RTC_GEOMETRY_TYPE_INSTANCE - instance geometry type
#include <embree3/rtcore.h> RTCGeometry geometry = rtcNewGeometry(device, RTC_GEOMETRY_TYPE_INSTANCE);
Embree supports instancing of scenes using affine transformations (3×3 matrix plus translation). As the instanced scene is stored only a single time, even if instanced to multiple locations, this feature can be used to create very complex scenes with small memory footprint.
Embree supports both single-level instancing and multi-level instancing. The maximum instance nesting depth is
RTC_MAX_INSTANCE_LEVEL_COUNT; it can be configured at compile-time using the constant
EMBREE_MAX_INSTANCE_LEVEL_COUNT. Users should adapt this constant to their needs: instances nested any deeper are silently ignored in release mode, and cause assertions in debug mode.
Instances are created by passing
RTC_GEOMETRY_TYPE_INSTANCE to the
rtcNewGeometry function call. The instanced scene can be set using the
rtcSetGeometryInstancedScene call, and the affine transformation can be set using the
Please note that
rtcCommitScene on the instanced scene should be called first, followed by
rtcCommitGeometry on the instance, followed by
rtcCommitScene for the top-level scene containing the instance.
If a ray hits the instance, the
primID members of the hit are set to the geometry ID and primitive ID of the hit primitive in the instanced scene, and the
instID member of the hit is set to the geometry ID of the instance in the top-level scene.
The instancing scheme can also be implemented using user geometries. To achieve this, the user geometry code should set the
instID member of the intersection context to the geometry ID of the instance, then trace the transformed ray, and finally set the
instID field of the intersection context again to -1. The
instID field is copied automatically by each primitive intersector into the
instID field of the hit structure when the primitive is hit. See the [User Geometry] tutorial for an example.
For multi-segment motion blur, the number of time steps must be first specified using the
rtcSetGeometryTimeStepCount function. Then a transformation for each time step can be specified using the
See tutorials [Instanced Geometry] and [Multi Level Instancing] for examples of how to use instances.
NULL is returned and an error code is set that can be queried using
[rtcNewGeometry], [rtcSetGeometryInstancedScene], [rtcSetGeometryTransform]