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

# rtcInitPointQueryContext(3)

### NAME

-

  ```
  rtcInitPointQueryContext - initializes the context information (e.g.
    stack of (multilevel-)instance transformations) for point queries
  ```

### SYNOPSIS

-

  ```
  #include <embree4/rtcore.h>
  struct RTC_ALIGN(16) RTCPointQueryContext
  {
    // accumulated 4x4 column major matrices from world to instance space.
    float world2inst[RTC_MAX_INSTANCE_LEVEL_COUNT][16];
    // accumulated 4x4 column major matrices from instance to world space.
    float inst2world[RTC_MAX_INSTANCE_LEVEL_COUNT][16];
    // instance ids.
    unsigned int instID[RTC_MAX_INSTANCE_LEVEL_COUNT];
    // number of instances currently on the stack.
    unsigned int instStackSize;
  };
  void rtcInitPointQueryContext(
    struct RTCPointQueryContext* context
  );
  ```

### DESCRIPTION

A stack (`RTCPointQueryContext` type) which stores the IDs and instance transformations during a BVH traversal for a point query. The transformations are assumed to be affine transformations (3×3 matrix plus translation) and therefore the last column is ignored (see \[RTC\_GEOMETRY\_TYPE\_INSTANCE\] for details).

The `rtcInitPointContext` function initializes the context to default values and should be called for initialization.

The context will be passed as an argument to the point query callback function (see \[rtcSetGeometryPointQueryFunction\]) and should be used to pass instance information down the instancing chain for user defined instancing (see tutorial \[ClosestPoint\] for a reference implementation of point queries with user defined instancing).

The context is an necessary argument to \[rtcPointQuery\] and Embree internally uses the topmost instance transformation of the stack to transform the point query into instance space.

### EXIT STATUS

No error code is set by this function.

### SEE ALSO

\[rtcPointQuery\], \[rtcSetGeometryPointQueryFunction\]