Can someone who knows about VTT explain how to convert paper maps?

[Johs]

My company has recently started creating Battle Maps for use with other roleplaying games (and in time, our own as well).

I've been asked by some of our fans if there's a way they can use these maps for their online VTT games... which sounds nice in theory, but I have no idea what that would require.

Is there i way I can simply remap a finished file and upload it somewhere? Do they need the file in a certain digital format?

[Midgardsormr]

VTTs typically use a common image file format like jpg or png. Usually the former since the files often compress better. For my games, I usually use a resolution of 100 pixels per square. That seems to get me the best results for speed of file transfer versus visual quality. Since everyone at the table has to download the map and all of the tokens, it becomes important to manage those file sizes. Some people may like larger resolutions, though. You might ask the fans what size they'd like to see.

GMs using a VTT frequently like to have many items on the map as individual tokens. These are usually saved in PNG format so they can have transparent pixels (allowing images that do not appear to be rectangular). Doors should almost certainly be tokens of this kind, as should anything the PCs or NPCs are likely to move, smash, or throw at one another.

Helpful hint for doors: Make the door image twice as wide as it needs to be, with the hinge in the center of the token. That way, a simple rotation can open or close it, without the GM having to reposition it.

You will probably want to make gridded and gridless versions available. Most VTTs can generate their own grids, and it's usually easier to line things up if you're not trying to align it precisely with a burned-in grid.

If you want to get really detailed, you could make some packages of prepared VTT scenario files with the maps already set up. I find that one of the most time-consuming parts of prepping a MapTool session is getting the visibility layer set up. This is an extra layer of information that tells the VTT where objects that block line-of-sight are. With that set up, the software will automatically handle fog-of-war and lighting effects based on the locations of the players' tokens. Very useful, but a bit of a pain to configure.

[Neyjour]

Like Midgardsormr said, JPG is usually the most common format.

I think some VTTs use grid squares of 50x50, but 100x100 is more common I believe (1 square = 100x100 pixels = 5 feet), so probably best to go with that IMO (that's how I make mine, and I've had no complaints), and if they need a smaller size, they can just resize it down themselves.

Once you've figured out the scale of your map and resized it, you're done for the gridless version. But I definitely agree with Midgardsormr, that including a gridded version is also a good idea. To do that, you'll need a grid with a transparent background. (If you need help with that, I can make one for you, at whatever dimensions you want). Then you just add the grid as a new layer on top of your map, merge the two and again, save in .JPG format. You can also play with brightness/contrast, colours, drop shadows, layer modes and transparency, etc. to get different effects for the grid, and make it more esthetically pleasing and such. For example, just dropping a solid black grid on top of your map probably wouldn't look very good. And I've seen other people use solid colours like bright yellow, which looks...very ugly, and distracts from the actual art of the map.

Can you link us to one of the maps you'd like to convert for VTT? Having a visual might help with giving you more specific information on what you can (or need) to do.

[Johs]

Here are a few visuals:

WineCellar-G-Layout2.jpg Dungeon-Layout-5.jpg

[mthomas768]

Here are a few visuals:

As a test I grabbed the wine cellar you included here, and dropped it straight into Roll20 without any issue. The application allows you to designate the vertical / horizontal grid-count, so set that and the page size correctly, and it aligned with no issues.

[Neyjour]

Okay, hmmm... with the size not being divisible by 100, I'm not really sure how to make it work properly.

The only thing I can think of is to "stretch and squish" them (resizing by unlocking the aspect ratio). So for example, the winecellar would be resized to 1600x1200 instead of the current 1584x1224. The differences are small enough that you really can't see the distortion. I doubt anyone would even notice...

I'm attaching an example for you to compare, with a 100x100 grid dropped on top.

Do you have larger resolutions of these? If you do, start with the largest resolution you've got and try this method of resizing to get a number divisible by 100. And go either up or down depending on which direction is the least amount. Like for the width of the winecellar, I resized up by 16 pixels rather than down by 84. And for the height, I resized down by 24 instead of up by 76. Once you've got that done, then just start experimenting with resizing the map down (always keeping it divisible by 100) until the scale looks right (1 square = 100x100 pix = 5 feet).

EDIT: And you'll want to do this with the clean version, that doesn't have your original grid on it. So once you've got the correct dimensions, you'll save it as your ungridded map, and then lay your new 100x100 grid on top for the grid version. I like to do my grids like you've done here, with the grid on the floor (under all the objects and such) instead of on top of everything. It would be kind of tedious and time-consuming, but you could use a soft eraser brush to erase the grid lines where they fall on top of the objects, walls, etc. Then when you're done, merge the two layers and save as a .JPG.

[Johs]

This all sounds really easy, it wont be a problem at all to resize and regrid at 100x100 pixel grids. However, I'm still a little unsure about "what" the VTT format is? It's just basically an image that has a consistant size so that the image can be imported and mapped for VTT use? It sounds like my backers might be happy with just access to the high quality .JPGs.

I wouldn't mind going through the extra steps on their behalf to make them a clean version that's ideal for VTT, but the only thing VTT "needs" is an image?

[Neyjour]

Yep, all you need is a .JPG image for the map. There's no actual "VTT format".

If you also wanted to create tokens, elements, etc., for use in VTT, those would need be in .PNG format with a transparent background.

Take a look at these videos from Roll20. They'll give you a better understanding of what VTTs are, how they work, what they can do, etc.
Roll20 GM Overview
New Player Overview
Roll20 -- Grid Alignment Tool

[anstett]

Looking in on this very late but to echo what has been said.

No grid makes for a good VTT map.

JPG makes for a quick easy transfer.

PNG makes for nice icons/tokens

One thing is to offer the tokens at a lower resolution also. Loading up a map then tossing 10 tokens on it plus the Player Icons, etc can really slow down transfer times - especially over DSL speed connections

The above examples would be fine for battle maps in a VTT if they did not have the grid on them.

BOB

[Xorne]

I agree with the advice here. The desired image size largely depends on which VTT you're using, too. I'd say between 50-100 pixels per square is good, and as long as it's a round number then players can resize it simply. MapTools easily has the most room for the map, and does well with 100 px/sq, while Fantasy Grounds 2 typically has the least dedicated map space, so I like 50 px/sq there. Roll20 is similar to MapTools, though a little more is covered up--but either way Roll20 defaults to 70 px/sq token-snapping.

Something you might do (especially with large maps) is offer an alternate version which drops the color count significantly to reduce file size. The Caves of Chaos (B2) map I'm making is 740'x500'. With a 5' grid that's 3700x2500 just at 50 px/sq! Granted, if you're making battle maps it's not as big a deal, but for a dungeon-roam where you want the whole map, you can save a lot of file-size by dropping the color palette without losing much on the image.