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Thread: Map projection and Erosion (Wilbur-like)

  1. #1
    Guild Member Gallien's Avatar
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    Question Map projection and Erosion (Wilbur-like)

    I am thinking of making a world map (a heightmap) and editing it in Wilbur (adding erosion, riverstreams etc.).

    If I use a projection like Mercator or Equirectangular, Wilbur definetly won't understand it. The rivers will be the same from Wilbur's point of view, but in fact Wilbur will make real, large rivers only near the equator - the polar "rivers" will be more like little streams in the mud after a summer rain. 5 pixels near the eqator are not equal to 5 pixels near the poles. So I will probably need to use an equal-area projection to avoid that. The distortion of angles will happen, but it is not that problematic... right? Actually I am not sure I am right here...

    On the other hand - may be the map should be cut into several pieces for separate editing? The equatorial cyllinder and the polar circles? Then those parts will have to be merged later and the problem of dealing with the stitches rises.
    Probably cutting the map into pieces is a better solution because it will allow you to apply different erosion settings in different regions - but, once again, what about the stitches?
    It seems the river map is probably going to be terribly distorted... (If you "cut away" the upper part of the river Wilbur will never know it existed.)

    The perfect solution would be combining best from both worlds - finding a good projection for rough editing of the global map, and then finding a good solution for the problems that rise when you polish the map region by region.

    Has somebody already faced these problems? All the Wilbur tutorials I read do not cover the issue with projections or cutting maps into pieces and sewing them together again (or at least do not concentrate on them).

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    Guild Member Gallien's Avatar
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    Probably equal area projections are better for precipitation-based erosion effects, while conformal projections (Mercator and others, which preserve angles and directions) are better for incise-flow erosion (riverbeds)? The whole idea seems hopeless on a global map, but even when making regional maps you have to think about minimizing the distortions at the borders of the regions (if you want to combine the regions later). On the other side, when an image is reprojected it probably loses definition (I do not know how strong is that effect). So even if this is this projection change helps a bit to adjust the map parts in theory (though I'm not sure about it) - it could be impossible to implement practically...

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    Guild Expert johnvanvliet's Avatar
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    what i do is map 70 north to 70 south in Mercator
    then 90 north to 60 N or 45 N ( and the southpole ) to polar-stereographic
    run the two poles and the center at the SAME settings in wilbur

    then remap all 3 back to simple cylindrical and blend them
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  4. #4
    Guild Member Gallien's Avatar
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    Thanks, johnvanvliet!
    Now I'm reading wikipedia articles on plate tectonics but soon I'll start drawing the map itself.

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