<!--
{
  "availability" : [
    "iOS: 26.0.0 -",
    "iPadOS: 26.0.0 -",
    "macCatalyst: 26.0.0 -",
    "macOS: 26.0.0 -",
    "tvOS: 26.0.0 -",
    "visionOS: 26.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Metal",
  "identifier" : "/documentation/Metal/MTL4AccelerationStructureGeometryDescriptor/intersectionFunctionTableOffset",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "Metal"
    ],
    "preciseIdentifier" : "c:objc(cs)MTL4AccelerationStructureGeometryDescriptor(py)intersectionFunctionTableOffset"
  },
  "title" : "intersectionFunctionTableOffset"
}
-->

# intersectionFunctionTableOffset

Sets the offset that this geometry contributes to determining the intersection function to invoke when a ray intersects it.

```
var intersectionFunctionTableOffset: Int { get set }
```

## Discussion

When you perform a ray tracing operation in the Metal Shading Language, and provide the ray intersector object
with an instance of [`MTLIntersectionFunctionTable`](/documentation/Metal/MTLIntersectionFunctionTable), Metal adds this offset to the instance offset from structs such
as:

- [`MTLAccelerationStructureInstanceDescriptor`](/documentation/Metal/MTLAccelerationStructureInstanceDescriptor)
- [`MTLAccelerationStructureUserIDInstanceDescriptor`](/documentation/Metal/MTLAccelerationStructureUserIDInstanceDescriptor)
- [`MTLAccelerationStructureMotionInstanceDescriptor`](/documentation/Metal/MTLAccelerationStructureMotionInstanceDescriptor)
- [`MTLIndirectAccelerationStructureInstanceDescriptor`](/documentation/Metal/MTLIndirectAccelerationStructureInstanceDescriptor)
- [`MTLIndirectAccelerationStructureMotionInstanceDescriptor`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor)

The sum of these offsets provides an index into the intersection function table that the ray tracing system uses
to retrieve and invoke the function at this index, allowing you to customize the intersection evaluation process.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)