Ditherpunk: The article I wish I had about monochrome image dithering

Post by HanyouHottie » Thu, Jan 07, 2021, 1:18 AM UTC

aidenn0 wrote: post #89

zlsa wrote: post #30

Earlier quoted context omitted.

I believe this is what the engines are doing during the majority of the ascent of the Starship SN8 test vehicle[0]. You can see the engines gimbaling very slightly in a circular pattern. [0]: https://youtu.be/ap-BkkrRg-o?t=6516

Anything controlled by a PID can easily end up in a circular pattern, so it's not a given that this was to avoid stiction. [edit] 1 dimensional PIDs can end up in a sinusoidal dynamic equilibrium, and a 2 dimensional sine wave is an ellipse.

Post by rathel » Thu, Jan 07, 2021, 6:11 PM UTC

darusnna wrote: post #174

vanderZwan wrote: post #160

Earlier quoted context omitted.

I have no idea what those parameters represent, but I'm very curious! Could you give a layman's explanation?

The standard PRBS23 polynomial is X^23 + X^18 + 1. Most of the factors are zero. Only the factors for exp 23,18,1 are 1. This causes poor bit mixing - ie the output sequence will have strong correlation every 23 bits. Choosing a "fat" primitive polynomial, ie a polynomial not from this list[0] but rather a polynomial with 50% of the taps are 1 (but it still must be primitive[1]), increases the avalanche effect[2] to…