> For the complete documentation index, see [llms.txt](https://yall.yassrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yall.yassrobotics.com/documentation/tuning/retroreflective-pipeline-tuning.md).

# Tuning a Retroreflective Pipeline

A retroreflective pipeline finds targets in two sequential stages: an HSV color threshold turns the image into a binary mask, then contour filtering/sorting picks which blob(s) in that mask are the real target. Tune them in that order — filtering a noisy mask is much harder than filtering a clean one.

{% hint style="info" %}
Do the [camera sensor settings](/documentation/tuning/camera-sensor-settings.md) pass first. A properly dark, low-exposure image makes the threshold step below almost trivial.
{% endhint %}

## Stage 1 — HSV color threshold

Switch the web UI's video feed to **threshold** view so you can see the binary mask update live while you tune.

| Slider         | What it does                                                                                                                 |
| -------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| **Hue**        | The "pure" color, independent of brightness (0 = red, \~59 = green). Tune this first — it's the most discriminating channel. |
| **Saturation** | Color purity — how washed-out (low) vs. pure (high) the color is.                                                            |
| **Value**      | Brightness — how much black is mixed in.                                                                                     |

Workflow:

1. Use the **eyedropper** tool on the target in the raw camera feed to center the HSV range on it automatically.
2. Refine with the **add**/**subtract** wands rather than dragging sliders blindly.
3. **Raise the minimum Value off of zero.** Leaving it at `0` passes black pixels through the mask, which is almost never what you want.
4. Keep every range **as small as possible** — the tighter the range, the more portable the pipeline is to other fields/lighting rigs.
5. If tracking a red target, enable hue inversion (red wraps around both ends of the hue range).

## Stage 2 — Contour filtering and sorting

Once the mask is clean, filter which contours in it count as "the target," in this order:

1. **Target Area** — eliminates obviously-wrong-size blobs first (stadium lights, scoreboard displays). The area slider is quartically scaled, giving finer control at the low end where real FRC targets usually sit.
2. **Target Aspect Ratio** — width ÷ height of the bounding rectangle; discriminates target shape (tall vs. wide). Also nonlinearly scaled.
3. **Target Fullness** — percentage of active pixels inside the bounding rectangle; solid targets approach `1.0`, hollow/U-shaped targets read lower. Use this to reject partial detections that passed area/aspect-ratio by coincidence.
4. **Sort Mode** — how to pick among multiple contours that still pass every filter above. `closest` picks the one nearest the (calibrated) crosshair — usually what you want for aiming.
5. **Target Grouping** — enable dual/tri mode if your real target is made of multiple retroreflective shapes that should be tracked as one.
6. **Smart Speckle Rejection** — apply last, to reject small, close-range artifacts (e.g. LEDs). This is an outlier filter, not a primary one.

{% hint style="warning" %}
Lean on area/aspect-ratio/fullness to do the real work. Outlier rejection (speckle rejection, smart grouping) works *against* you if the individual filters are loose — it starts throwing away legitimate detections instead of noise.
{% endhint %}

## See Also

* [Tuning Workflow Overview](/documentation/tuning/tuning-workflow-overview.md)
* [Target & Pipeline Types](/documentation/understanding/target-and-pipeline-types.md) — `RetroreflectiveTape`, the typed result this pipeline feeds into `LimelightResults`.
* [Crosshair Calibration](/documentation/tuning/crosshair-calibration.md) — needed before "closest" sort mode means what you expect.


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