Inside SCYTHE: How a Custom, Data‑Driven HUD Turns Unity Into a Scientific Instrument

https://1drv.ms/u/c/2d2d70fa95d61901/IQBDcX4CvFOpS7WCUBInWJliAXXrrdtlE9IOY-AJ0D3WgSg?e=agfOjv (31MB Windows executable Unity App)

We seek to create the SCYTHE_AR user experience within Unity. Most Unity heads-up displays are decorative.
They’re layered UI canvases, animated sprites, and shader flourishes designed to look good.

SCYTHE’s HUD is none of that.

It’s a scientific interface built on top of a deterministic RF laboratory. Every pixel, every indicator, every overlay is driven by real data flowing through a reproducible simulation pipeline. The HUD isn’t a skin on top of the system—it is the system’s window into the world.

This post walks through how SCYTHE’s HUD works, why it’s architected this way, and what makes it fundamentally different from traditional Unity UI.

A HUD Built on Determinism, Not Decoration

SCYTHE’s simulation core is deterministic:

Fixed‑step simulation clock
Seeded AWGN
Free‑space attenuation
ASK/FSK/BPSK/QPSK modulation
Reproducible TX→IQ→channel→RX pipeline
Spatial RF sampling
One‑way Doppler from operator motion

The HUD doesn’t invent values.
It doesn’t smooth them.
It doesn’t “fake” signal strength or noise.

It reads directly from the RF pipeline every frame.

This makes the HUD a measurement instrument, not a UI layer.

Every Element Is Data‑Driven

Signal Bars

The five‑bar indicator is computed from:

instantaneous received power
SNR
distance
modulation type
channel noise floor

Bars rise and fall based on real RF conditions, not arbitrary thresholds.

Bearing Arrow

The arrow pointing toward the transmitter uses:

world‑space TX position
operator position
operator forward vector
normalized bearing angle

It’s a true directional indicator, not a sprite that rotates for show.

Range Rings

Range rings are rendered using:

inverse‑square attenuation
scenario‑defined TX power
deterministic spatial sampling

They visualize actual RF reach, not a guessed radius.

Doppler Readout

Doppler is derived from:

operator velocity
radial component toward TX
carrier frequency

It’s a one‑way Doppler model, explicitly labeled as such.

Power‑Density Map

The 2D RF field overlay is:

approximate
evidence‑labeled
derived from free‑space loss
updated at arbitrary world positions

It’s intentionally honest about what it represents.

TX and Operator Markers

These markers are not UI icons—they’re spatial anchors tied to:

scenario manifest
character controller
transmitter transform

The HUD reflects the world, not the other way around.

A Custom Pipeline, Not Unity UI

SCYTHE’s HUD bypasses Unity’s typical UI stack.
Instead, it uses:

custom C# data bindings
deterministic sampling
lightweight rendering
built‑in pipeline compatibility
no external dependencies
no URP/HDRP
no smoothing or interpolation

This keeps the HUD:

fast
predictable
reproducible
platform‑consistent

And because it’s custom, it integrates seamlessly with the RF and optics subsystems.

Why This Matters

A scientific simulator must be honest.

If the HUD invents values, smooths noise, or hides uncertainty, the operator sees a story, not a measurement. SCYTHE rejects that approach. The HUD is a direct expression of the underlying physics model—no more, no less.

This makes SCYTHE suitable for:

RF education
algorithm prototyping
scenario testing
optics dataset visualization
AR monocle research
reproducible experiments

It’s not a game HUD.
It’s a field instrument.

What Comes Next

As SCYTHE evolves, the HUD will expand to include:

multi‑transmitter overlays
occlusion‑aware attenuation
optical depth‑plane visualization
fused RF + optical monocle overlays
scenario‑driven RF events
uncertainty cones
multipath approximations (explicitly labeled)

But the principle remains the same:

The HUD must always show the truth of the simulation, not a stylized interpretation.

That’s the core of SCYTHE’s design philosophy—and the reason its HUD feels more like a scientific device than a Unity UI.