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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| src | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CONTRIBUTORS.txt | ||
| README.md | ||
How to Build
VVVVVV's official desktop versions are built with the following environments:
- Windows: Visual Studio 2010
- macOS: Xcode CLT, currently targeting 10.9 SDK
- GNU/Linux: CentOS 7
The engine depends solely on SDL2 and SDL2_mixer. All other dependencies are statically linked into the engine. The development libraries for Windows can be downloaded from their respective websites, Linux developers can find the dev libraries from their respective repositories, and macOS developers should compile and install from source (including libogg/libvorbis/libvorbisfile).
Steamworks support is included and the DLL is loaded dynamically, you do not need the SDK headers and there is no special Steam or non-Steam version. The current implementation has been tested with Steamworks SDK v1.46.
To generate the projects on Windows:
# Put your SDL2/SDL2_mixer folders somewhere nice!
mkdir flibitBuild
cd flibitBuild
cmake -G "Visual Studio 10 2010" .. -DSDL2_INCLUDE_DIRS="C:\SDL2-2.0.10\include;C:\SDL2_mixer-2.0.4\include" -DSDL2_LIBRARIES="C:\SDL2-2.0.10\lib\x86\SDL2;C:\SDL2-2.0.10\lib\x86\SDL2main;C:\SDL2_mixer-2.0.4\lib\x86\SDL2_mixer"
Note that on some systems, the SDL2_LIBRARIES list on Windows may need
SDL2/SDL2main/SDL2_mixer to have .lib at the end of them. The reason for this
inconsistency is unknown.
To generate everywhere else:
mkdir flibitBuild
cd flibitBuild
cmake ..
macOS may be fussy about the SDK version. How to fix this is up to the whims of however Apple wants to make CMAKE_OSX_SYSROOT annoying to configure and retain each time Xcode updates.
Including data.zip
You'll need the data.zip file from VVVVVV to actually run the game! It's available to download separately for free in the Make and Play edition of the game. Put this file next to your executable and the game should run.
This is intended for personal use only - our license doesn't allow you to actually distribute this data.zip file with your own forks without getting permission from us first. See LICENSE.md for more details. (If you've got a project in mind that requires distributing this file, get in touch!)
A Word About Compiler Quirks
(Note: This section only applies to version 2.2 of the source code, which is the initial commit of this repository. Since then, much hard work has been put in to fix many undefined behaviors. If you're compiling the latest version of the source code, ignore this section.)
This engine is super fussy about optimization levels and runtime checks. In particular, the Windows version absolutely positively must be compiled in Debug mode, with /RTC enabled. If you build in Release mode, or have /RTC disabled, the game behaves dramatically different in ways that were never fully documented (bizarre softlocks, out-of-bounds issues that don't show up in tools like Valgrind, stuff like that). There are lots of things about this old code that could be cleaned up, polished, rewritten, and so on, but this is the one that will probably bite you the hardest when setting up your own build, regardless of platform.
We hope you'll enjoy messing with the source anyway!
Love, flibit