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

# rtcGetGeometryOppositeHalfEdge(3embree4)

### NAME

-

  ```
  rtcGetGeometryOppositeHalfEdge - returns the opposite half edge
  ```

### SYNOPSIS

-

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

### DESCRIPTION

The `rtcGetGeometryOppositeHalfEdge` function returns the ID of the opposite half edge of the specified half edge (`edgeID` argument) in the specified topology (`topologyID` argument). For instance in the following example the opposite half edge of `e6` is `e16`.

-

  ```

  ```

An opposite half edge does not exist if the specified half edge has either no neighboring face, or more than 2 neighboring faces. In these cases the function just returns the same edge `edgeID` again.

This function can only be used for subdivision geometries. The function depends on the topology as the topologies of a subdivision geometry have different index buffers assigned.

### EXIT STATUS

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

### SEE ALSO

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