Testing the Accuracy of ROBLOX Physics with Potato Cannons

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Potato Cannon ScreenshotROBLOX is built on a comprehensive physics engine, and our developers are constantly optimizing it so it can handle interactions between more physics objects and players, in an increasingly accurate and consistent way. We recently put our engine to the test with a new projectile-motion simulator – and most satisfying armament – the ROBLOX Potato Cannon. According to the results, which we describe in this article, we’re on the right trajectory.

The ROBLOX Potato Cannon mimics its real-world counterpart, a contraption traditionally constructed using a pipe and some means of generating air pressure. The difference is our potato cannon automatically performs the calculations you need to hit your target. We constructed the potato cannon so it computes the launch angle and, with the velocity at a constant 300 studs/second, the correct trajectory for your now-deadly potato. If your target is outside its range, it defaults to the maximum distance it can shoot.

Let’s look at how we calculate a potato’s trajectory for maximum distance and how the ROBLOX Potato Cannon stacks up against real-world physics.

Potato Cannons: ROBLOX Vs. Real World

In ROBLOX, one real-world meter is 20 studs. We can use that conversion to determine ROBLOX’s acceleration due to gravity. In the real world, acceleration due to gravity is 9.81 meters / second^2. When we multiply that number by 20 studs, we arrive at the acceleration due to gravity in ROBLOX: 196.2 studs / second^2.

With the muzzle velocity of our Potato Cannon at 300 studs/second, we can determine the Maximum Distance, Maximum Height and Time Traveled (twice the time it takes to reach the maximum height, assuming there is no air resistance) for the projectile.

Maximum Distance Equation

Maximum Height Equation

Time Traveled Equation

θ (Theta) is the launch angle of the projectile. The projectile will reach peak distance when θ = 45° – see the Wikipedia article on projectile motion for more information.

When we plug in our values for velocity (300 studs/second), launch angle (45°) and acceleration due to gravity (196.2 studs / second^2), we can compute the Maximum Distance, Maximum Height and Time Traveled as:

Maximum Distance Calculation

Maximum Height Calculation

Time Traveled Calculation

We can compare these calculations to the in-game performance of the ROBLOX Potato Cannon. Our results show that its trajectory is almost exactly what we calculated in the above formulas.

Potato Cannon Trajectory Test Output

You can see that the distance, height and time traveled, as simulated by ROBLOX’s physics engine, are very close to the real-world values. We suspect the marginal error in Maximum Distance is probably due to the “touch” events not polling fast enough and the discrepancy in Maximum Height is due to the Lua-side polling performed by the script.

Sure, the ROBLOX Potato Cannon is an intimidating piece of virtual gear you can tote around with your character. But it’s also a physics lesson in disguise — one that verifies the accuracy of ROBLOX’s engine.

147 thoughts on “Testing the Accuracy of ROBLOX Physics with Potato Cannons”

  1. I thought this was funny because potato cannons were the most obvious for physics.

  3. Strange that 300 studs is 1 meter because I thought 1 stud was half of the leg of the roblxians…

    • No, one real world meter is 20 studs. The potato’s initial launch speed is 300sps (Studs Per Second) which would equal roughly 15mps (Meters Per second) in the real world. Pay attention and learn to read. XD JK

      • I actually been needing some conversion between Real World Speed/Distance and ROBLOX Speed/Distance. TY ROBLOX. But I still need how the speed of cars is measured. When you config the speed of a car are you configuring it’s max speed in SPS or Roblox Meters Per Second?

  7. It doesn’t seem right for it to be 20 studs equaling a meter. That means with how many studs tall the player is (5), the characters are less than a foot tall!

  8. l pm’d Sorcus saying ‘Your A Troll’ He replied; “Yeah l guess, have a couple hundered k for ya trouble
    Sorcus”
    That’s how l got rich! -True-

  9. Wait, if 20 studs is like a real life meter…and that characters usualy walk at 16 studs per seconds…it means they’re super slow!

  10. OVERPOWERED for just an potato, it shoots very long distance and is like a sniper, also its one hit KO

  14. lol,what if you changed 20 studs=1 meter to 30 studs=1 meter,I’m pretty shure that would make it so you would have to change everything like…gravity:9.83/seccond^3 then im pretty shure you would change all that and it would look totaly different!

  15. Guys, you do realize that if 20 studs is a meter than each robloxian is 9 1/4 inches tall.

  16. impressive math…….i wish i could understand it XD

    • See the quantrum of the math is 20 right?20=300 so that means the average raidus diameter simplephone would be 9.134 Right? Correct me if im wrong but then the potato cannon would fly at a speed that would kill an eleplant since the trajectory rate to kill a man is 5.465 rounded to 5 then making an average joe guesstimate the trajectory would be 9.14 easy! And thats how to kill the eleplant! But anyways to complete the math youd have to understand Calculus,most importantly Aernestz theory. Therefore its 20=9.14!=To ig3 Understand? Nah Im just messing with you this is to hard :|

  17. roblox should make the water more realistic by having it splash, instead of making a hole when it is exploded

  19. This means the studs are meters, or at the ratio of a meter.
    If it’s just a meter, we take LARGE steps.

    • No… studs are nothing like metres and gravity on Earth is nowhere near 192 metres/second.

  30. They need to be combustible lemon cannons.

    AND I’M A POTATO!

  32. I think that is amazing how you can make a potato cannon in the virtual world, and a potato cannon in the physical world; and sync them almost exactly! Good job :D