> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getrivet.ca/llms.txt
> Use this file to discover all available pages before exploring further.
# Visual bilateral stimulation
> Stimulus shapes, motion paths, sizing, color, and the 0.3 to 2.0 Hz clinical range — every setting behind the moving stimulus.
The visual modality is the default and most familiar form of bilateral
stimulation. The set runs inside the session, with both of you in frame the
whole time — there's nothing for your client to install and nowhere else for
them to go.
The visual speed is hard-capped at **2.0 Hz**. The cap holds wherever the
speed can be set — the Configure modal, the stepper during a running set,
and any stored setting — and it can't be raised.
See [Photosensitive epilepsy safety](/emdr/photosensitive-epilepsy-safety).
## Stimulus shapes
Five shapes — nothing extra to download.
| Shape | Default for | Notes |
| ------------- | ------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| **Dot** | Classic mode | A solid filled circle. Maximum clinical familiarity — the Shapiro standard stimulus. |
| **Butterfly** | EMDR 2.0 mode | A symmetric two-wing silhouette. Recognizable to EMDR-trained therapists as the butterfly-hug-adjacent shape (Artigas & Jarero 2014). |
| **Flame** | — | A soft tapered shape with a candle-flame outline. Useful for clients who report the dot feels too clinical. |
| **Star** | — | A five-point star with sharper edges and more visual texture. |
| **Square** | — | A clean geometric for clients who prefer neutral and non-symbolic shapes. |
All shapes render at the same configured pixel size and color regardless of
which one you choose. The shape is a stylistic preference, not a clinical
parameter.
## Motion paths
Six paths control the trajectory of the stimulus across the canvas.
* **Horizontal** — left to right oscillation. The default and most clinically
familiar pattern. Matches the eye movement Shapiro's original protocol
used.
* **Vertical** — top to bottom oscillation. Useful for clients who report
visual fatigue on horizontal or who track vertical more comfortably.
* **Diagonal ↗** — bottom-left to top-right.
* **Diagonal ↘** — top-left to bottom-right.
* **Circular** — continuous circular orbit around the center of the canvas.
* **Figure 8** — figure-eight loop.
The diagonals, circular, and figure-8 paths are options for clients who
report habituation on a single axis. Clinical norm is horizontal; the
others are tools to keep in your back pocket.
## Speed
The rate slider runs from **0.3 Hz to 2.0 Hz**. The values you'll reach for
most often:
| Rate | Use case |
| ------------ | --------------------------------------------------------------------------- |
| 0.3 – 0.7 Hz | Initial Phase 2 testing; clients reporting visual overwhelm at higher rates |
| 1.0 Hz | Classic EMDR (Shapiro standard) baseline |
| 1.2 – 1.8 Hz | EMDR 2.0 working range (de Jongh / Matthijssen published range) |
| 1.5 Hz | EMDR 2.0 default |
| 2.0 Hz | Upper edge of clinical norm and the hard safety cap |
The 2.0 Hz cap is enforced because sustained visual flicker above \~3 Hz can
trigger photosensitive seizures in susceptible individuals (WCAG flicker
guideline). 2.0 Hz sits comfortably below that threshold and also stays
within EMDR clinical practice norms — every published EMDR and EMDR 2.0
protocol stays at or below 2 Hz.
## Size
The stim-size slider runs from **16 to 48 px**. Default is 32 px.
This is the size of the stimulus within the frame, not on any particular
screen. The frame scales to whatever your client is on, so a 32-px
butterfly reads the same relative size on a phone, a tablet, and a laptop.
Larger sizes (40–48 px) read well on phones; smaller sizes (16–24 px) suit
desktop screens at typical viewing distance.
## Color
The stimulus reads white against the backdrop, with a small indigo accent —
high contrast, and legible across screens and lighting conditions.
## Auto-vary
A toggle in the Configure modal. When on, speed, size, and brightness
each vary slightly over the course of a set — staying strictly inside
the clinical bounds. Auto-vary cannot push the speed above 2.0 Hz or
the size above 48 px.
Rationale: monotonous stimulation lets working memory habituate. Mild
variation keeps the dual-task engaging. Grounded in Engelhard / Littel
working-memory taxation research.
Default is **off** in both modes. Turn it on for sets where you want a less
predictable visual envelope.
## Changing the visual mid-set
Nudge the speed during a set and the movement picks up the new pace on the
next pass — no restart, no reload, no gap. The sound and any paired phone
land on the same pass, because they come from the same movement rather than
following it. See [One movement, not three](/emdr/staying-in-sync).
Shape, path and backdrop change from the Configure modal and take effect
when the next set starts, so a set never changes shape underneath your
client.
If the connection degrades mid-set, **stop the set yourself**. A set runs
its own timer regardless of what the connection is doing — Rivet won't stop
it for you, and stimulation your client is receiving while you can't see
them isn't stimulation you're running.
## Related articles
The audio modality — eight sound presets, L↔R panning, frequency, and
volume.
Eight gradient scenes and eight photo backdrops to settle the visual
field behind the stimulus.
The 2.0 Hz hard cap, the first-use warning modal, what to screen for.