Day 1 Spatial XR: The XR Spectrum — AR, VR, MR & Spatial Computing
Walking into Spatial XR as a complete stranger. No headset experience, no Unity projects, nothing. Starting from zero — here's everything I learned on Day 1.
The Mental Model That Frames Everything
In 1994, Paul Milgram and Fumio Kishino proposed something simple but powerful: reality and virtuality aren't two separate things. They exist on a spectrum.
|----------|--------------|--------------|----------|
Real Augmented Augmented Virtual
Environment Reality (AR) Virtuality Environment
(AV)
|<------------- Mixed Reality (MR) ------------->|
Left end — pure real world. No digital overlay. Right end — pure virtual environment. Everything computer-generated. Everything in between — some blend of real and virtual.
This is called the Reality-Virtuality Continuum, and every XR product sits somewhere on it.
The Four Zones
Augmented Reality (AR) — Real world is dominant, digital content layered on top. Pokemon Go, Google Maps Live View, Instagram filters. You still see reality — digital stuff is added to it.
Augmented Virtuality (AV) — Less talked about. The virtual world is dominant, but real elements are pulled in. A VR meeting room with live 3D scans of real participants.
Mixed Reality (MR) — The entire middle zone. In modern marketing (especially Microsoft and Meta), narrowed to mean experiences where digital objects interact convincingly with the real world — like a virtual ball bouncing off your real table.
Virtual Reality (VR) — Fully synthetic. Everything you see and interact with is computer-generated.
Why This Matters
Every product maps to this continuum. Apple Vision Pro's Digital Crown literally lets you dial between AR and VR — the most direct physical implementation of Milgram's model in any product. Apple calls it "Spatial Computing" to position the device as spanning the full continuum rather than being locked to one end.
The Core Tech: SLAM, 6DOF, Passthrough
Three technologies make spatial experiences possible. Every XR device depends on some combination of these.
SLAM — Simultaneous Localization and Mapping
The single most important technology in XR. The device answers two questions at once:
- Where am I? (localization)
- What does the space around me look like? (mapping)
Cameras and sensors capture the environment, identify visual features (corners of tables, edges of walls), track how those features move frame-to-frame to calculate the device's own movement, and build a 3D map in real time.
Without SLAM, a virtual object can't "stay" on your table. Your phone does this every time it places an AR object on the floor.
6DOF — Six Degrees of Freedom
How many ways a device tracks your movement:
- 3 Rotational: Pitch (nod up/down), Yaw (turn left/right), Roll (tilt sideways)
- 3 Translational: Left/right, Up/down, Forward/backward
The older 3DOF (rotation only) feels like sitting in a swivel chair. 6DOF (rotation + position) feels like actually being in the space. It's the minimum bar for convincing XR today.
Passthrough
The bridge between VR hardware and AR experiences. VR headsets have opaque displays — you can't see the real world. Passthrough uses outward-facing cameras to capture reality and display it on the internal screens, with digital content composited on top.
Apple Vision Pro's passthrough is so good it's the default mode — you see the real world unless you choose to go fully virtual. This is a key reason Apple positions it as a spatial computer, not a VR headset.
The Big Three: Meta, Apple, Google
Three companies, three completely different strategies.
Meta — The Volume Play
Sell headsets cheap, get them everywhere. Quest 3 at $499, Quest 3S at $299 — sold at or near cost. Over $50 billion invested in Reality Labs since 2020. The bet: XR follows the smartphone adoption curve. Whoever owns the affordable hardware platform wins.
Position on continuum: VR-first, expanding toward MR through passthrough.
Apple — The Premium Experience Play
~10 years of R&D before shipping anything. Vision Pro at $3,499. No controllers — eye tracking and hand pinch gestures only. The bet: XR replaces the personal screen, not reality. People will use it for productivity and entertainment, not escaping into virtual worlds.
Position on continuum: AR-first, slides toward VR via the Digital Crown.
Google — The Platform & AI Play
Don't build the dominant headset — build the dominant platform. ARCore for phone-based AR. Android XR (with Samsung and Qualcomm) as the OS for headsets and glasses. The bet: same thing that won mobile wins XR — the operating system. Android powers ~72% of smartphones. If Android XR becomes the default OS for non-Apple headsets, Google controls the platform layer.
Position on continuum: Spread across it. The play is the software platform, not a fixed point.
Honest Assessment
Wins: The Milgram continuum immediately clarified every confusing product announcement I've seen. "Is Vision Pro AR or VR?" is the wrong question — it sits on a spectrum, and Apple literally built a dial for it.
Struggles: The hardware landscape is overwhelming. Dozens of companies, discontinued products, overlapping terms. Focusing on the three major strategies helped cut through the noise.
Key Insight: The technology (SLAM, 6DOF, passthrough) is converging. What differentiates the big three isn't the tech — it's the philosophy. Meta thinks XR is social. Apple thinks it's personal. Google thinks it's a platform. They could all be right about different use cases.
Tomorrow's Focus: Dive into development environments — Unity vs Unreal vs WebXR — and what it actually takes to build something for these platforms.
Day 1 of Spatial XR. The spectrum makes sense. Now to see what building on it feels like.
Follow along: @KarthNode