Thursday, May 25, 2017

Usable Maps

Recently there was a blog post on the Monsters and Manuals blog about what makes a map useful or not and Cecil posted his own thoughts on it on his own Sword Peddler blog.  This prompted me to gather some of my thoughts about what makes a map usable (in contrast to useful as applied in the blog posts) in Virtual Tabletop programs.
Of course much of what follows are my opinions and personal preferences but they are based on more than a decade of using VTT programs and MapTool in particular.  Some of my comments are about the technical choices to be made when producing maps and some deal more with aesthetic choices.  My goal here is to provide some insight from a VTT user perspective for those map creators who may or may not actually use VTT programs.  First some definitions so that we are all on the same page.

Definition of Terms

Virtual Tabletop (VTT) - Programs used to display maps and other graphic content for players and GMs.  Replaces the vinyl battlemats and wet erase markers.
Pixels per Grid (PPG) - A measure of map resolution and scale.  PPG defines how many image pixels are used for each grid cell whether square or hex.  This is not given in DPI as monitor and laptop displays are not all the same in how many pixels they have per inch of display.  PPG defines the scale of the map independent of the display it is to be viewed on.
Tactical Map - Maps for encounters and combat.  They may represent an entire dungeon level, a building floor or an outdoor encounter area.  When a grid is present this typically represents 5 feet, though 1 yard/meter, and 2 yards/meters are not uncommon.  Separate images known as tokens take the place of miniatures used on the game table.

Maps For Virtual Tabletop Use

What is Usable?

Pretty much any map can be made to work in a VTT depending upon the GM's wants and needs but if the map is being created with use in a VTT in mind then there are design choices that can make them more usable.  Choices that can reduce the effort a GM has to put into game session prep.   For me usable means that I have to do little or no fixing of the map before using it in my VTT program.  That I can load it directly in the VTT with little or no tweaking to match a grid.  That I don't have to spend time in GIMP editing out details only the GM should know.  There are a number of different factors that play into this and I’ve commented on some of them below.

Map Resolution

It is important to supply enough resolution in the map image so as to clearly present the map to the GM and players.  I refer to this resolution as the Pixels per Grid or PPG of the map.  There is no standard for PPG among the various VTTs and some can use any grid size while others have a fixed size.  For VTT use, a minimum of 50 PPG for tactical maps is recommended.  This value provides an adequate balance of resolution and file size.  A maximum PPG of 100 gives 4 times the detail and allows the GM to scale a map down to a smaller PPG size if needed/desired but is not so large as to overtax most PCs.  Going larger is rarely justified and generally doesn’t provide much value to the player who is likely looking at his map zoomed out so as to see more of it.  In my experience with VTTs, most player and GM displays are typically zoomed out such that there are 30-50 screen pixels per displayed grid cell.  This is so they can see more of the tactical display.  A typical HD display of 1920x1080 gives you a 38x21 grid cell view of the map at 50 PPG but only a quarter of that, 19x10, at 100 PPG.  That doesn’t take into account the part of the display used for character information or a dice roller and such.  Maps with a higher resolution aren’t adding any additional value in these situations but are still using more memory, creating more load on the user’s PC and using more bandwidth when sent out over the net to the player’s clients.  When VTT users zoom in, it is mostly to get a better view of a monster/character token or some piece of set dressing.  As these are separate images with their own resolution that can, and should, be independent of the map resolution, a higher map resolution isn’t of benefit.
Beyond the question of whether or not there is a benefit from higher resolution maps for the players there is also the practical matter of computer and network resources.  A 100 PPG map uses 4x as much memory as a 50 PPG map that represents the same area.  The file size for the 100 PPG map will be corresponding larger, taking longer to transfer over the net to each of the player clients.  For example, a moderate-sized outdoor encounter map that represents an area 100 yards on a side would be 60x60 grid cells at 5’/grid.  The 50 PPG version is 9000 pixels on a side and uses 34.33 MBytes of memory.  File size in JPEG format will be ~1.75 depending on content and quality level chosen.  The 100 PPG version will weigh in at 137.33 MBytes in memory and 6 to 7 MB on disk.  For most modern PCs with high-speed internet connections this isn’t as much of a concern but the guy with the middle-of-the-road laptop with a basic connection will certainly appreciate it.
Maps created with 50 to 100 PPG in general work well in VTT programs.  A PPG of 60 is nice for 5 foot grids as each pixel is then 1 inch.  Using 72 PPG does the same for 6 foot grids.  100 PPG works out nicely for those with 1 meter grids.

Map Grids

In general I prefer no grid on the maps I purchase or acquire as long as it is clear what the PPG of the map is meant to be.  Most, if not all, VTT programs can overlay a grid on the map and it is this grid that the VTT program uses internally when tracking movement distance for tokens.  Having a nice map with a wonky grid that just doesn’t quite line up with that of the VTT is distracting and irritating for GM and players.  Another benefit of a map with no grid is that the GM can use whatever grid size and style he wants.  Say the map was created at 100 PPG and with each grid representing 5 feet.  If the GM is running a game system that does movement in yards he can easily set the VTT grid size to 60 PPG and now token movement in the VTT is to the correct scale.
If feel you must put a grid on a map, first, get it right.  If the map is 50 PPG and 60 grid squares wide then the map should be 3000 pixels wide.  Not 2996 and not 3008.  Use a filter or plugin that can layout grids precisely and define them in pixels and not inches.  Second, put the grid on the map at the target resolution.  If you are constructing the map at 300 PPG so that you can have a nice version for printing and a smaller 100 PPG version for VTT use, don’t put the grid on the 300 PPG version and then scale the image down to 100 PPG.  Scale first to 100 PPG then add the grid.  Third, the grid shouldn’t be a distraction from the map.  It should be visible when looked for but not in your face.  Keep it thin.  Maybe 6-8% of the PPG value.  The map is the important part; the grid is bookkeeping.  If the map is built-up digitally in layers, consider putting the grid only over the base floor/ground imagery and not over the top of walls or room contents.  For dungeon/building maps with a square grid it can be part of the floor texture.  The grid is obvious but doesn’t distract from the map.  The image below (from one of Kristian Richard’s awesome dungeon tiles) shows how the floor texture can also be the grid.

Grid as part of floor texture.

Map Detail

More detail isn’t automatically better than minimal detail.  The adage less is more can certainly apply to maps for gaming and use in VTT programs.  There should be enough detail to set the stage but not so much as to distract from what’s happening.  Too much can have the players focused on stuff that isn’t important or even part of the ongoing story.  To be fair, sometimes extra detail in a map can inspire a GM with other ideas or alternative paths for adventures.  When you are searching for ideas on a new adventure, browsing through your collection of highly detailed maps can spark that idea that leads to a new adventure.
Overly detailed maps can also take away GM options.  If a room is loaded with tables, barrels and cabinets on the map image, the GM has to be ready to explain what is inside of or on top of them.  Or a GM will just say, “you find nothing of interest”, or worse, “ignore that stuff, it isn’t really there”, as the players go through such a room.  How often does this happen?  I believe it happens all too often and this takes the players out of the moment.  If the map creator is making maps to sell then the time spent putting in detail that isn’t needed or used means that time was wasted and it may just cause the GM to look for other map sources in the future.  An obvious exception to this is when the map is provided as part of a full adventure module and the contents of the room do have significance within the context of the adventure.  Another exception is if the map is specifically themed such as a “Temple of an Evil God” map.  Decorative touches that reinforce the theme will generally be welcome.
Map creators should keep in mind that most VTT programs allow multiple layers of imagery to be displayed.  The set dressing objects can be supplied as separate images to be placed on the map where and as the GM needs.  Doing this also gives a lot of extra value to the GM as these objects can be used again on other maps to carry that theme forward.  As the digital artist is almost certainly creating these objects as individual images first before adding them to the map there is little additional work involved.

Map Objects & Tokens

As suggested above, tokens and map objects can be supplied as separate image files at a higher resolution than the map they are intended to be used with.  Generally speaking a PPG of 200 to 300 is good for tokens or objects that fill 80% or so of a 5 foot grid cell.  Tokens representing smaller creatures or objects that are less than a couple feet across can benefit from more resolution.  This is a nice bonus for the GM as they can be used at that resolution in the VTT using the built-in resizing (not scaled down outside of the VTT) functionality so that when a player zooms in all of the glorious detail is there to be seen.  Here is an example:

Higher resolution tokens on a 50 PPG map.

The top half shows a simple encounter map created in MapTool and that image was captured at 1:1 zoom.  The PPG for the map is 50.  The keen-eyed player might see something on top of the barrel the crossbow-wielding foe is hiding behind.  Zooming in, a lot, the player sees it is a parchment with a message.  The parchment image was created at 250 PPG and is close to 1:1 at this zoom level.  The archer token (by Devin Night) is about the same resolution.  They still look good at this extreme zoom level even though map textures are pixelated and the lower resolution barrel is suffering somewhat.

Map Style: Photo-Realistic vs. Hand Drawn

There are many different ways to create maps with a variety of tools both digital and traditional.  All can produce maps suitable for use with a VTT.  Maps for gaming can be generally divided into two types or styles: Photo-Realistic and Hand Drawn.
Photo-realistic maps are constructed from real-world imagery using photos of vegetation, soil, rocks, cliff faces, debris and other naturally occurring items plus man-made like cobble-stone streets, rock walls, lumber, metal, floor tiles and rugs.  These images are then manipulated, merged and blended together with tools like Photoshop to produce life-like imagery on maps.  Maps like these can be beautiful and enhance the viewer’s immersion into the setting the map represents but there can be problems when used in VTTs.
Busy floor/ground textures or cluttered map backgrounds can make it hard to see top-down tokens or other details and, when zoomed in on, often become a pixelated mess.  Real-world items have complex edges, textures and colors.  A digital photo of a parquet table looks good at the full resolution but when scaled down to only 50 or 100 pixels all of the subtle detail just blurs away.  Using the 200 to 300 PPG scale I suggested above for tokens and map objects as individual images can help.  Photo-realistic maps often get considerably less attractive at zoom levels less than 50% or above 200%.
Hand drawn maps are, as the name implies, hand drawn either with conventional tools and media or digitally with a stylus and tablet but also includes maps created using the line, path or polygon tools in paint programs.  They vary from simple black and white up to fully colored and textured.  Hand drawn maps can be every bit as attractive as the photo-realistic map and can approach realistic levels of detail.  One of their strengths is that they can have a more authentic feel for fantasy games in that they can look much like something that was scrawled on a piece of parchment.  They also tend to not be overly-detailed, having only the detail and information that is needed.

Map Content

There are some things that don’t need to be and shouldn’t be included on maps meant for VTT use.  Remember that VTT maps are player-facing maps and not GM maps.  The first of the items not to include is doors.  Don’t put them in.  VTT programs easily handle adding doors to maps and can depict them open or closed.  This is another item best supplied as a separate image at a higher resolution.  Next is secret door and trap markers. Again, VTT maps are player-facing.  GM information, if truly needed, can be provided on a separate GM version of the map that has that information clearly marked.  As with regular doors, secret doors and traps are easily dealt with using the features of the VTT program.  Most have a GM layer that these objects or markers can be placed on so that they aren’t visible to the players.  If you made some really spiffy door or marker graphics, bundle them up with the map as separate files.  The GM will be grateful to have items that fit in with the style of the map.  Falling into this same category is room numbers or labels.  These belong on a GM layer and the information can be provided to the GM on a separate map.
Another class of items best left out is light sources like torches, candles and lanterns.  Once again, putting them in has automatically limited the GMs options or forced them to tell the players, “Ignore the torches on the walls.  They aren’t really there.”  Light sources can also be supplied as separate images and placed as desired by the GM.  Most commonly seen with the photo-realistic style of maps, some map creators will supply lit and unlit versions of map.  These maps often look fantastic and certainly provide more mood and atmosphere.  They just more narrowly constrain the potential uses of the map.

Map Shadows

Shadows add depth and can make it easier to perceive height differences between map features and they create separation between the floor and objects sitting on the floor.  They also can be overdone and detract from the overall map.  Like grids they shouldn’t be the first thing someone notices about the map.
Shadows can be directional or non-directional.  I prefer non-directional shadows for a couple of reasons.  First is that a directional shadow means there is a light source shining from the direction opposite that of the shadow.  What light is going to be shining in from outside and through the ceiling of a room in a dungeon so as to create shadows at the base of just the north and west walls?  None of course.  With outdoors maps the light source could be the sun or moon but now the map is tied to a specific time of day.  The next reason applies more to objects used on maps or map tiles.  Map objects and tiles with non-directional shadows can be rotated or flipped without causing there to be a mismatch with other shadows on the map.  Finally directional shadows take more work to get right.  A directional shadow for a chair or table needs to depict the legs in the shadow.  The shadow of a statue will be the profile and so on.

Map Sizes

There is no reason for maps intended for use in a VTT to be sized to standard paper sizes.  The V in VTT stands for virtual and the map space is virtually unlimited or at least not constrained to 8-½ by 11.  There are, of course, memory and bandwidth considerations to take into account as I mentioned above but, in general, a map should be as large as it needs to be.  It’s frustrating as a GM to get a lovely map of a building but the image has been cropped to within 5’ or 10’ of the building.  Chances are the map image shows a grass, dirt or stone texture around the building but the VTT GM will just have to match it as best he can if he needs to show the surrounding area.  If the map creator supplies the background texture as a seamless image tile the VTT GM can use that for the background and then place the map on top of it creating as much battle space as needed.
One final point about map sizes, they should be created in whole multiples of the grid size.  If the map is created for use at 100 PPG, the image dimensions should be integer multiples of 100.  If the map is 10 grid squares wide and high the map image should be 1000x1000 pixels.

Map Image Format

For the majority of maps JPEG should be used for your output files.  Save the map at a reasonably high quality level (~90% in GIMP) and you won’t have obvious artifacts but you will have reasonable file sizes.  Two-color or low-color maps can sometimes be saved in PNG format and have small file sizes.  Test it and see.  For archival purposes keep a copy in PNG as well as the native save format of whatever program you are using.
Tokens or map objects should be saved in PNG format.  Most will need alpha-channel support for transparent areas and this is the format that is going to give it to you in a nice lossless but reasonably compressed file.

That pretty much covers the issues that impact me the most.  Would be interested in hearing from others what their experiences with adapting maps for use in VTTs has been.

[Edit 1] Samuel Penn on G+ pointed out something that I had originally planned on including but later left out which is that when the map artists draws the dungeon or building walls if the walls straddle the grid lines it makes it much easier on the VTT GM when it comes time to add the Fog of War/Vision Blocking Layer in the VTT.  This helps ensure that a portion of the wall will always be visible from the player view.  Examples can be seen in the comments on G+.  Thanks Samuel for reminding me of this.


  1. Incredible! Almost spot on for what I was looking for, and written to be clear and easily understood. Thank you.

  2. Thanks, too.
    As far as I remember, MapTools allows resizing the map. How do other virtual tabletops?

    1. MapTool does allow you to resize any images you drop on a map including background images which could include the map itself. I'm pretty sure that Roll20 also allows this but it has been a year or more since I looked at it. I'm not sure about Battlegrounds or Fantasy Grounds.