A small demonstration of how to make an outer space map. The mod includes a tileset and some map blocks which use it, and it applies them to the POLAR tileset. You can thus play it in-game by going to any POLAR map, or running a quick battle on POLAR tileset.
The MCD file includes several floor tiles which look like a starry backdrop, plus several object tiles which look like individual larger star formations. These are collated together to make a map block with a randomized arrangement of floor tiles plus a random smattering of object tiles. The map script then fills the map with a random assortment of map blocks. When done right, this gives the ground a tile-less "space" look.
Getting it to look right is a lot trickier than it appears at first glance, but if you follow my tips here, you should be able to make these sort of graphics yourself easily!
A.) To make the starry backdrop, you can start by drawing dots of varying brightness in a sort of random distribution across the floor area of the tile. But what you'll quickly find is that your tile looks way less random than you'd hoped once you put it together with others. You can see this easily in Volutar's MCDEdit if you use the option to view your tile arranged together nine times in a 3x3 grid. It's easier to make the graphic look even when using a tool to see it tiled like this, but the real trick is to understand how your mind naturally defaults to putting more stars in the main area and less toward the edges, and especially less toward the corners. To truly randomize the star placement, you have to practice compensating for this innate bias.
B.) Once you have the hang of making starry floor tiles, you'll want at least a few different tiles. If you just tile the same piece across the entire mapblock, your mind will easily spot the repeating pattern. But with 4+ versions that differ from each other, you can make a random-ish arrangement across the mapblock which will look to your mind's eye as though it were a random assortment of stars. The trick, then, is to ensure that the concentration of stars in each different tile is roughly the same. If one tile is significantly fuller than another, your mind will catch the difference and it'll break the illusion.
C.) Adding a bit more than just little stars is a great way to flesh out the stellar backdrop and make it look more interesting. I made some colored star clusters, but you could add nebulae, galaxies, planets, or other interesting things. If you want to put in a lot of effort, you can make large pieces of artwork which can be tiled together manually in the map blocks, to add impressive visuals such as great big planets, nebulae, or galaxies across the backdrop. I just did some easy small doodads. Now the way I put the doodads in was to add them as objects, so that they sit on top of the starry floor tiles. The advantage of this method is that you can easily have varying combinations of doodads with star tiles, but the disadvantage is that it breaks immersion slightly by occluding the selector cursor in-game. To avoid ever occluding the selector cursor in-game, your doodads have to be merged with the floor (they must be made out of floor tiles, with the star backdrop merged with the doodad), and this can increase the workload involved in trying to mesh them well enough with the background to avoid repeating patterns showing up.
D.) You'll want to have at least a few "random" map blocks with an assortment of stars and doodads. I only made four of them, but it works well because I carefully balanced the total doodad coverage to avoid any one type dominating over others. There's plenty of ways to make it look good, but having more random blocks is one of the best ways to go. Your map script should place any special blocks how you want them first, and then fill in the remaining spaces with a random assortment of the "random" blocks. It may help to limit the amount of each "random" block able to be placed, but be careful not to over-limit them or else your map may wind up crashing the game due to not having enough blocks to finish generating.
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If this tutorial is too advanced for you, then check online for tutorials for map and/or mcd editing, or ask in the Open X-Com Discord channel.
If you aren't interested in making your own maps, then feel free to use mine! For proper integration into your mod, you'll still want to create a new tileset and add it either to specific deployments or somewhere on the globe. Otherwise, if you just plug in my mod, you'll just wind up in space every time you run a polar mission!
Feel free to comment here, but I may be slow to reply. It is faster to contact me on the forums, and fastest to contact me on Discord.
Forum link: Openxcom.org
Discord link: Discord.gg