(EARTH-LIKE) PLANET GENERATOR

To launch the generator, just open planetz.html in your favorite (not IE please) browser. Loading can take a while (perhaps up to a minute). If the browser prompts you to kill the page, click wait; it will eventually complete.

After the page loads, you can also scroll down to see the generated perlin noise and the texture applied to the planet.

How does it work

1. Generate perlin noise. For this I used a script I found online, that I adapted to also use octaves.
2. Process perlin noise:
   1. Normalize between 0 and 1; by default the algorithm produces noise mostly in the range (0.45, 0.75).
   2. Apply non-linearity to noise. We apply a variation of the tanh function to suppress lower values (which will constitute water later in the process). This way we have nicer looking coast-lines, as opposed to smooth transitions between water and land.
   3. Apply edge blur. Since we project the texture onto a sphere, land on opposite sides of the texture will look different. Blurring helps blend better.
   4. Pad on top and bottom to avoid projection artefacts (this is only a work-around rather than a solution to projection).
3. Generate texture from the resulting height-map:
   1. We designate a minimum threshold under which everything is considered water. We place snow on the highest 0.5% of points and stone on the highest 3%. The rest is earth for now.
   2. Add a bit more entropy: pick N points on the map; if these points aren't on water, perform a flood fill around them with threshold eps. If the filled area is big enough, transform it randomly into another ground type (snow, water or stone).
   3. Color the resulting terrain: for each terrain type we calculate its color as a function of altitude. For example, for stone, the higher up it is, the lighter the color. We then apply a bit of noise.

Parameters that can be tuned

Perlin noise

• Number of octaves and their amplitudes

Generation:

• Size of canvas
• Resolution
• Slope of non-linear function applied to the perlin noise
• Edge blur radius and padding size

Texturing:

• Water, snow, stone prevalence/level
• Flood fill N and eps values (note: the higher the resolution, the lower eps should be)
• Chosen colors for each terrain type and randomness applied to the color