Help with converting maps

[Graceheart the Leopard]

I've been wanting to convert maps from Chris Wayan's World Dream Bank into Civilization maps. However, I've run into problems with the projection:

So I'm assuming that Wayan is using some sort of variation of the Mollweide or Robinson Projection in order to make his maps. How can I make a map of this without cutting off the edges?

 

[Blue Monkey]

What problems are you running into? How are you trying to convert? What do you mean by cutting off the edges? Can you provide a link to the source maps?

 

[Graceheart the Leopard]

The problem is, the projection has a large blank space at the corners of the map, and I'm not sure how to get rid of them without cropping the map. I need to know how to convert this into a projection that doesn't leave large blank spaces at the corners.

 

[Yoda Power]

I never heard of anyone changing a projection of a map. I assume no square version of your fantasy map exists?

 

[Graceheart the Leopard]

Nope.

 

[Blue Monkey]

Converting projections while maintaining as much accuracy as possible is a fairly complex process. Fundamentally you are distorting one 2d projection of a 3d surface into a completely different 2d projection.* To approximate that in the simplest way rescale in one dimension until the sides of the map itself are almost straight. Then rescale in the other dimension until it's approximately the shape you want. In doing so you're going to need to crop some of the polar regions.

* from Mollweide to Miller ( similar to biq geometry):

 

[Blue Monkey]

I spent the last 2.5 hours trying to use gimp's shear, perspective & scaling tools on the map. The goal was to split and transform sections then create a composite image. Can't come up with anything satisfactory. I can only think of the following ways to get a reasonably good looking transform:

1. Cut the map into really small pieces & manipulate the pieces in a progressively exaggerated way. Doing so with on the magnitude of a 100 pieces would be tedious and time consuming.
2. Find software or someone with the skill to place the map as the skin on a sphere & then slice it off as a new projection.
3. Do a compromise crop. Lose the polar regions. Crop a bit from the sides leaving some of the black. Try to do the cropping in a way that mostly loses water areas. Fill in the black with terrain by hand.
4. Cut and paste chunks of the map to compress the water areas - shifting the center edge toward the middle in the process.

The third choice is the quickest way. OTOH if I was doing it for my own mod I'd probably do it the fourth way - more time but better results. By the time you reduce the map to the scale of a game map the compromises may not make much difference. If you use BMPtoBIC 1 pixel in the original image equals one tile on the biq/map.

 

[Blue Monkey]

This should give you an idea about how complex choice 1 above is. I'm working on a similar transformation of a map of Barsoom - which is mostly empty desert so there's a lot of empty space that can be ignored while transforming sections with other terrain. The current state of the file has almost 70 layers and I'm only working with half of one hemisphere. Here's a screenshot of the visible layers next to Wayan's image so you can see the complexity involved. You would be transforming every quadrangle to be as close as possible to the shape of the central four, then putting it back together.

 

[Graceheart the Leopard]

You know, I'm beginning to wonder if I should just ask Wayan if he could draw any maps of his worlds in a cylindrical projection.

 

[Blue Monkey]

If he has then converting them would be straightforward. I've had his site bookmarked for a while. There are a lot of his maps that would be interesting to convert.