How do I create the sphere-distortion on an 2D map?

[Krautpotato]

I cannot get my head around how I can make my equirectangular map look good on a spheric-projection.

You can find both screenshots here:
https://imgur.com/a/JmYl2GH

[Chashio]

It can be a little tricky. The poles on an equirectangular map spread across the entire width of the image, so you have to significantly stretch the map as you get close to the poles. You could just warp it with a transform tool and it would end up looking more like this...
Krautpotato world equirec-stretch.png Krautpotato world equirec-stretch pole.png

Or... What software are you using? In Photoshop 4 on, you can actually create a 3D sphere from a layer and paint on it. And there's probably a more direct approach in newer versions or CC. There may be a way to do so in Blender as well but I don't know it. There might be a way to do that in GIMP, I vaguely recall putting an early map on a rotating globe like ten years ago before I got Photoshop, but I'm not sure I ever painted on it.

[J.Edward]

I am moving this over to the How Do I forum

[waldronate]

You need to understand the basics of map projections. There are lots of discussions on the Internet, so I recommend a few moments with your favorite search engine using the term "map projections".

You drew something. What was its map projection? Many people draw something on a map that they treat as a flat map and then, some time later, want to put it onto a globe. If you didn't start with an appropriate map projection, then retrofitting one later on is a very hard (certainly time-consuming) problem.

For purposes of discussion, I'll assume that you drew a map and now you want to put that map onto a globe. You heard somewhere that Equirectangular is a good projection to put onto a globe, so you declared your map as being Equirectangular, but it got distorted when put onto a globe. Your first step is to decide how much distortion is acceptable. In this case, there is more distortion than you seem to want.

The least-work option is to accept the distortion as it is. It may not be what you particularly want, but you might learn to live with it.

The least-distorting option to get an Equirectangular map will require you to learn some GIS software or other. Then pick a projection for each landmass on your original map that minimizes distortion in an acceptable way for you (you might want to chop up overly-large landmasses into multiple maps). Search for "picking a map projection" in your favorite search engine for assistance with picking a suitable projection. Use that GIS software that you learned to reproject each piece to an Equirectangular map. Then assemble them together using some paint program equivalent to get your final image.

A middle-work option might be (as Chashio suggests) to get a piece of software that lets you paint onto a sphere. The simplest sphere UV mapping in most software packages is functionally equivalent to an Equirectangular projection, so that simplifies things. Now draw your map onto the globe. Your demonstrated drawings shouldn't take a huge amount of work to do that for.

The Equirectangular projection is a terrible one for humans because it doesn't preserve shapes, distances, or areas. It's very easy to construct and easy for computer to work with, though, which is why you see it a lot. A 3D globe is a good one for humans, but only if it's a physical globe and not a 2D Orthographic or similar projection. The physical thing is hard for a computer to work with, though.

As an aside, why did you draw the map? Why do you want to change its projection? Are you trying to measure things for storytelling purposes? Is it just practice to work with maps? Those questions seem frivolous, but they underlie your original request in a very real way.

[Krautpotato]

Okay, sorry for the late reply I didn't get any notfications.

I am using Photoshop CC 2019 and will probably try to draw on a 3D sphere here to make stuff look a little bit more realistic and un-distorted (?).

The purpose of this map is to get an idea of the whole world I am setting up for my novel, which I want to write in a few years (after the worldbuilding is done). So it's more like an orientation for me as well as a referring point for measurementt (distance etc). Most of the novel will play on only one continent so a world map isn't really needed but I imagine a larger world and want to make it at least kind of realistic from the beginning.