What the Constellation Signature Is

The constellation signature is an optional, supplementary component of a content artifact's unique identifier (UID) record. It is a geometric fingerprint derived from the relative positions and angular relationships of high-salience spatial anchor points detected within the content, computed in a manner invariant to translation, rotation, and uniform scale change. It is distinct from and supplementary to the variance-vector-based UID: where the variance vector encodes distributional variance across the artifact, the constellation signature encodes spatial relational geometry. The two are not interchangeable, and the constellation signature is emitted only when the content presents enough distinct salient structure to support it.

Its purpose is narrow and specific. The constellation signature supports matching of artifacts that share a distinctive spatial composition across cropping, scale change, and partial occlusion. Together with the structure signature, which supports recognition of logos, icons, and graphically sparse artifacts across background color changes and flat-fill variations, it serves the specialized matching functions that the global nine-dimensional variance vector and the four quadrant fingerprints do not capture on their own.

Saliency Hotspot Detection

The signature begins with saliency hotspot detection over the canonical image. The detector scores a coarse 12x12 grid, computing for each cell a saliency value equal to twice the cell's intra-cell intensity variance plus its mean local gradient density. Cells are sorted by descending score, and up to five spatially distributed high-salience anchor points are selected. A minimum inter-cell separation of one grid unit is enforced during selection, which prevents multiple hotspots from clustering on a single prominent feature and preserves the geometric diversity the constellation depends on.

At least three hotspots are required for the constellation signature to be computed. If fewer than three are detected, the constellation signature is not emitted and the corresponding field in the UID record is null. This is the disclosed gating condition: there is no fixed target count beyond the up-to-five ceiling and the three-hotspot floor, and there is no notion of an arbitrarily large anchor set.

Micro-Constellation Descriptors

The micro-constellation computation stage builds an independent descriptor for each detected hotspot. Each hotspot in turn serves as a focal anchor, and its nearest neighbors among the remaining hotspots are identified by Euclidean distance. The distances from the focal anchor to its neighbors are normalized by the maximum pairwise inter-hotspot distance within the image, which renders the constellation scale-invariant. The normalized distances are quantized into eight bins.

Angles are computed between the vector from the focal anchor to its nearest neighbor and each subsequent neighbor vector, in the range zero to pi radians. Measuring angles relative to the nearest-neighbor direction, rather than to a fixed image axis, makes the constellation rotation-invariant. These angular values are quantized into twelve bins of fifteen degrees each. A descriptor string encoding the hotspot grid coordinates, the quantized distances, and the quantized angles is then hashed with a sixty-four-bit FNV (Fowler-Noll-Vo) variant to produce a micro-constellation hash for that focal anchor.

Order-Invariant Aggregation

The per-hotspot micro-constellation hashes are aggregated in a way that erases any dependence on detection order. The rotation-invariant micro-hash aggregation module sorts the set of per-hotspot hashes lexicographically, so that the constellation hash does not depend on the order in which hotspots were detected or processed. The sorted hashes are concatenated and hashed using the structure hash function to produce a 256-bit constellation hash, which is extended to a 320-bit constellation identifier by the multi-segment FNV-64 combiner.

The lexicographic sort is the same order-invariance technique used elsewhere in the platform, including the rotation-invariant sorting of the four quadrant hashes during 320-bit UID construction. It is a deterministic sorting step, not a cryptographic reconstruction scheme: the signature is a hash of a sorted set of geometric descriptors, computed deterministically from the content's detected salient geometry.

Pairing With the Structure Signature

The constellation identifier is paired with the structure identifier to derive a routing handle. The structure signature is computed in parallel: a gradient-only structure vector of twenty-one dimensions is derived exclusively from spatial gradient information, suppressing sensitivity to mean luminance and background fill, and is hashed and extended to a 320-bit structure identifier. The anchor ID module derives a non-authoritative 128-bit anchor identifier from the 320-bit structure identifier and the 320-bit constellation identifier by applying the multi-segment combiner to their concatenation and retaining the first two 64-bit segments.

This anchor ID is a compact routing handle for content objects whose structure and geometric composition are intended to match across background substitution, format conversion, and partial cropping, as commonly encountered in logo recognition, reverse image search, and derivative content attribution workflows. The disclosure describes it as non-authoritative: it is a handle for grouping and lookup, not a cryptographic assertion of identity or ownership.

The Invariances It Provides

Each construction choice maps to a specific invariance. Normalizing inter-anchor distances by the maximum pairwise distance gives scale invariance. Measuring inter-anchor angles relative to the nearest-neighbor direction gives rotation invariance. Working from relative positions rather than absolute image coordinates gives translation invariance. Because the signature is built from a small set of distributed salient points and their pairwise relationships, a crop or partial occlusion that removes some of the scene can still leave a recognizable subset of the original spatial composition, which is why the constellation signature is the component designated for matching across cropping, scale change, and partial occlusion.

These are the disclosed invariances, derived directly from the geometry of the construction. The disclosure does not describe geometric distortion tolerances expressed as residual thresholds on fitted transformations, nor any reconstruction of a transformation during matching; quantization into the disclosed distance and angle bins is the mechanism by which bounded geometric variation is absorbed.

Role Within the Identity Record

The constellation signature does not stand alone as a content identity. The primary identity of an artifact is the 320-bit UID, constructed from the global nine-dimensional variance vector and the four rotation-invariantly sorted quadrant hashes. The structure signature and constellation signature are optional fields carried alongside that UID, supplying specialized matching for cases the variance-based UID does not address: graphically sparse logos and icons for the structure signature, and distinctive spatial compositions surviving crop, rescale, and occlusion for the constellation signature. When the content lacks three detectable hotspots, the constellation field is simply null and identity proceeds from the variance-derived UID alone.

Because the constellation identifier is a 320-bit value in the same width as the UID and the structure identifier, it integrates with the platform's slope-indexed anchor registration and distributed lookup without special handling. It is registered, routed, and compared as one more slope-bearing fingerprint, contributing geometric matching reach to a content anchoring layer whose authoritative identity remains the variance-derived UID.

Disclosure Scope

The constellation signature, comprising saliency hotspot detection over a 12x12 coarse grid scored as twice intra-cell intensity variance plus mean local gradient density, selection of up to five spatially separated hotspots with a three-hotspot minimum below which the signature is null, per-hotspot micro-constellation descriptors built from nearest-neighbor inter-anchor distances normalized by the maximum pairwise distance and quantized into eight bins and rotation-invariant angles quantized into twelve fifteen-degree bins, sixty-four-bit FNV hashing of each descriptor, lexicographic aggregation of the per-hotspot hashes into a 256-bit constellation hash extended to a 320-bit constellation identifier, and derivation of a non-authoritative 128-bit anchor ID from the structure and constellation identifiers, is disclosed in PCT International Application No. PCT/US26/28630 in the section on structure and constellation signatures. This article describes that disclosed mechanism.

The scope is limited to what the disclosure supports: a deterministic, translation-, rotation-, and uniform-scale-invariant geometric fingerprint that is an optional, supplementary component of the variance-derived UID record, serving spatial-composition matching across cropping, scale change, and partial occlusion. The disclosure does not describe, and this article does not assert, any threshold-tolerant cryptographic binding, secret sharing, threshold signature, accumulator commitment, k-of-N reconstruction, per-anchor revocation, or append-only verification lineage as part of the constellation signature.