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Misa 1f5835c985 Fix fade volume durations being incorrect 
The previous fade system used only one variable, the amount of volume to
fade per frame. However, this variable was an integer, meaning any
decimal portion would be truncated, and would lead to a longer fade
duration than intended.

The fade per volume is calculated by doing MIX_MAX_VOLUME / (fade_ms /
game.get_timestep()). MIX_MAX_VOLUME is 128, and game.get_timestep() is
usually 34, so a 3000 millisecond fade would be calculated as 128 /
(3000 / 34). 3000 / 34 is 88.235..., but that gets truncated to 88, and
then 128 / 88 becomes 1.454545..., which then gets truncated to 1. This
essentially means 1 is added to or subtracted from the volume every
frame, and given that the max volume is 128, this means that the fade
lasts for 128 frames. Now, instead of the fade duration lasting 3
seconds, the fade now lasts for 128 frames, which is 128 * 34 / 1000 =
4.352 seconds long.

This could be fixed using floats, but when you introduce floats, you now
have 1.9999998 problems. For instance, I'm concerned about
floating-point determinism issues.

What I've done instead is switch the system to use four different
variables instead: the start volume, the end volume, the total duration,
and the duration completed so far (called the "step"). For every frame,
the game interpolates which value should be used based on the step, the
total duration, and the start and end volumes, and then adds the
timestep to the step. This way, fades will be correctly timed, and we
don't have potential determinism issues.

Doing this also fixes inaccuracies with the game timestep changing
during the fade, since the timestep is only used in the calculation
once at the beginning in the previous system.
2021-04-27 20:33:44 -04:00
.github Remove 2.3 example from pull request template 2021-03-24 14:36:33 -07:00
desktop_version Fix fade volume durations being incorrect 2021-04-27 20:33:44 -04:00
mobile_version Fix 1x1 quicksand collision optimization not working 2020-05-13 08:16:34 -04:00
third_party Remove TinyXML-1 2020-06-12 15:08:29 -04:00
tools Adding original mapping tools for the sake of completeness 2020-01-12 19:49:24 +01:00
.gitattributes fix actionscript misclassified as angelscript 2020-01-12 15:18:45 -05:00
License exceptions.md Update License exceptions.md 2020-11-23 16:33:54 +10:30
LICENSE.md Updated link to Make and Play edition 2020-01-13 19:37:50 +01:00
README.md Update README.md 2020-01-10 17:45:29 +01:00

README.md

This is the source code to VVVVVV, version 2.0+. For more context about this release, see the announcement on Terry's blog!

License

VVVVVV's source code is made available under a custom license. See LICENSE.md for more details.

In general, if you're interested in creating something that falls outside the license terms, get in touch with Terry and we'll talk about it!

Authors

Versions

There are two versions of the VVVVVV source code available - the desktop version (based on the C++ port, and currently live on Steam), and the mobile version (based on a fork of the original flash source code, and currently live on iOS and Android).