---
name: "rtcGetGeometryPreviousHalfEdge"
section: "3embree4"
platform: "linux"
package: "embree"
version: "4.4.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/rtcGetGeometryPreviousHalfEdge/3embree4"
---

# rtcGetGeometryPreviousHalfEdge(3embree4)

### NAME

-

  ```
  rtcGetGeometryPreviousHalfEdge - returns the previous half edge
  ```

### SYNOPSIS

-

  ```
  #include <embree4/rtcore.h>
  unsigned int rtcGetGeometryPreviousHalfEdge(
    RTCGeometry geometry,
    unsigned int edgeID
  );
  ```

### DESCRIPTION

The `rtcGetGeometryPreviousHalfEdge` function returns the ID of the previous half edge of the specified half edge (`edgeID` argument). For instance in the following example the previous half edge of `e6` is `e5`.

-

  ```

  ```

This function can only be used for subdivision geometries. As all topologies of a subdivision geometry share the same face buffer the function does not depend on the topology ID.

### EXIT STATUS

On failure an error code is set that can be queried using `rtcGetDeviceError`.

### SEE ALSO

\[rtcGetGeometryFirstHalfEdge\], \[rtcGetGeometryFace\], \[rtcGetGeometryOppositeHalfEdge\], \[rtcGetGeometryNextHalfEdge\], \[rtcGetGeometryPreviousHalfEdge\]