FT3+ Can I Customize Equal Earth Projection?

Hi!

I'm messing with Fractal Terrains 3+ to help create a new world map for my fantasy RPG setting, and I want to view and export the map in Equal Earth projection, but extending to the poles. In FT3, that projection cuts off at +/- 75 degrees longitude, so any polar landmasses get clipped, and mid-latitude stuff looks more extreme N/S than usual.

I found the projections file and the instructions on creating new projections, but I can't see a way to change the parameters of an existing projection or to define a new one that isn't just segments of an existing one. Ideally, I'd like to be able to copy-paste the code for the EE projection and edit it.

Does anyone know a way to make your own projections that aren't just segments from existing ones? Or is there some other way I could get the results I'm looking for?

Thanks!

Best Answer

  • jslaytonjslayton Mapmaker Moderator, ProFantasy
    Accepted Answer

    Thank for reporting the Equal Earth projection bug! It looks like I did something wrong when I ported the code, probably in the vertical scaling factor. I'll try to get that fixed in the next update. There isn't a way to patch that until then.

    Interrupted projections as defined in Projection.txt are only defined in terms of the projections that FT already has built into the program. There isn't a way to add a new built-in projection without a new program version.

    I'm not sure what you mean by "change the parameters of an existing projection" with regards to the projections. Can you elaborate?

    Joel MLoopysueroflo1

Answers

  • jslaytonjslayton Mapmaker Moderator, ProFantasy
    Accepted Answer

    Thank for reporting the Equal Earth projection bug! It looks like I did something wrong when I ported the code, probably in the vertical scaling factor. I'll try to get that fixed in the next update. There isn't a way to patch that until then.

    Interrupted projections as defined in Projection.txt are only defined in terms of the projections that FT already has built into the program. There isn't a way to add a new built-in projection without a new program version.

    I'm not sure what you mean by "change the parameters of an existing projection" with regards to the projections. Can you elaborate?

    Joel MLoopysueroflo1
  • edited January 12

    Thanks for the answer! I've seen you on previous discussions I found while searching various FT questions and knew I was probably getting an answer when I saw your username on the notification.😄

    Glad to hear it's a bug. I had assumed it was either an intentional choice or some necessity of the projection math and spent a good bit of time squinting at other EE projections I found online to see if it was impossible to show poles or something.

    By "change the parameters of an existing projection", I meant defining a new one based on it that had a different area of interest. I attempted this yesterday and just got the same results:

    Projection 128, "Equal Earth Poles"
    // i can't tell what extent does. Extent -100, 100, 100, -100
    Scale 1.0
    Description "Equal Earth with Poles"
    
    Segment "Equal Earth", 0, 0, 0, 0, 1, 0, 0
    scale 1, 1
    Offset 0.0, 0.0
    Effective -180, 90, 180, -90
    Rotate 0
    EndSegment
    
    EndProjection
    

    At the risk of turning this into a projection file Q&A, you can see a note there from when I tried to get rid of the wide black margins around the map at "Zoom Extents" by messing with the Extent, but I couldn't figure out what units "screen-space extents for the projection" used and didn't get anywhere.

    I was also considering just adding orthographic or stereographic poles as separate segments floating nearby. An alternative I've been thinking about today but haven't tried yet is finding another projection with poles, then splicing those in as two more segments and trying to line them up.

  • jslaytonjslayton Mapmaker Moderator, ProFantasy

    Extent is the screen-space extents for the projection and defaults to -1, -1, +1, +1 if I recall correctly. It is how much of the screen area (that -1, -1, +1, +1 space defined above) that your projection will occupy. For most projections, this value will be some multiple of pi. The whole-projection Scale (not the per-segment Scale) is a scaling factor that deals with the same space. Depending on what you're doing with the projection, you may or may not need to specify these values. As an example, look at Projection 89, "Wagner Stereographic Endcaps" and Projection 89, "Wagner Stereographic Endcaps". Those projections also have little Stereographic pole pieces nearby.

    I really probably ought to have defined the projections in terms of meters and other real-world units, but I was young and stupid back then. Now I'm old and stupid, which is quite a different experience.

    Joel M
  • jslaytonjslayton Mapmaker Moderator, ProFantasy

    It turns out that 1.3173627591574 is not pi/2...

    Joel M
  • 1 month later
  • edited February 11

    Today I took a break from climate stuff and made a multi-segment projection as a workaround until the fix arrives. Not sure what it will do to CC3+ export, but it lets me see the poles in a similar (but not identical) projection without an obvious seam unless you zoom real close. In case anyone else has the same problem, this goes in Projection.txt:


    Projection 128, "Equal Earth Poles"
    Scale 1.0
    Description "Equal Earth with Wagner Poles"
    
    Segment "Equal Earth", 0, 0, 0, 0, 1, 0, 0
    scale 1, 1
    Offset 0.0, 0.0
    Effective -180, 90, 180, -90
    Rotate 0
    EndSegment
    
    Segment "Wagner IV", 0, 0, 0, 0, 1, 0, 0
    scale 0.978, 0.978
    Offset 0.0, -0.0559
    Effective -180, 90, 180, 75
    Rotate 0
    EndSegment
    
    Segment "Wagner IV", 0, 0, 0, 0, 1, 0, 0
    scale 0.978, 0.978
    Offset 0.0, +0.0559
    Effective -180, -75, 180, -90
    Rotate 0
    EndSegment
    
    EndProjection
    


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