There are changes occur to the terrain over time.
- Plate tectomics
- Hydrolic: caused by water
- Pneumatic: caused by air
- Thermal: caused by heat
- Lime + water
The basic result of hydrolic erosion is that land drains.
In the new heightmap, find the lowest elevation, which is defined as:
- each pixel.height >= original
- each pixel.height > at least one neighbor .height
- except the drains
Speed of Water
Generally speaking, the faster the water is, the more erosion there is.
The flat area does not erode, and the slopes erode fast, so the result is very steep cliffs.
- Small amount of water everywhere (raining)
- Have water move down
- Erode as water moves (based on the slope and amount of water)
How water affects the terrain?
- Carries sediment
- Amount of sediment kinetic energy
At turning of a river, the outside of the curve gradually gets larger, while the inside does not grow.
When water erode away dirt/rock near the river bed, rocks become hang by itself on the bank. When the erosion reach some threshold, the whole piece of land will slide down.
When there are plants, wind erosion does not affect the land.
When there are no plants, wind will blow away pieces over time, and forms round shapes on the rocks.
Wind blows slower close to surface. So if there is a large flat ground, wind erosion will be less severe. When there is sharp curves, there is not enough length to slow down, and thus causing faster erosion.
Heat causes expansions, and coldness causes contraction. Rocks are rigid, not malleable, and thus the expansions/contractions will cause microfractures on the rocks, which will grow larger over time.
Crystallized Fracture Plains
Slow, high pressure deposition yields organized forms.
Lime + Water
When Height Map Fails
A voxel is a volume of pixels. 3-D array of pixels.
In each pixel, there are some fraction of rocks vs air.
Spheroidal Weathering: Pneumatic + Thermal - Smoothing effect
For each pixel, if neighbors have more rock than itself # low concavicity less weathering else more weathering based on the pixels with lower rock
if the function of concavicity and weathering is good, the weathering tends to create a sphere.
Marching Cubes Algorithm
The goal: Turn voxels into polygons
Connect the center of each cell -> a set of cubes
Determine whether each cell is inside rock or not, and based on that select a model of cube. Each model marks some boundary of the shape.
A set of points along the border of air and rock. Calculate angle of neighboring points, and figure out how to move the pixel.
- Poor Spacing
- Topology changes, A non-hole shape -> a hole shape
Power Snail COMSCI
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