Snapshots
Snapshots sound simple to implement, because one may think it is just keeping up a table and indexing the time.
INFO
In reality, it is a bit more complicated - but still very straightforward once you understand it.
You want to get an "interpolated snapshot" at the current renderTime rather than just the raw snapshot for that time.
Why Interpolation Matters
Imagine this scenario:
- You are sending CFrames at 30Hz, which is roughly 33.3ms per position update.
- A player is at 17ms between updates.
You now have:
- Snapshot at 0ms
- Snapshot at 33ms
If you simply snap to either snapshot, motion will look jittery or disconnected.
Key Concept
Interpolating between the two snapshots allows you to estimate the player’s state at 17ms smoothly.
Snapshot Interpolation Methods
There are two common methods for snapshot interpolation:
- Linear Interpolation
- Hermite Interpolation
1. Linear Interpolation
Linear interpolation is the simplest and most common method.
- You linearly interpolate between snapshots as you move forward through the array.
- This is the recommended approach for most snapshot systems.
2. Hermite Interpolation
Hermite interpolation is the method Roblox uses.
- It is calculus-based and approximates functions
- Hermite interpolation constructs a polynomial that matches both values and derivatives at specific points
- It produces smoother curves, especially for easing in and out of motion
Complexity
Hermite interpolation adds unnecessary complexity for most use cases.
It is not required for basic snapshot smoothing.
Additional Resources
Further Reading: Snapshot Interpolation – Gaffer on Games