8/1 Hotfixes

It's been awhile! This update was supposed to be behind-the-scenes changes... but there were some bugs to fix. So, let's get into those!

Bugfixes

• Added "Backstop Bridge" to Survival Mode.

• Fixed the missing treads and tank collision splash visuals in Treasure Mode's "Backstop Bridge" map.

• Fixed controllers not working on the Target Practice menu after finishing a level.

• Fixed a scenario where the background music would not start on the Survival Mode and Target Practice menus.

• "Stability improvements"

What "Stability Improvements" Actually Means

If you've played Sumo Tanks a lot, you've probably noticed it occasionally crashes. For that, I am sorry.

Thanks to an investigation by a new developer and a bug report, I believe I have identified and fixed the root cause. In other words: no more Sumo Tanks crashes. I think the technical details are interesting, so I wanted to dive into them:

Internally, all the treads, tank collision splashes, and other colors shown on the mat of arenas are referred to as "the treads texture". In Sumo Tanks'first demo, the treads texture was updated pixel-by-pixel on the CPU whenever a shell moved or two tanks collided. If you had a big collision between multiple tanks, there was a cool slowdown effect... because the whole game froze as the CPU struggled to update the texture. To fix this, updating the treads texture was changed to use a "computer shader", which is essentially a program that runs on the GPU. CPUs are faster than GPUs when it comes to executing instructions one-by-one, but GPUs are much faster when they can execute instructions simultaneously. In Sumo Tanks' case, the computer shader updates every pixel of the treads texture simultaneously. This fixed the freeze and is the technique used in your version of Sumo Tanks today. However, it requires lower-level integration with the graphics card drivers, and this is where the crash was introduced.

The crash was caused by an interaction between two parts of the treads texture process: (1) compute shader resources are deleted when a level ends and (2) the compute shader is run separately from the level. If a level ended while the compute shader was still running, the shader could try and fail to access the deleted resources. That is what crashed Sumo Tanks. The compute shader still exists in this new version of Sumo Tanks, but its resources are no longer deleted until the shader has finished. As far as my testing shows, this fixes the crash.

This should improve the stability of Sumo Tanks. I am very sorry to any players who had a run cut short by this. If you ever encounter a bug or crash, please don't hesitate to reach out in the Steam Discussions. Thank you to the player that did.

Preventing Bugs in the Future

At the start of this post, I alluded to some "behind-the-scenes" changes. Fittingly to the "bug fix" theme of this update, those changes will help catch bugs in the future.

In software development, there is a thing called "regression testing", which is a fancy way to say "testing that nothing broke". For Sumo Tanks, this was a manual process that involved playing all levels and every arena on every game mode, both with and without controllers, both online and offline, both in the demo and full version of Sumo Tanks, and all with varying numbers of players. This "manual regression testing" took hours and, despite everything, it failed to catch the issue that led to the emergency "Hotfix for Treasure Mode" update last year.

A broken game mode is unacceptable, so the testing process itself had to be fixed. Thanks to the hard work of a new developer, Sumo Tanks now has "automated regression testing". With a press of a button and a few minutes, every level and arena can be verified. This automated testing does not cover everything, but it goes a long way to guaranteeing that all existing modes continue to work after an update. This saves hours of time, which allows for faster development and more testing where it is most needed. My hope is that this will help Sumo Tanks continue to be maintained and improved as time marches on.

...I think these patch notes ended up longer than the patch itself. If you made it to the end of this, thank you for reading. Regardless, thank you for playing Sumo Tanks!

— Hunt, Mountain Peke Games