> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wherobots.com/llms.txt
> Use this file to discover all available pages before exploring further.
# ST_3DDWithin
Returns true if the 3D Euclidean distance between `A` and `B` is less than or equal to `distance`. Mirrors PostGIS `ST_3DDWithin`. Polymorphic over input type:
* `(Geometry, Geometry, Double)` — 3D distance via JTS; coordinates without a Z dimension are treated as `z = 0`.
* `(Box3D, Box3D, Double)` — closed-interval 3D distance between two axis-aligned cuboids. Throws `IllegalArgumentException` on inverted bounds (`xmin > xmax`, `ymin > ymax`, or `zmin > zmax`).
This is distinct from [ST\_DWithin](/reference/wherobots-db/geometry-data/predicates/ST_DWithin), which always measures planar (2D) distance regardless of input dimensionality — matching the PostGIS distinction between `ST_DWithin` and `ST_3DDWithin`.
Returns `NULL` if any argument is `NULL`.
## Signatures
```sql theme={"system"}
ST_3DDWithin(A: Geometry, B: Geometry, distance: Double)
```
```sql theme={"system"}
ST_3DDWithin(A: Box3D, B: Box3D, distance: Double)
```
## Parameters
The first geometry or 3D bounding box.
The second geometry or 3D bounding box.
The maximum 3D distance between `A` and `B`.
## Return type
`true` if the 3D distance between `A` and `B` is within `distance`.
## Example
```sql theme={"system"}
SELECT ST_3DDWithin(ST_PointZ(0, 0, 0), ST_PointZ(0, 0, 3), 3.0)
```
```
true
```
The same points are not within 2.9 units in 3D:
```sql theme={"system"}
SELECT ST_3DDWithin(ST_PointZ(0, 0, 0), ST_PointZ(0, 0, 3), 2.9)
```
```
false
```
## Optimization
`ST_3DDWithin(a, b, distance)` between two `Box3D` columns (or two geometry columns) is planned as a distance join. The planner expands each shape's XY footprint by `distance` for the R-tree pass — a valid superset filter, since the XY distance between two shapes is no greater than their 3D distance — and re-checks the full 3D distance per candidate pair.