terminals_core/substrate/
splat.rs

1//! SplatProjection — Visual/Semantic embedding (384-dim float32).
2//!
3//! Maps to the RadianceField gaussian splat rendering and HNSW semantic space.
4//! The embedding is the atom's position in the 384-dim semantic manifold.
5
6use super::projection::{Projection, ProjectionId};
7
8/// Embedding dimensionality (matches mesh-sink normalization in TS).
9pub const EMBEDDING_DIM: usize = 384;
10
11/// Byte size: 384 × 4 bytes = 1536 bytes.
12const SPLAT_BYTES: usize = EMBEDDING_DIM * 4;
13
14#[derive(Debug, Clone)]
15pub struct SplatProjection {
16    pub embedding: [f32; EMBEDDING_DIM],
17}
18
19impl Default for SplatProjection {
20    fn default() -> Self {
21        Self {
22            embedding: [0.0; EMBEDDING_DIM],
23        }
24    }
25}
26
27impl Projection for SplatProjection {
28    fn byte_size() -> usize {
29        SPLAT_BYTES
30    }
31
32    fn id() -> ProjectionId {
33        ProjectionId::Splat
34    }
35
36    fn read(buf: &[u8]) -> Self {
37        assert!(buf.len() >= SPLAT_BYTES, "SplatProjection: buffer too small");
38        let mut embedding = [0.0f32; EMBEDDING_DIM];
39        for i in 0..EMBEDDING_DIM {
40            let offset = i * 4;
41            embedding[i] = f32::from_le_bytes([
42                buf[offset],
43                buf[offset + 1],
44                buf[offset + 2],
45                buf[offset + 3],
46            ]);
47        }
48        Self { embedding }
49    }
50
51    fn write(&self, buf: &mut [u8]) {
52        assert!(buf.len() >= SPLAT_BYTES, "SplatProjection: buffer too small");
53        for i in 0..EMBEDDING_DIM {
54            let bytes = self.embedding[i].to_le_bytes();
55            let offset = i * 4;
56            buf[offset..offset + 4].copy_from_slice(&bytes);
57        }
58    }
59
60    fn shape_hash_contribution(&self) -> u32 {
61        // FNV-1a over first 16 floats (enough for shape identity without full 384-dim scan)
62        let mut hash = 0x811c_9dc5u32;
63        for &v in &self.embedding[..16.min(EMBEDDING_DIM)] {
64            let bits = v.to_bits();
65            for byte in bits.to_le_bytes() {
66                hash ^= byte as u32;
67                hash = hash.wrapping_mul(0x0100_0193);
68            }
69        }
70        hash
71    }
72}
73
74#[cfg(test)]
75mod tests {
76    use super::*;
77
78    #[test]
79    fn test_splat_byte_size() {
80        assert_eq!(SplatProjection::byte_size(), 1536);
81    }
82
83    #[test]
84    fn test_splat_roundtrip() {
85        let mut proj = SplatProjection::default();
86        proj.embedding[0] = 1.0;
87        proj.embedding[100] = -0.5;
88        proj.embedding[383] = 0.42;
89
90        let mut buf = vec![0u8; SplatProjection::byte_size()];
91        proj.write(&mut buf);
92        let restored = SplatProjection::read(&buf);
93
94        assert!((restored.embedding[0] - 1.0).abs() < 1e-6);
95        assert!((restored.embedding[100] - (-0.5)).abs() < 1e-6);
96        assert!((restored.embedding[383] - 0.42).abs() < 1e-6);
97    }
98
99    #[test]
100    fn test_splat_shape_hash_varies() {
101        let a = SplatProjection::default();
102        let mut b = SplatProjection::default();
103        b.embedding[0] = 1.0;
104        assert_ne!(a.shape_hash_contribution(), b.shape_hash_contribution());
105    }
106}
terminals_core/substrate/splat.rs

terminals_core/substrate/
splat.rs
