a rounded shape with the Polygon Tool.

If you plan to block out a multi-room/complex map, it's recommended that you build the light blocking with smaller individual lines. This makes it easier to select and move around the shapes you add to the layer.


Adding Light

Tokensettinglighting.png

Now that you have your obstacles drawn out on the Dynamic Lighting Layer, you have to add light to your Page. Light is emitted via tokens. Create a token and place it on the map.

Double click on the token and select the Advanced tab. There you will find the option Emits Light. This option allows you to enter a light radius amount and gives you a checkbox for All Players See Light. When the checkbox is left unchecked, the only player(s) who can see that token’s light emission are those who have assigned permission to that token.

By default, the light will start to "dim" about 5 feet (or units) before the selected maximum radius. This effect can be modified by using the optional "Start of Dim" value in the "Advanced" tab. To make the dimmed area larger, set the "start of dim" value to be much smaller than the radius (e.g., 20/5). To make the edge of the light a "hard" transition, make the "start of dim" value larger than the light radius value (e.g., 20/30).

It is possible to create dim light with no bright source. This is useful for creating effect where the light is coming from under a door or through curtains or shutters. Simply set the "Start of Dim" value to -5

Hold down the alt key while moving the token to prevent it from snapping to the grid.


Line of Sight

Line of Sight restricts players to only see lights that are within the appropriate field of vision for the tokens that they control. This means that a light on the other side of a wall won’t be visible to a player until they’re in that room, even if it’s a light that’s visible to all players. The image below shows the difference between a dungeon without line of sight, and then with line of sight enabled:

Lineofsight.gif

To enable line of sight you will need the "Line of Sight" Checkbox on the Page Settings checked, as well as having one or more tokens that the player controls have "Has Sight" checked otherwise your players won't see anything but darkness.

GMs can also highlight a token and press Ctrl+L to view the scene restricted to the line of sight of the selected token. In addition to the line of sight feature, you can now customize the “angle” of lights and the line of sight of tokens. So you can specify, for example, that a player should only have a 140-degree field of view instead of the default 360-degrees. To do so, use the "Angle" setting on the Token Settings screen to change the angle of the light emitted or the angle of the line of sight for the token.

The token's vision can be further customized using the multiplier feature. The multiplier affects how far the token can see from existing light sources. This is a good way to simulate a character who has the ability to see further than normal in low light situations or has an alternate form of vision that might allow them to navigate in the dark. For example, someone who can see twice as far in low light would have a multiplier of two.


Restrict Movement

Restrictplayermovement.gif

The "Restrict Movement" checkbox enforces that player controlled tokens, that also have the "Has Sight" box checked, cannot cross over Dynamic Lighting Obstructions. This ensures that players don't move outside the intended map area and accidentally reveal parts of the map their tokens couldn't otherwise see. It can also be used without Dynamic Lighting checked as a way of restricting parts of the map from player token movement.


Global Illumination

With "Global Illumination" checked along with "Enforce Line of Sight" the map is blanketed in light, with the only restriction to vision being Dynamic Lighting Obstructions. This options simulates daytime, outdoor, or brightly lit environments where the only limits to range of vision are physical obstacles.


Advice for Best Performance

The Fewer Lines, the Better the Performance

Every single segment drawn on the Dynamic Lighting layer is taken in account each time Roll20 updates the ray-tracing process that determines what is revealed and what isn't. This happens every screen refresh as you move tokens projecting light/sight around the Tabletop. If you have "Update on Drop" enabled, the ray-tracing is performed only after you pick up a token and place it elsewhere on the page. Complex outlining drawn on the dynamic lighting layer, can cause the Dynamic Lighting feature to become very resource intensive and potentially cause lag during gameplay for you or your players. You can keep a page running smoother if you focus on efficient contouring while drawing your Dynamic Lighting outline and avoid tracing over previously drawn lines. If your dynamic lighting is performing sluggishly, your outline complexity should be the first thing to review.

An example where efficient outlining should be used is when drawing in the walls for organic-shaped areas such as cavern passages. Attempting to perfectly trace the contours of the natural rock face wall would require many segments, so we recommend outlining only the most basic direction of the cavern wall.

Don't Use Circles

A circle drawn on the Tabletop isn't represented by a series of segments, instead, it is a vector calculation that draws a spline between four vertices. Since there aren't any true segments used for a circle shape, there is nothing there for the Dynamic Lighting system to reliably ray-trace as you would expect regular linework on the Dynamic Lighting layer should. If you need a circular shape for your Dynamic Lighting, we recommend drawing it out as a rounded polygon instead.

Don't Rotate Shapes/Drawings

Currently, the Dynamic Lighting ray-tracing only takes in to account the original location of the vertices of a shape or line segments in relation to each other. You can copy and paste shapes and lines, move them, and scale them freely; however, you can not rotate them. If you rotate a shape or line, the dynamic lighting will remain the same as it was before you rotated the object.

Opting for Global Illumination

Depending on the battle map you're illuminating with torch and candle tokens, you may choose to enable Global Illumination instead. The more light sources you put on a Page, the required calculation for Dynamic Lighting raytracing increases. If you enable Line of Sight and Global Illumination together, you won't need to place light sources for players to view the room/area their tokens are currently within. Other portions of the Page hidden away by dynamic lighting walls will still be hidden until the players move their tokens to that area. You may also choose to click Global Illumination on and off depending on where the players are at and what the lighting environment is like. For instance, if there's an underground dungeon where some areas are lit up and others not, you can turn on Global Illumination only for the periods your players' tokens are currently residing within regions intended to be well lit. When the party journeys through the unlit parts of the dungeon, the GM can disable Global Illumination on the page to require light sources to guide the players' way.

Being Mindful of "Has Sight"

As the GM, if every token on a Page has "Has Sight" enabled, this can cause some processing lag because the Dynamic Lighting is ray-tracing for every single token that has this option enabled. This is unlikely to be an issue players' browser clients, as they'll only ever see sight enabled on the tokens they directly control. As the GM may want to disable "Has Sight" from NPC tokens for efficiency sake or only enable "Has Sight" for one token in group of monsters to serve as the group's range of sight.

Avoid Using Thin Line Weight

Vertical lines drawn with the polygon tool, can be very difficult to select when their line weight is set to Thin (the narrowest line weight setting). If you ever find yourself in a situation where you can't select Thin weighted lines, hit the keyboard shortcut CTRL+A to select all elements on the Dynamic Lighting Layer. While selected, you can assign a line weight to all content at once by choosing the one you prefer when you have the Drawing Tools submenu selected from the Tabletop Toolbar. Changing the line weight to any other setting thicker than Thin will allow you to individually select pieces of linework again.


Common Tips and Tricks

+s and Xs for Trees, Columns, Stalagmites, and Other Vision Obstructions

Draw an X or +, instead of drawing an enclosing polygon or rectangle to obscure small vision obstructions like trees and columns. This will give you the desired effect of blocking line of sight, but also leaving enough of the map art visible for the Player to have an easier time recognizing what is obscuring their view. The added bonus of this technique is that a + or an X is very ray-trace efficient if you're working on a very complicated dungeon on the Dynamic Lighting Layer.

Light Source Tokens on the Dynamic Lighting Layer

You can place tokens of candles, campfires, torches on a battle map and give them light settings to emulate lit areas on a map. If your battle map already has illustrations of lit props built into the art where adding additional light source tokens would detract from the overall look, you can instead place light-casting tokens on the Dynamic Lighting layer directly. Tokens placed on this layer will not be visible to the PCs, but the light they cast will be visible. Because the token isn't visible, you don't actually have to be concerned about the art being used for the light source tokens. You can use whatever art is most convenient for you. Tokens on the Dynamic Lighting layer behave like art placed on the Background Layer—they will not have the token UI elements like the bars and Settings Gear icon. You can still access the Token Settings dialog window while on the Dynamic Lighting layer (and the Background Layer too) by double-clicking on the token.

Choosing Alternate Colors for Walls and Doors

The color you choose for the linework of your Dynamic Lighting doesn't have any effect on its behavior. Using different colors for doors and walls makes it easier for the GM to locate the linework placed over doorways that they will eventually have to move out of the way for the Players' tokens.

Portcullises, Prison Bars, Fences, and Palisades

If you have walls that would only partially obscure vision like portcullises, prison bars, tightly-built fences, or loosely-constructed palisades, you may find creating a dotted line or a series of rectangles drawn over the area can create an aesthetically pleasing effect when your players look through to the other side of the "wall". A word of caution about this approach - too many lines drawn in this fashion can make ray-tracing for the Dynamic Lighting lag. It also might make it difficult to select all of the lines/shapes that make up a partial wall if you're too meticulous to block out every single metal bar or wooden stake. You don't have to follow the art's depiction of the individual bars precisely to give your players the impression of looking through a castle portcullis.
 

Simulating Elevation Line-of-Sight

At present, there isn't a means to have Dynamic Lighting block line-of-sight in only one direction. There are tactics to make elevation changes blocking line of sight by creating walls that are not attached to the rest of the room that hug the edge of an elevation change (like a cliff edge). When the players are viewing the room from the higher elevation, move these walls out of the current room so they no longer are blocking line of sight. Move the elevation walls back into place if the players are later on the lower level and can no longer view the upper elevation level (or vise versa if the players start low and eventually reach the higher elevation later on). You may want to change the color of this linework so it easier to tell what parts of the room are meant to be moved out of view as your players traverse through it.

Adding a Lip to Your Wall Outlines

While drawing the outline of walls and doors, draw them pulled back a little bit from the very edge of the artwork. This way, while the Player is navigating the environment, they can see the edges of the walls, instead of a floor that ends off into complete darkness. This will make it easier for the players to discern when they reach a window or a door or some other detail on the artwork that they should be able to see.

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