---
name: "rtcSetGeometryBoundsFunction"
section: "3"
platform: "linux"
package: "libembree-dev"
version: "4.3.3+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/rtcSetGeometryBoundsFunction"
---

# rtcSetGeometryBoundsFunction(3)

### NAME

-

  ```
  rtcSetGeometryBoundsFunction - sets a callback to query the
    bounding box of user-defined primitives
  ```

### SYNOPSIS

-

  ```
  #include <embree4/rtcore.h>
  struct RTCBoundsFunctionArguments
  {
    void* geometryUserPtr;
    unsigned int primID;
    unsigned int timeStep;
    struct RTCBounds* bounds_o;
  };
  typedef void (*RTCBoundsFunction)(
    const struct RTCBoundsFunctionArguments* args
  );
  void rtcSetGeometryBoundsFunction(
    RTCGeometry geometry,
    RTCBoundsFunction bounds,
    void* userPtr
  );
  ```

### DESCRIPTION

The `rtcSetGeometryBoundsFunction` function registers a bounding box callback function (`bounds` argument) with payload (`userPtr` argument) for the specified user geometry (`geometry` argument).

Only a single callback function can be registered per geometry, and further invocations overwrite the previously set callback function. Passing `NULL` as function pointer disables the registered callback function.

In SYCL mode the BVH construction is done on the host and the passed function pointer must be a host-side function pointer.

The registered bounding box callback function is invoked to calculate axis-aligned bounding boxes of the primitives of the user-defined geometry during spatial acceleration structure construction. The bounding box callback of `RTCBoundsFunction` type is invoked with a pointer to a structure of type `RTCBoundsFunctionArguments` which contains various arguments, such as: the user data of the geometry (`geometryUserPtr` member), the ID of the primitive to calculate the bounds for (`primID` member), the time step at which to calculate the bounds (`timeStep` member), and a memory location to write the calculated bound to (`bounds_o` member).

In a typical usage scenario one would store a pointer to the internal representation of the user geometry object using `rtcSetGeometryUserData`. The callback function can then read that pointer from the `geometryUserPtr` field and calculate the proper bounding box for the requested primitive and time, and store that bounding box to the destination structure (`bounds_o` member).

### EXIT STATUS

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

### SEE ALSO

\[RTC\_GEOMETRY\_TYPE\_USER\]