Bug Tracking for Physics Sandbox Games

Physics sandbox games hand players a physics playground and the freedom to build, combine, and experiment however they like, with no goal but to play with the physics. This total freedom, combined with a physics simulation, produces emergent physics bugs at the extremes: a construction that becomes unstable and explodes, a configuration that breaks the simulation, a scale of objects or constraints that overwhelms the physics, all created by players pushing the sandbox in ways no designer anticipated. Like other sandbox and physics genres combined, these depend on the construction and the physics state. Tracking physics sandbox bugs means capturing the construction, physics, and scale behind a player-created experiment.

Free physics play produces emergent bugs

A physics sandbox game gives players a physics simulation and total freedom to build, connect, and experiment, dropping objects, building structures, connecting things with constraints and joints, and watching the physics play out, with the whole point being free experimentation with the physics. This combination of a physics simulation and total player freedom produces emergent bugs, since players build and combine in ways no designer anticipated, pushing the physics into configurations and scales that expose its limits.

The bugs are emergent physics failures: a construction that becomes unstable and shakes itself apart, a configuration of constraints that the physics solver cannot handle, a scale of objects that overwhelms the simulation, a combination that produces non-finite values and breaks the physics, like the physics bugs of any physics game but driven by unconstrained player creativity, as in sandbox games. Understanding that free physics play produces emergent physics bugs, at the extremes players push the sandbox to, frames the bug tracking: capture the construction, the physics state, and the scale behind a physics experiment that broke, since the bugs come from player-created configurations you did not anticipate.

Capture the construction and object state

The core context for a physics sandbox bug is the construction and object state, what the player built, the objects, their configuration, the constraints and joints connecting them, since an emergent physics bug arises from a specific construction the player created, and reproducing it requires that construction, like capturing the world state in a sandbox game. Capture the construction, the relevant objects and their connections, when a bug is reported.

Capture enough of the construction to recreate it, the objects, their positions and properties, the constraints and joints, since the emergent physics bug depends on the specific configuration the player built. With the construction captured, you can recreate the player creation and watch the physics bug happen, which is the only reliable way to reproduce an emergent bug from a configuration you did not design. The construction and object state is the player creation from which the physics bug emerged, and capturing it is what lets you recreate the experiment that broke the physics. Capturing the construction and object state is the foundation, providing the player-built configuration behind an emergent physics sandbox bug.

Capture the physics state

Because physics sandbox bugs are physics bugs, capture the physics state, the positions, velocities, forces, and the state of the constraints and joints, since the physics situation is what determines and reveals the bug, much as in any physics game. Capture the physics state of the relevant objects when a bug is reported, so you can see the physics situation that produced the instability or failure.

A report of a construction exploding, shaking apart, or behaving impossibly becomes diagnosable when you can see the physics state, the velocities and forces, the constraint states, revealing whether the physics went unstable, the constraints conflicted, or the solver diverged. The physics state, especially around instability, the velocities spiking, the forces growing, the constraints fighting, shows the physics failure in action. Capturing the physics state, alongside the construction, gives you both the player creation and the physics situation it produced, which together let you reproduce and understand the emergent physics failure, since the physics state shows what the construction did to the simulation.

Watch the scale and instability

Physics sandbox bugs often appear at scale, since players build large constructions, connect many objects with many constraints, and create configurations that push the physics to its limits, and the simulation can be overwhelmed by the scale, the object count, the constraint count, producing instability or failure. Capture the scale, the object and constraint counts, when a bug is reported, since a bug at high scale is reproducible only if you know the scale, and many physics sandbox bugs are scale-dependent.

Watch instability especially, the characteristic physics sandbox bug, where a construction or configuration becomes unstable, the physics shaking it apart, the constraints fighting, the values diverging, often at scale or in extreme configurations, like the physics instability of any physics game but driven to extremes by player creativity. Capture the instability context, the construction and physics state as it destabilized. Watching the scale and instability, capturing the object and constraint counts and the instability state, covers the extremes where physics sandbox bugs concentrate, since the free play drives the physics to scales and configurations where the simulation destabilizes, which is exactly where the genre emergent physics bugs live.

Setting it up with Bugnet

Add an in-game report option and attach the construction and object state, the physics state, and the scale, the object and constraint counts, as a serialized blob and custom fields. Bugnet stores them so a physics sandbox bug arrives with the construction, physics, and scale context needed to recreate the player creation and reproduce an emergent physics failure at the scale and configuration it occurred.

Enable automatic crash capture for the physics failures that produce non-finite values and crash, and group identical issues into occurrence counts, watching whether bugs cluster at scales or configurations. Because physics sandbox games produce emergent physics bugs from free player creativity at extreme scales, the captured construction-and-scale context is what lets you recreate the player experiment and reproduce the physics failure, finding whether it is an instability, a constraint issue, or a scale limit, keeping the physics playground robust to the creative, extreme configurations players build, which is exactly where the genre invites them to push and where its bugs emerge.

Harden the physics against extremes

Since physics sandbox players push the physics to extremes you cannot fully anticipate, the goal is to harden the physics against the extremes, making the simulation robust to large scales, complex constraint configurations, and the instabilities players create, so the physics degrades gracefully or stays stable rather than exploding or crashing. Your captured bugs, showing the constructions and scales that break the physics, tell you where to harden, the configurations and scales the simulation cannot handle.

This hardening, capping or stabilizing the physics under extreme configurations, handling the scale, preventing the non-finite values that crash, is the response to the emergent physics bugs, much like making any sandbox engine robust to player creations. Combine the hardening, guided by the captured bugs, with the understanding that some physics chaos is the fun, distinguishing the instabilities that are entertaining from the ones that crash or break the game. Hardening the physics against the extremes players create, using the captured construction-and-scale bugs to find where the simulation fails, is how you keep a physics sandbox robust to the creative, extreme play it invites, so the playground withstands the experiments players bring to it without crashing.

Physics sandboxes invite players to push the physics to its limits. Capture the construction and scale, and harden against the extremes.