Creating good maps for use in roleplaying is a favorite pastime for many DMs. The proliferation of online virtual tabletops has made the creation of digital maps an interest that many folk pursue to aid in their own campaigns.
Most maps that come with role-playing supplements have those nice little grid lines that seem to blend into the image and aid you in gauging distances in your combat encounters.
This quick tutorial will show you how to make a grid layer that will fit any size map you wish to create.
First things first... fire up your image editor of choice... I'll be using photoshop for this tutorial but, the technique is simple enough to be applicable to most graphics manipulation programs.
You will need decide on a pixel width for each square in the grid first.
For this lesson, we'll create a 45px grid overlay.
note: That would mean a 10x10 square map would turn out to be a 450x450 px base image
1: Create a new file with a length and width of 45px and in the RGB colorspace.
2: Create a new layer and fill it completely with a solid color... I prefer to use black but, other colors would work, it's a moot point really when you get to color overlays and such.
3: Either use the Magic Wand tool to select the entire image or just use a marquee select to draw a selection that spans the entire image. Here's where it gets tricky... Just kidding...
4: Using the arrow keys, move the 'selection' 1 pixel to the right, and 1 pixel down.
((for a thicker line on your grid, move two pixels in each direction instead))
5: Once you have moved the selection, use Cntrl-X to cut out the selected area.
You should now have a single black line that runs along the left and top edges of the image. The area you cut should show the white background layer behind it.
6: Take the background layer and either delete it, or just hide it.
7: Save your selection as a new pattern titled '45pxGrid' or some other easy to remember name.
8: Now, open a new file. For best results, make the file's dimensions a multiple of your chosen grid size. In this case, we went with a 45px grid so, we're going to create a file that is 450x450 px.
9: Create the new file and add a new layer.
10: Choose your Fill tool and set it to fill with a pattern.
11: Find your newly created pattern and select it.
12: Then simply click on the new layer you created to fill it with the pattern.
A nicely formatted grid should show up over the whole image. The grid will line up for most Virtual Tabletop's grid properties with little to no error.
You can also tweak the colors and thickness of grid using layer properties and such to achieve some nice effects like indenting into the floor to make a tile like blend or whatever wlse you can think of. I usually turn the opacity of the layer way down and use it as a guide for positioning objects and features.
You can also use the selection tool later on to clip out various areas of the grid and keep it limited to your dungeon floor to create a more professional look. ((This is great for VTT's because you can set their grid to match the lines on your map but, you make the VTT's grid transparent and instead only see the grids on your map...))
Anyway, if you think I need to add images to this to make it clearer, let me know and I'll post some. if any of the directions are unclear, please let me know. If anyone has any Gimp specific references they'd like to add... please do so.