Network & formats

Network streaming

Data providers (src/data/) handle fetching brick data. The ShardedDataProvider uses HTTP Range requests to fetch individual bricks without downloading entire LOD files:

GET /datasets/volume/lod0.bin
Range: bytes=1835008-2122503
                │
                ▼
┌─────────────────────────────────────────┐
│ lod0.bin (concatenated brick data)      │
│ ┌─────┬─────┬─────┬─────┬─────┬─────┐  │
│ │  0  │  1  │  2  │  3  │ ... │ N   │  │
│ └─────┴─────┴──▲──┴─────┴─────┴─────┘  │
│                │                        │
│     Byte range for brick 2 only         │
└─────────────────────────────────────────┘

The index file (lod0_index.json) provides byte offsets, sizes, and pre-computed statistics:

json

{
  "entries": {
    "0/0/0": { "offset": 0, "size": 287496, "min": 0, "max": 45, "avg": 12.3 },
    "1/0/0": { "offset": 287496, "size": 287496, "min": 0, "max": 0, "avg": 0 }
  }
}

Empty brick detection: Before fetching, the loader checks if max < threshold. Bricks with no significant data are marked empty in the indirection table (LOD = 255) without any network request.

Network statistics are tracked in real-time:

Throughput: Rolling 2-second window of bytes/second
Total downloaded: Cumulative bytes since session start
Request count: Total HTTP requests issued

Brick compression

Bricks are stored with gzip compression to reduce network transfer size. A DecompressionPool of Web Workers handles parallel decompression without blocking the main thread:

Compressed Brick (HTTP) → Worker Pool → Decompressed Data → GPU Upload

Typical compression ratios:

Dense volumes (CT/MRI): 30-60% of original size
Sparse volumes (with empty regions): 10-30% of original size

The compression is transparent to the rest of the system—bricks are decompressed before being written to the atlas texture.

OME-Zarr streaming

The ZarrDataProvider (src/data/zarr-provider.ts) loads OME-Zarr volumes directly over HTTP using zarrita.js. A pool of Web Workers handles chunk fetching, decompression, and re-chunking into 66³ bricks with ghost borders. Since Zarr chunk boundaries don't align with Kiln's brick grid, workers fetch the overlapping chunks and assemble each brick from the relevant regions.

16-bit and float32 volume support

Kiln supports 8-bit unsigned, 16-bit unsigned, and 32-bit float volumes:

Feature	8-bit	16-bit integer	float32
Source dtype	`uint8`	`uint16`	`float32`
Texture format	`r8unorm`	`r16float`	`r16float`
Bytes per voxel (GPU)	1	2	2
Atlas size	~274 MiB	~548 MiB	~548 MiB
WebGPU feature	(none)	(none)	(none)

Windowing/leveling

16-bit data often uses only a portion of the full 0-65535 range. Windowing remaps a sub-range to the visible 0-1 output:

wgsl

fn applyWindow(density: f32, windowCenter: f32, windowWidth: f32) -> f32 {
    let halfWidth = windowWidth * 0.5;
    let minVal = windowCenter - halfWidth;
    return clamp((density - minVal) / windowWidth, 0.0, 1.0);
}

For example, a CT soft tissue window might use center=0.5, width=0.1 to expand a narrow intensity band to full contrast.

Network & formats ​

Network streaming ​

Brick compression ​

OME-Zarr streaming ​

16-bit and float32 volume support ​

Windowing/leveling ​