Ex Nihilo VIII: Pressure

Pressure is easily defined based on latitude and the presence of landforms. The rules are defined based on posts from here.

July

January

These parts aren't very exciting. But they're helpful as a public log of my progress.

Pressure II

Update from here.

This time around, since I'm avoiding all manual input as much as possible, I can programmatically generate the pressure bands, at least a rough approximation of them.

The first step is pretty simple, I just apply the rules from this post to hexes which meet the correct criteria.

Then to smooth it out, I apply a box blur with a radius of 10 hexes to the pressure values (which are scaled between -1 and 1). I do this 3 times to approximate a Gaussian blur. Since I'm doing this on a hex grid, I haven't yet figured out any of the clever optimization tricks that are available for this approximation on a square grid.

January (winter in the north)

July (summer in the north)

For my next trick, I will try to avoid memory leaks while calculating wind flow.

Pressure I: Under Pressure

The pressure systems of Earth are deeply complex, as as the winds they generate.

All I need to know is that wind flows from high points to low points and is affected by the Coriolis Force.

Easy to say, easier to implement. I used the guide here to set my initial pressure map, then used Inkscape to transform that into SVG paths. I was at a loss at first when thinking about how to take a gradient map and turn it into a wind flow field, but then I realized that I could just discretize the paths (black to white for low to high) and "walk" along the edge of each one. That would give me a rough outline of vectors for my winds. Its rough, it's not the 20-mile level of detail I'd want, but it's computationally cheap (not a simple thing (on my middle tier machine) if I were to use 200k objects), and it gets me what I want.

Both the "summer" and "winter" maps are considered, as the pressure is distributed differently during each macroseason. For most of the climate-related stuff, I'll have two maps, one for each macroseason, because of the way that the climate classifications are usually defined.

Pressure map for July (or "summer")

Wind map for July (or "summer")