Cleanup various repository documentation files

- Reformat logo license as a plain text file.
- Fix outdated links or references to SFC or Visual Script.
- Tweak contents of `CONTRIBUTING.md` to highlight contributor docs more
  prominently, and make it easier to parse.
- Tweak formatting and contents in `thirdparty/README.md` for consistency.

1 files changed, 0 insertions, 27 deletions

diff --git a/thirdparty/cvtt/etc_notes.txt b/thirdparty/cvtt/etc_notes.txt
deleted file mode 100644
index bb041a8435..0000000000
--- a/thirdparty/cvtt/etc_notes.txt
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-The ETC1 compressor uses modified cluster fit:
-
-Assume that there exists an ideal base color and set of selectors for a given table.
-For a given table and set of selectors, the ideal base color can be determined by subtracting the offsets from each pixel and averaging them.
-Doing that is equivalent to subtracting the average offset from the average color.
-Because positive and negative selectors of the same magnitude cancel out, the search space of possible average offsets is reduced: 57 unique offsets for the first table and 81 for the others.
-Most of the offsets result in the same color as another average offset due to quantization of the base color, so those can be de-duplicated.
-So:
-- Start with a high-precision average color.
-- Apply precomputed luma offsets to it.
-- Quantize and de-duplicate the base colors.
-- Find the ideal selectors for each base color.
-
-Differential mode is solved by just finding the best legal combination from those attempts.
-
-There are several scenarios where this is not ideal:
-- Clamping behavior can sometimes be leveraged for a more accurate block.
-- Differentials can sometimes be moved slightly closer to become legal.
-- This only works when MSE is the error metric (i.e. not normal maps)
-- This only works when pixel weights are of equal importance (i.e. not using weight by alpha or edge deblocking)
-
-T and H mode just work by generating clustering assignments by computing a chrominance line and splitting the block in half by the chrominance midpoint and using those to determine the averages.
-
-Planar mode is just solved algebraically.
-
-If you want to emulate etc2comp's default settings, add the flag ETC_UseFakeBT709 to use its modified Rec. 709 error coefficients.
-Doing that will significantly slow down encoding because it requires much more complicated quantization math.
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