# init(positions:coefficients:tetrahedronIndices:) Creates a diffuse probe resource from arrays of probe data. ``` nonisolated convenience init(positions: [SIMD3], coefficients: [InlineArray<3, SIMD4>], tetrahedronIndices: [SIMD4]) throws ``` ## Parameters `positions` The 3D positions of each probe, in local space relative to the probe group entity. Must contain at least 4 positions to form a valid tetrahedral mesh. `coefficients` Spherical harmonic coefficients for each probe. Each entry contains exactly 3 `SIMD4` values — one per RGB channel, ordered as `(L0, L1.x, L1.y, L1.z)`. Must have the same count as `positions`. `tetrahedronIndices` Indices defining the tetrahedral mesh connectivity. Each `SIMD4` references 4 probe positions by index into `positions`. Must contain at least 1 tetrahedron, and all indices must be less than `positions.count`. ## Discussion> Throws: An error if the data is invalid — for example, if `positions.count` and > `coefficients.count` differ, if fewer than 4 probes are provided, or if any > tetrahedral index is out of bounds. --- Copyright © 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)