b8a4b4dfe7
I was investigating a desync in my Nova TAS, and it turns out that the gravity line collision functions check for the `oldxp` and `oldyp` of the player, i.e. their position on the previous frame, along with their position on the current frame. So, if the player either collided with the gravity line last frame or this frame, then the player collided with the gravity line this frame. Except, that's not actually true. It turns out that `oldxp` and `oldyp` don't necessarily always correspond to the `xp` and `yp` of the player on the previous frame. It turns out that your `oldyp` will be updated if you stand on a vertically moving platform, before the gravity line collision function gets ran. So, if you were colliding with a gravity line on the previous frame, but you got moved out of there by a vertically moving platform, then you just don't collide with the gravity line at all. However, this behavior changed in 2.3 after my over-30-FPS patch got merged (#220). That patch took advantage of the existing `oldxp` and `oldyp` entity attributes, and uses them to interpolate their positions during rendering to make everything look real smooth. Previously, `oldxp` and `oldyp` would both be updated in `entityclass::updateentitylogic()`. However, I moved it in that patch to update right before `gameinput()` in `main.cpp`. As a result, `oldyp` no longer gets updated whenever the player stands on a vertically moving platform. This ends up desyncing my TAS. As expected, updating `oldyp` in `entityclass::movingplatformfix()` (the function responsible for moving the player whenever they stand on a vertically moving platform) makes it so that my TAS syncs, but the visuals are glitchy when standing on a vertically moving platform. And as much as I'd like to get rid of gravity lines checking for whether you've collided with them on the previous frame, doing that desyncs my TAS, too. In the end, it seems like I should just leave `oldxp` and `oldyp` alone, and switch to using dedicated variables that are never used in the physics of the game. So I'm introducing `lerpoldxp` and `lerpoldyp`, and replacing all instances of using `oldxp` and `oldyp` that my over-30-FPS patch added, with `lerpoldxp` and `lerpoldyp` instead. After doing this, and applying #503 as well, my Nova TAS syncs after some minor but acceptable fixes with Viridian's walkingframe. |
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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
- Created by Terry Cavanagh
- Room Names by Bennett Foddy
- Music by Magnus Pålsson
- Metal Soundtrack by FamilyJules
- 2.0 Update (C++ Port) by Simon Roth
- 2.2 Update (SDL2/PhysicsFS/Steamworks port) by Ethan Lee
- Beta Testing by Sam Kaplan and Pauli Kohberger
- Ending Picture by Pauli Kohberger
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).