# Points

*A comprehensive guide to monitoring and analyzing flow properties at specific locations in the simulation domain using Points and Point Arrays.*

---

## Available Creation Methods

| *Type* | *Description* |
|--------|---------------|
| **Point** | Single monitoring location in 3D space |
| **Point array** | Multiple monitoring points along a straight line defined by its start and end points |
| **2D point array** | Points on a two-dimensional grid |
| **Group points** | A named group of explicitly listed points, typed in or imported from a CSV file |

---

## Detailed Descriptions

### Point

*Defines a single monitoring location in three-dimensional space for tracking flow properties.*

Point Parameters:
- **Position:** Three-dimensional coordinates (x, y, z)

### Point array

*Creates an array of equally spaced points between start and end locations.*

Point array Parameters:

- **Start Position:** Three-dimensional coordinates (x, y, z)
- **End Position:** Three-dimensional coordinates (x, y, z) 
- **Number of Points:**  Integer > 2 

### Group points

*Groups any number of explicitly listed points under one name.*

Create it with the **+** button of the Points group, which lists **Group points** after the other point types.

Group points Parameters:

- **Group name:** Name of the group
- **Coordinate system:** Coordinate system of the point coordinates (Global by default), chosen from the menu at the top of the panel
- **Points:** Table of points, each with a name and x, y, z coordinates. Add rows with the **+** button or import them from a CSV file with the import icon. The eye icon shows the points in the viewer.
- **Unit:** Length unit of the coordinates

The Python equivalent is `PointGroup`, with `PointGroup.from_csv` for CSV files.

<div align="center">

![GroupPoints](./Figures/group_points.png)

</div>

### Min/max locations

*Shows where the solver variables reached their extreme values, to help find the origin of a divergence.*

For a diverged case, the Points group lists **Min/max locations**. Its panel shows the minimum or maximum value and location of each tracked variable (for example `min_rho`, `min_p`, `max_umag`, `min_nuHat`, `max_nuHat`), with a pseudo-step slider to step through the history. The eye icon next to each variable shows its location in the viewer, which works in the Geometry, Mesh and Visualization tabs.

## Output Data

*Points and Point arrays provide access to flow field variables at their specified locations, allowing for detailed monitoring and analysis of local flow properties throughout the simulation.*

- Pressure
- Temperature
- Velocity components
- Density
- Turbulence quantities
- Vorticity
- Other solver-specific variables

```{note}
To monitor variables at points during a simulation, see [Probe Outputs](../02.simulation-setup/04.output/02.outputs-list/07.probe-outputs.md).
```

---

<details>
<summary><h3 style="display:inline-block"> ❓ Frequently Asked Questions</h3></summary>

- **Can points be placed outside the computational domain?**  
  > No, points must be positioned within the computational domain to provide valid results.

</details>

---

<details>
<summary><h3 style="display:inline-block"> 🐍 Python Example Usage</h3></summary>

```{seealso}
{py:class}`~flow360.Point`, {py:class}`~flow360.PointArray`, {py:class}`~flow360.PointArray2D`, {py:class}`~flow360.PointGroup`
```

```python
import flow360 as fl

# Create a single point at the leading edge
leading_edge_point = fl.Point(
    name="leading_edge",
    location=(1.0, 0.5, 0.0) * fl.u.m
)

# Create a point array for wake analysis
wake_profile = fl.PointArray(
    name="wake_profile",
    start=(0, 0, 0) * fl.u.m,
    end=(5, 0, 0) * fl.u.m,
    number_of_points=10
)

# Group many explicitly listed points under one name
rake = fl.PointGroup(
    name="rake_a",
    locations=[[0.0, 0.0, 0.0], [0.0, 0.0, 1.0]] * fl.u.m,
)

# Or read the coordinates from a CSV file, giving the unit and the x, y, z column names
probes = fl.PointGroup.from_csv(
    "probes.csv",
    name="rake_b",
    unit=fl.u.mm,
    coordinate_columns=("x_coord", "y_coord", "z_coord"),
)
```

`PointGroup.from_csv` reads a headerless file of exactly three columns when `coordinate_columns` is omitted, and drops repeated coordinates with a warning. A point group can be used in probe, surface probe and streamline outputs.
</details>