After I finished GMing a session set at night, a couple players noted that it would have been nice to know where the town torches were lit so that they could take advantage of the dark alleyways to sneak around. So, I got to work on a lighting system and finished it within two weeks.

Some virtual tabletops use a paint and erase method of setting the lighting areas. I opted for the plot and adjust method, since for now it allows the best options for placing the lighting volumes exactly as you want them and allows for fine adjustments.

Setting up lighting in TTopRPG can be a complex process, and it most certainly isn't required. But if you are willing to do so, it can make the environments much more immersive and help you adjudicate the effects of lighting in your game.

This article will discuss lighting techniques to help make the best use of the system (at least the way it looks best for me).

Light sources

Light sources are objects you place to generate light on the map. You can attach them to icons so that they move automatically with the icons as they are moved. You can also turn them on or off with a hit of the V key (note that an invisible icon can still have a visible light source attached to it).

How the light appears depends on the type of light and the Ambience setting.

* When Lighting is (off), the map applies no lighting at all. Everything is bright.
* When Ambience is set to Full, lights in fully lit areas contribute nothing, but they will illuminate areas that are darkened with special wall volumes (see the end of this article).
* When Ambience is Shadowy, full light sources will generate a circle that represents their full illumination area. Shadowy light sources contribute nothing.
* When Ambience is Darkness, full light sources will generate a full light area and a shadowy area farther out.

A full and shadowy light source in Ambience Darkness


Plotting a wall

In the Lighting menu, select Add Wall to begin a plot. Left click to place a point. As long as you hold the button down, you can adjust the point's position until you lift up. To end the plot, either place the final point on the wall's starting point, or right click once.

Wall normals (facing)

Before we begin, you need to understand what a wall normal is. When you plot a wall, you will see an arrow telling you which direction you have been plotting the wall, but there will also be a small line segment poking out from the midpoint of each line. This is the wall normal and is used to help calculate which side of the wall light should cast a shadow from.

A wall will cast a shadow from a light source when its normal faces the light source.

Usually, I face the shadow wall normals into the solid surfaces I am plotting around. For darkness walls, I face them outward into the room. This allows light to illuminate the walls that are plotted as shadow but casts a shadow off the backside. It also keeps the inner surfaces of walls plotted with darkness hidden.

I handle doors and secret doors a little differently, which I'll cover after lighting wall surfaces.

When you are plotting walls, if the normals are facing the wrong way, don't worry - after you are done plotting, just right click on the wall and Flip the facing (or highlight the wall and hit F).

Shadow walls vs. darkness walls

Shadow walls will take full illumination and cast a shadowy area from it. They also take shadowy illumination and cast darkness from it.

This kind of wall is good for thin columns in a room that cast a shadow but do not totally block light. I also usually place shadow walls around every wall surface on the map that can possibly cast a shadow.

Darkness walls take all kinds of illumination and reduce them to darkness. This kind of wall is useful for preventing light sources from illuminating rooms through walls that shouldn't allow any light through at all.

Darkness walls are used in combination with shadow walls on the same surfaces to produce a shadowy halo effect around corners and doorways.

Not every surface will have both shadow and darkness walls. Pillars in a large room, for example, may cast a shadow but shouldn't be enough to block light entirely on the other side, so they only need shadow walls. Large wall sections, however, should block light with their mid-sections, so they will require both.

Light sources interacting with shadow and darkness walls in Ambience darkness


Preparing lighting on a map - shadow walls

When I set up a map for lighting, I usually start with all of the shadow walls. I plot around every wall and column that will ever possibly cast a shadow, placing it directly on the edges.

I don't plot across normal doorways - instead I treat the map as if doors are not there for now, applying the shadow wall instead to the smaller walls making up the doorway and skipping the door itself.

Secret doors are handled a little differently. As with normal doorways, I don't plot a shadow on the door itself. But I also don't plot the wall along the inside doorway either. Instead, I stop the plot where the secret door begins and start a new one on the other side. This prevents lighting inside the room from revealing the presence of the secret door by casting a shadow. Note that this only works if the shadow wall's normals face into the solid wall.

Shadow walls should follow the very edge of the walls. Notice the breaks in the walls at the secret door to the right.


Preparing lighting on a map - darkness walls

New walls are always plotted as shadow walls. After you are done plotting, set the plotted wall as a darkness wall by either hitting L with the wall highlighted or right click and Set Full Light to Darkness.

After the shadow walls are placed, I start plotting the darkness walls. For normal walls, I usually place the darkness walls just a little bit inset, about 1-2 feet or so inside the wall. For thin walls that you plan to use to block all light, you must place the wall in both directions - start at one end, trace along the inside in one direction, then come back to complete the loop. To understand this, imagine what you would do to trace along the outer edge of the wall. You would naturally loop around the entire wall section and eventually arrive back where you started. So when you place the darkness wall inside the section, you'll follow nearly the same path, just inside a little.

Again, avoid doorways and the space across secret doors. But you don't have to do anything fancy for secret doors this time, just plot the darkness wall as if the secret door is opened.

Darkness walls are slightly inset with normals pointing outward instead of inward


Doors and secret doors

Finally, to complete the wall plots, you need to set up darkness walls on the doorways.

The goal for normal doors is to allow light to illuminate them from each side but not allow light to get through. What I usually do is plot a small darkness wall facing inward instead of outward around the door, intersecting the nearby darkness walls I plotted earlier. After the wall is placed, right click the wall and Show its Indicator. This creates a small square indicator that you can use during play with the V key to deactivate the wall as the door is opened.



For secret doors, it's important for them to appear as normal walls until they are opened. So plot the darkness wall facing outward as you would a normal wall, intersecting it with the darkness walls you plotted before. Show its Indicator so you can deactivate the wall at a later time.



The completed results:

Door Walls Activated


Door Walls Deactivated


Here is the same map with a few more columns and wall sections added, and the light's radius reduced a little


Maximum points per wall

Sometimes, when you are plotting a complex wall, you'll hit the maximum of 200 points before you are finished.

Just right click to finish the plot and start a new one. You can adjust each wall individually later.

Adjustments

Inevitably you will need to make adjustments. You can't adjust points you have already laid while you are actually plotting the wall, but afterwards you can grab points and drag them around, delete points or the entire wall, insert a new point just after a highlighted point, continue a plot from the wall's endpoint, and split the wall into two sections. You cannot rejoin two walls after you separate them.

All of these options are available from the right click menu, and as hot keys shown in the menu itself.

Darkness volumes

Eventually I needed darker areas on a map that was normally fully lit (such as a cave complex on the same map as a town in full daylight).

To accomplish this, simply plot a large shadow wall to contain the area you want to darken, then right click the wall and set its mode at the bottom of the right click menu.

The Diminished Ambience option sets the volume type depending on the Ambient light setting. Diminished Ambience will generate a shadowy volume when Ambience is set to Full, and darkness when Ambience is Shadowy. When Ambience is set to Darkness, the volumes are ignored because they don't contribute anything.

Note also that if you have Lighting set to OFF, you will not see these areas darken the map.

Also, these darker volumes look better if, at the sides where outside light would illuminate them, they are surrounded at their edges by the darkness walls, not the other way around. The closer they are to each other, the better, since if the Ambience is set to Shadowy, then there will be a small band of shadow visible around the darkness volume when a full light source is nearby.

Note at the right how the darkness wall contains the darkness volume from the outside light


Illuminated areas

In contrast, if you want darker areas of a map to be fully illuminated, you accomplish this with the use of placed light sources.

Note that the light type has options of Ambience and Diminished Ambience. These are used to place light sources that illuminate darkness volumes. For instance, in the town with a cave example with Ambience set to Full, an Ambience light source at the mouth of the cave will allow the outside sunlight to illuminate the entrance to the cave, making the scene seem more natural. A Diminished Ambience light source, then, would generate only shadowy illumination.

A final caution

As nice as lighting can look on a map, placing many light sources along with many shadow and darkness walls can HORRIBLY slow down the rendering, making map scrolling and mouse-overs less responsive. So be careful how many active light sources are in place at one time.

If you need to know how much lighting is affecting everyone's render speed, type /fps in the chat area. 10+ fps is playable. If it's less than that, consider disabling some light sources.

Hopefully these explanations allow you to make fuller use of the lighting system.