The unified spatial and temporal reference frame that separates high-fidelity systems from surface-level approximations.
The synthesis criterion for the Foundation layer. A system that meets all five of the following criteria operates in true 3D space; failure to meet even one disqualifies it from that classification.
Operating in true 3D space means that a simulator's physics, motion, and visual systems all exist within the same unified spatial and temporal reference frame.
In this state, every element of the simulation behaves according to the same physical laws, the same origin of motion, and the same time synchronization, exactly as they do in the real world.
This is not a visual illusion or a mechanical approximation. It is a physically valid recreation of real-world motion, where the simulator exists inside the environment, not in front of it.
Many systems claim "3D motion" because they move through three axes. However, true 3D space operation requires that these movements originate from correct physics, operate around the true center of mass, and maintain synchronization with the visual environment. Mechanical displacement through space alone does not qualify.
A simulation system must meet all five of these criteria to operate in true 3D space. Failure to meet even one disqualifies the system from true 3D classification.
All motion must originate from rigid-body dynamics that accurately represent real-world vehicle behavior. Inputs such as torque, mass, inertia, and velocity produce outputs of true translational and rotational motion, not preprogrammed effects or amplified forces.
This ensures that every movement is a physical consequence, not a visual reaction.
Each axis of motion (yaw, pitch, roll, surge, sway, heave) must be mechanically isolated and independently controllable. True 3D operation depends on orthogonal motion vectors: movement along one axis must not cause motion along another.
This eliminates cross-axis interference and preserves true rigid-body kinematics.
All rotations and translations must occur around the true center of mass of the simulated vehicle or aircraft. If the pivot or rotational origin is displaced, as in Stewart platforms or 4-post systems, spatial distortion occurs.
The center of mass is the only physically correct origin for 3D motion.
The visual environment and the motion platform must share a single physical reference frame. The operator must exist within the visual world, not in front of it.
If visuals and motion are disconnected, the experience collapses from 3D to 2D, because the brain no longer perceives synchronized spatial depth or presence.
Physics, motion, and visuals must operate in a real-time, closed-loop system meeting a low-latency requirement. This ensures alignment between vestibular, proprioceptive, and visual cues.
Even minor timing discrepancies produce sensory conflict, which the human brain detects immediately.
Definition: Simulation must be governed by real-time vehicle physics rather than post-processed motion effects or approximations.
Failure Consequence: If physics is not the source of motion, the system cannot reproduce correct vehicle behavior.
Full treatment: Physics First
Definition: Rotational and translational axes must operate independently rather than through mechanically coupled substitutes.
Failure Consequence: If axes are coupled, the system cannot deliver clean motion cues or valid rotational behavior.
Full treatment: Independent Degrees of Freedom
Definition: Motion must resolve relative to the vehicle's center of mass rather than an arbitrary platform or seat reference.
Failure Consequence: If motion is not resolved at the center of mass, the driver receives incorrect information about trajectory and state.
Full treatment: Rigid Body Dynamics
Definition: The participant must experience motion and visual change as a single coherent environment rather than as disconnected layers.
Failure Consequence: If the visual and motion frames are not unified, perception becomes compromised and timing degrades.
Full treatment: Yaw in Simulation
Definition: Physics, motion, and visuals must operate in a real-time, closed-loop system meeting a low-latency requirement.
Human sensory systems detect timing discrepancies at the millisecond level. Physics calculations, motion output, and visual rendering must all remain within a sub-threshold latency window.
This real-time synchronization ensures:
Failure Consequence: Even minor timing discrepancies produce sensory conflict that the brain detects immediately. Delayed motion relative to visual input breaks spatial coherence and degrades fidelity.
No dedicated upstream page exists for temporal synchronization. This criterion is fully treated on this page.
Any system that fails one or more of the five core criteria does not operate in true 3D space, regardless of how many axes it moves through or how expensive the hardware is.
| System Type | Failure Mode | Classification |
|---|---|---|
| Hexapod Platforms | Coupled actuator geometry; incorrect center of rotation; visual-motion separation | Fail: 2D / Surface-Level |
| 4-Post Motion Systems | Force-based motion blending; external visual alignment | Fail: 2D / Surface-Level |
| Static or Non-Motion Rigs | No vestibular engagement or physical dynamics | Fail: 2D Representation |
| True 3D Systems | Independent DOF; correct center of mass; unified visual-motion frame; physics-first; synchronized | Pass: True 3D Space |
These surface-level systems may appear to move in 3D, but because they do not adhere to rigid-body physics or unified reference frames, their operation is geometrically blended, perceptually inconsistent, and physically invalid.
3D space in simulation is not defined by how many axes a system moves through. It is defined by how accurately those motions correspond to:
A simulator that meets all five core criteria operates in true 3D space: physics, motion, and visuals inseparably unified in a single reference frame.
Any system that fails to meet even one criterion remains a surface-level approximation, not an in-the-loop recreation of real-world motion.
The Definition criterion completes the Foundation layer. From here the framework moves into the Control Layer, beginning with the architectural conditions a system must satisfy before measurement can proceed.