Update

procgen.md

@@ -27,7 +27,7 @@ Indeed we may also do something "in between", e.g. generate procedural assets in
 
 The following are some techniques and concepts often used in procedural generation:
 
-- **[noise](noise.md)**: Noise is often used as a basis for generation or for modulation, it can be seen as kind of "RNG taken to the next level" -- noise is greatly random but also usually has some structure, for example it may resemble smoke or water ripples. There are great many types of noise and algorithms for its generation; the simplest [white noise](white_noise.md) is actually not very useful, more common are various forms of fractal noise, often used noises are [Perlin noise](perlin_noise.md), [simplex noise](simplex_noise.md) etc., other ones are [Voronoi](voronoi.md) diagrams, midpoint displacement, spot noise, cosine noise, fault formation etcetc.
+- **[noise](noise.md)**: Noise is often used as a basis for generation or for modulation, it can be seen as kind of "RNG taken to the next level" -- noise is greatly random but also usually has some structure, for example it may resemble smoke or water ripples. There are great many types of noise and algorithms for its generation; the simplest [white noise](white_noise.md) is actually not very useful, more common are various forms of fractal noise, often used noises are [Perlin noise](perlin_noise.md), [simplex noise](simplex_noise.md) etc., other ones are [Voronoi](voronoi.md) diagrams, coin flip noise, midpoint displacement, spot noise, cosine noise, fault formation, Brownian motion etcetc.
 - **[random number generators](rng.md)**: To make random decisions we use random number generators -- here we actually don't have to have the best generators, we aren't dealing with "security" or anything critical, however the generator should at least have a great period so that it's not limited to just generating few different results, and its useful to be able to choose [probability distribution](probability_distribution.md).
 - **[modulation](modulation.md)**: Using previously generated procedural data, for example noise, to somehow affect another data -- for example imagine we already have some basic procedural texture but want to make it more interesting by randomly displacing its individual pixels to warp it a little bit. If we use a simple random number generator for each pixel, the result will just look too chaotic, so it's better if we e.g. use two additional Perlin noise textures, which together say for each pixel by what distance and angle we'll displace the pixel. As Perlin noise is more continuous, gradual noise, then also the distortion will be kind of continuous and nice. A famous example of this is marble texture that can be generated by horizontally modulating a texture of vertical black and white stripes with Perlin noise.
 - **simulations resembling natural/biological phenomena**: E.g. [cellular automata](cellular_automaton.md), [particle systems](particle_system.md), erosion simulation, [agent systems](agent_system.md) (letting virtual "workers" collaborate on creating something) ...