Fulldive
Key points
- Full-dive is a state in which actions within an artificial world are established with bodily and sensory consistency.
- In VR that involves real-world body movement, the grounds for action and sensory consistency tend to “leak” into the real world, so it should be treated as distinct from full-dive.
- Full-dive is approached only when five elements are established simultaneously—motion suppression, sensation suppression, motor-intention acquisition, simulation, and sensory presentation—and Motion-Less VR is an engineering approach to tighten these conditions.
Introduction
Full-dive is not simply “VR with extremely beautiful visuals.”
Even though the physical body in the real world does not move, in an artificial world one’s body moves naturally, interacts with the environment, and the consequences return to the body as sensations. Moreover, the experience continues without interruption, with extremely little incongruity.
Only when these conditions are met do we consider it appropriate to call the experience full-dive.
Definition of Full-Dive
On this page, we define full-dive as follows.
[Definition of Full-Dive]A state in which actions within an artificial world are established in bodily and sensory consistency.
The key point here is “established within the artificial world.”
If the establishment of action depends on motion or sensation in the real world, then the artificial-world side can no longer control the conditions for establishment by itself. In that sense, full-dive can be organized as a state in which the basis for establishment is fully recovered on the artificial-world side.
Why VR That Involves Real-World Body Movement Is Unlikely to Be Full-Dive
Most common VR systems today, which involve actually moving the body, have the advantage of being intuitive and often immersive.
However, under the definition used on this page, it is difficult to call such systems full-dive. The reason is that “action” and “sensory consistency” do not easily remain self-contained within the artificial world.
Action “leaks” into the real world
If you swing your arm in the real world, the outcomes of motion—muscle contraction, joint rotation, inertia, and fatigue—are established in the real world first. Actions in the artificial world inevitably become something that follows that real-world establishment.
In other words, the “basis by which the action is established” does not stay inside the artificial world; it leaks into the real world.
Sensory consistency depends strongly on the real environment
Sensory inputs from the real environment—floor hardness, weight shift, gravity, and so on—tend to collide with the design of the artificial world.
Even if the artificial world presents “deep snow” or “the weight of a gigantic sword,” consistency collapses instantly if those sensations do not match what the physical body actually receives.
For these reasons, VR that involves real-world body movement tends to make the basis of action and consistency depend on the real world, so it should be treated as clearly distinct from full-dive.
The “Five Elements” Required to Establish Full-Dive
Full-dive is not determined by a particular “technical method,” but by its conditions for establishment.
On this page, the following five elements are treated as equally important. If even one is missing, the experience cannot be established.
(1) Suppression of motion
If the real body moves, the establishment of action leaks into the real world. Therefore, creating conditions under which real-world motion does not occur is a fundamental prerequisite.
(2) Suppression of sensation
The sense of restraint and pressure that arises when motion is suppressed can collide with feedback from the artificial world and break consistency. Thus, an approach that minimizes unnecessary sensory input is required.
(3) Acquisition of motor intention
If the body does not move, we cannot use real joint motion as input. We must extract the intention to move (rather than the result of movement) and use it to bring actions to life within the artificial world.
(4) Simulation
The extracted intention must be received and used to compute the physical behavior of the body and environment within the artificial world. This is not merely “visual animation,” but the core processing that establishes the causal relationship between action and outcome.
(5) Sensory presentation
The outcome of an established action must be returned to the body. Not only vision, but also kinesthetic sensation (e.g., through kinesthetic illusions) must be included, and feedback must be designed so that contradictions between sensory modalities are minimized.
[Insert Figure 1 here: A diagram placing the five elements on equal footing, with “Full-Dive Establishment” in the center.]
What Is Motion-Less VR?
Based on the conditions above, we define Motion-Less VR as follows.
[Definition of Motion-Less VR]Moving an avatar in an artificial world as if it were the real body, without physical movement, and having the results return as sensations.
This definition aligns well with the five elements of full-dive.
Because it involves no physical movement, suppression of motion and sensation becomes a prerequisite. Because intention is treated as input, acquisition of motor intention is required. Then simulation is performed within the artificial world, and results are returned through sensory presentation.
Exploring Motion-Less VR is also a process of engineeringly clarifying the conditions under which full-dive can be established.
[Insert Figure 2 here: A flow diagram of Motion-Less VR showing the five elements forming a closed loop.]
Why “Brain-Direct (BCI)” Is Not an Immediate Answer
In discussions of full-dive, approaches that “connect electrodes directly to the brain” (e.g., brain-machine interfaces) are often framed as the ultimate solution, because they appear to avoid moving the real body.
However, for general use, brain-direct approaches can make the conditions for establishment far more demanding rather than lowering the hurdle.
Limits of sensors and resolution
With non-invasive measurement (e.g., recordings from the scalp), the granularity of information tends to be coarse. With invasive implantation, medical risks become very large.
Moreover, non-invasive sensing often suffers from signal mixing because measurements pass through the skull and skin, making it difficult to read targeted activity with fine separation.
In contrast, invasive sensing sharply increases burdens beyond surgery itself: infection risk, long-term stability, replacement issues, and ethical and institutional hurdles.
In addition, both approaches are sensitive to changes in wearing/placement conditions and electrode states, which can degrade reproducibility and make stable day-to-day operation difficult.
As a result, achieving resolution sufficient to read subtle fingertip force control and smooth continuous movements is extremely challenging.
Accuracy and stability
In full-dive, input errors directly appear as “mismatches between intention and outcome (incongruity),” which can destabilize the experience.
Keeping the system stably operational under everyday individual differences and physical/mental condition fluctuations is a high hurdle.
Safety and operating cost
Along with fail-safe requirements in case of malfunction and security risks, the daily operational burden of wearing the system and performing calibration becomes a major barrier to widespread adoption.
Brain-direct approaches can look like a shortcut to full-dive, but the conditions for real-world deployment are extremely heavy.
A reasonable inference
As a reasonable inference, if brain-direct approaches were to become practical for general use, the conditions required for Motion-Less VR would already have been satisfied beforehand.
Even if brain signals could be read perfectly, full-dive would still fail unless a high-quality closed loop—intention → simulation → sensory return—were established.
Common Misconceptions
- “Brain-direct is the only answer.”
This is often said, but it is usually clearer to treat full-dive as a set of establishment conditions, not a single technology.
- “If visuals are high-fidelity, it becomes full-dive.”
This is also said, but full-dive approaches establishment only when not only vision, but also action and sensory return are consistent.
- “Full-dive is the evolved form of full-body tracking.”
This viewpoint exists, but methods in which the real body moves are structurally different from full-dive under the definition used on this page.
FAQ
Q1. Can full-dive like in anime or SF be realized?
It is certainly possible to discuss its feasibility. However, it is not a magical technology that suddenly becomes complete one day. Only when the five elements—suppression of motion, suppression of sensation, acquisition of motor intention, simulation, and sensory presentation—are established simultaneously can we approach that state.
Q2. Why can’t VR that involves moving the body be called full-dive?
Because the establishment of action and sensation “leaks” into the real world. Once real-world body motion is established first, physical sensory inputs from the real environment (gravity, floor contact, etc.) tend to collide with the design of the artificial world, making contradictions difficult to prevent.
Q3. What is Motion-Less VR?
It is a system in which, without physical body movement, you move an avatar in an artificial world as if it were your own body, and the results of that action return to you as appropriate sensations (including kinesthetic sensation).
Q4. If brain-direct technology becomes possible, wouldn’t full-dive be complete?
No. Brain-direct is only one possible “input/output interface (an entrance and exit).” Safety and accuracy challenges are extremely large. Moreover, unless the “simulation and feedback loop” that correctly processes intentions within the artificial world and returns sensations without incongruity is complete, the experience will not be established.
Q5. Why is “kinesthetic sensation” important, not just vision?
Human action requires “return” (a sense of response). If you try to make someone feel as if they moved using vision alone, contradictions with real bodily sensations can arise and the experience collapses. Reducing cross-modal contradictions through force/ tactile cues and kinesthetic illusions is directly tied to establishing full-dive.
Conclusion
Full-dive is a set of establishment conditions, and Motion-Less VR is a practical approach for constructing an artificial world in the direction of satisfying those five elements simultaneously.
At our laboratory (Artificial World Implementation Laboratory: AWIL), we are advancing research toward realizing Motion-Less VR.
In particular, we are working on system integration of element technologies that constitute Motion-Less VR, such as acquiring motor intention through devices that detect “attempted force to move” (e.g., lower-limb joint torque) while the body is fixed, and sensory presentation via kinesthetic illusions using tendon vibration and skin-traction stimuli.
Rather than waiting for distant-future brain-direct technology, we will open up new forms of interfaces in which action and sensation are completed within the artificial world, starting from present-day engineering approaches.
Noriki Mochizuki