Using gplates for Realistic Worldbuilding

I was “recently” introduced(re-introduced as I already had an older version) to gplates in a world mapping thread on the sfrpg forum.

There’s some good stuff in that thread. Ishmael’s gimmick for baking planet surface texture maps in Blender is very useful even if it does retain the weaknesses inherent to any automated noise-based mapping tool. Beech has some nice maps genned up in LunarCell(again, automated noise-based generation, but purdy nonetheless).

Later, I posted about gplates in a thread on the Zompist board about Programs for Drawing on a Sphere. This program is perfect for that, even without the fun plate rotation transforms.

First you need to download gplates for your system. Windows, MacOS(10.5+) and Ubuntu Linux binaries are available here as is the sourcecode. Once you have the program, let’s get down to business.

We’ll start with the simplest case. Drawing on a sphere.

Set the projection to 3D Orthographic. This should be the default, but failing that click on the View menu on the main menubar and select Set Projection…(hereafter described as View>Set Projection…). This will open a small window as shown below.

View>Set Projection...

View>Set Projection…

In the Projection submenu, the options available are: 3D Orthographic, Rectangular, Mercator, Mollweide and Robinson. Select 3D Orthographic. This projection allows you to maneuver the view rotation in a manner similar to Google Earth, so that you can center the projection in the location where you are working. For clarity I’ve chosen a view of the Earth to demonstrate.

A view of Earth in the 3D Orthographic projection. Whoooh!

A view of Earth in the 3D Orthographic projection. Whoooh!

Now in the leftmost toolbar on this main screen there are six options, in order from top to bottom: View, Feature Inspection, Digitization, Topology, Pole Manipulation and Create Small Circles. In the hopes of salvaging some semblance of brevity, I’ll only be using tools from, View, Digitization and Pole Manipulation in this post. Well. Hopefully, I’ll get to pole manipulation…

If you select the View option from the leftmost toolbar(let’s call it the Tool Palette), you will see two tools in the sub-palette above and to the right of the Tool Palette. These are, from top down: Drag Globeglobe_rotation_35 and Zoom Inglobe_zoom_35 If you hold down shift while dragging with Drag Globe, the view will rotate around the center of the view. If you hold down shift while clicking with Zoom In, you’ll zoom out. Play around with the view tools. When you figure you’ve got them worked out, come on back and keep reading.

Welcome back. Hopefully you had fun. Now we’re on to Digitization, the third category down the Tool Palette.digitise_polyline_35That’s also the icon for the Digitize New Polyline Geometry tool, that has its uses, but for now we’ll use a different tool. From the sub-palette select fourth tool down, Digitize New Polygon Geometry.digitise_polygon_35Now I’m going to assume you’re working on an empty globe. Dull, but ripe with potential. If not, check Window>Show Layers; in the resulting Layers window, click the bar to show options for any open layer, make sure Manage Layer is visible and click Delete Layer… Easy-peasy, lemon squeezy. Now let’s draw some continents!

Using Drag Globe from the View tool category, center the view on the area where you want to draw your first continent. I’m going to start with a continent on the north pole. Up there where pinching is usually an issue. Using that Polygon Geometry tool in Digitization draw a blob one point at a time to make a nice shape for your continent. When you got a shape you like hit the Create Feature button towards the middle of the right edge of the window to close the polygon and start the process of saving your new continent.

For Feature Type let’s keep it simple and stay with gpml:UnclassifiedFeature. Click Next.

For the geometry’s purpose, Boundary should serve just fine, pick any old name you like. I’ll go with Arctica for this one. For reconstruction method, By PlateID is perfect and for this continent we’ll enter a PlateID of 1000 and leave the rest as is. We’ll deal with that stuff later. It’s related to Pole Manipulation, which I’ll probably save for the next post as this one’s getting a bit long. Just understand that all features you will be wanting to move together as a unit should have the same PlateID and sets of features you want to move independently will have different PlateIDs. By the way, let’s click Distant Past and Distant Future for appearance and disappearance times. Don’t worry about it yet… Click Next.

The next window we’ll leave be. You can play with it on your own later if you like. For now, click Next.

Now we choose a Feature Collection to associate our continent polygon with. Since this is a Blank New World, I’m going with <Create a new feature collection>. Hit the Create and Save button. This will open the Manage Feature Collections window.

Select the icon next to your New Feature Collection that looks like an old floppy disk with a pencil on it(Save As). Select a location and name for your feature collection file. I’ve decided to call this world Gamhang, so I’ll name the file Gamhang.gpml. You also can select a different format for your file. For some purposes an ESRI shapefile can be very flexible, but it may lack some elements that could prove useful later, so I’ll use the program-native gpml format.

Here’s the current state of my world in 3D Orthographic.

A 3D globe view of Arctica. Exciting...

A 3D globe view of Arctica. Exciting…

Same continent in the projection gplates refers to as Rectangular. Also sometimes referred to as geographic, latlong, plate carée, spherical or equirectangular. Widely useful in many apps.

Same continent in the projection gplates refers to as Rectangular. Also sometimes referred to as geographic, latlong, plate carée, spherical or equirectangular. Widely useful in many apps.

Pretty simple, so far. Below I have the same feature shown in the widely used equirectangular projection.

Just to add to the fun, I’m going to draw the axis of a mountain range across this continent.

This time I’ll use the New Polyline tool. I guess I could draw the closed polygon depicting the mountainous region, which would be useful in some applications, but lets play with a different tool this time.

This time I’m going to use the gpml:Topography type, not because it’s particularly suitable, but just to differentiate between continental boundaries and (approximate)mountain range centerlines. Give it the same PlateID as its associated continental boundary. In hindsight gpml:ClosedContinentalBoundary, gpml:ClosedPlateBoundary or gpml:Shoreline might have been better for the continental polygon…

Actually, topography seems to limit my possibilities for feature purpose to Outline, so I guess I’m stuck with gpml:UnclassifiedFeature. Damn. Okay, so we go back and use that. Set the purpose to centre line. I’ll name my feature Trans-Arctic Mountains. Make sure the PlateID is still 1000 and you’re good.

Add this to the feature collection you already made, and save.

Just to be complete, we’ll now create a new continent polygon with its own mountain range(s). Assign the PlateID 2000 to these features. I named my continent Tropica(for reasons that will become clear later) and drew it sort of contiguous with the edge of Arctica to begin defining some ancient pangaean Pangamhang continent. We’ll show how to get things separated later. I also created two mountain ranges inside the continent polygon, named, imaginatively, the West Tropican Mountains and the East Tropican Mountains. All of this I save to the same Gamhang.gpml feature set I previously used.

Now, if you had drawn things exactly as I had(neither likely nor necessary), and your

A Tale of Two Plates

A Tale of Two Plates

coloring is by PlateID(Features>Manage Coloring), your globe view could look something like this. Now, I think we have all the knowledge we need to pretty much place continents and mountains as we wish. We can play with other feature classes besides polygons and polylines. The multi-point tooldigitise_multipoint_35 can be used to denote cities or other map elements that approximate points at this small scale. The multi-point tool, for its part, is good for much more than mountains, it can be used, for example to delineate rivers or roads or other linear features. As already mentioned, the polygon tool can be used to create mountainous areas, or countries or other sorts of regions. I leave it up to the reader’s imagination to delve the limits of the tools. Also note the measure toolcalipers is a great way to check the scale of your features. Gplates is actually a somewhat decent GIS tool in its own right.

Here’s a tiny bonus. Let’s look at the Pole Manipulation category in the Tool Paletteafrica_pole_rotation_35. We’ll select the Choose Feature toolafrica_highlight_clicked_35 first to select the continent we want to move. Now we reselect the Modify Reconstruction Poleafrica_pole_rotation_35 tool. Drag the tool around on the globe and watch a little ghost of the pole movecontinent with all of its little subsidiary features(mountain ranges) move around on the globe. To make the actual polygon and the other associated features to the ghost location, click the Apply button, which is in the same location as the Create Feature button we pressed when digitizing the features. In this case, you’ll find that you can’t actually get the transform to apply. Consider this a preview of the next post,

Here is the pole transformation as seen in equirectangular projection. You will notice Tropica and both of its associated mountain ranges have moved(at least as ghosts. Arctica and all its bits stay put. This is important...

Here is the pole transformation as seen in equirectangular projection. You will notice Tropica and both of its associated mountain ranges have moved(at least as ghosts. Arctica and all its bits stay put. This is important…

when we make the magic actually happen. The process should be a good deal simpler than what we’ve already gone over, but more than I want to add to a post that already exceeds 1500 words.

Thank you,
The Astrographer

p.s. There’s a sequel to this post on getting the continents drifting. Enjoy!

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3 Responses to Using gplates for Realistic Worldbuilding

  1. Pingback: Continental Drift the gplates Way | Astrographer

  2. Pingback: The Four Elements: It’s all in the Record (continued) » Jeno Marz

  3. Pingback: WIP- unnamed fantasy world - Page 3

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