Live sheet
live.html streams one traced sheet (a tifxyz segment) and one scan volume (OME-Zarr: CT, or a 3D ink prediction)
straight from the Vesuvius Challenge open data bucket and shows the volume on the sheet in 3D. Nothing is packed
ahead of time and nothing is uploaded: your browser fetches only the rows of the segment inside the crop (HTTP Range)
and only the zarr chunks the samples touch, then samples and draws.
The sampling rule
Each node of the segment grid gets one value: the volume's voxels along the node's normal over plus or minus
Depth level-0 voxels, reduced by max or mean, reading the nearest voxel of the chosen pyramid level
(numpy rounding). This is the rule of kit sheetview in ChaseHendrick/Scrolls,
which writes the same mesh for Neuroglancer, and the two agree: on the PHerc0139 w045 preset (119,301 points) the
largest difference was 6e-6, and on a blosc-compressed 3D ink volume (350,761 points) it was 0. Refine grid
adds bilinear midpoints (a new node is valid when its cell's four corners are). Holes (-1) stay holes.
Inputs
| Field | URL parameter | Meaning |
|---|---|---|
| Segment | seg |
a tifxyz folder URL (x.tif, y.tif, z.tif, meta.json), uncompressed float32 in strips; the voxel size comes from the -NNum.tifxyz folder name |
| Volume | vol |
an OME-Zarr v2 root in the segment's voxels, raw or blosc, uint8 to float32 |
| Crop | crop=r0,r1,c0,c1 |
rows and columns of the segment grid |
| Volume level | level |
pyramid level; 1 halves the reads |
| Depth | depth |
voxels each side of the sheet |
| Refine grid | up |
1 to 4 |
| Along the normal | reduce |
max or mean |
| Colors | palette |
gray or ink |
autoload=1 |
load at once |
Example: /live.html?crop=500,650,700,900&level=1&depth=4&up=2&reduce=mean&autoload=1.
The presets are PHerc0139 w045 only, a public scan off the prize lists. Any public segment and volume in the bucket work, since the bucket answers CORS for GET and HEAD.
Outputs
- Download VTK: the mesh with its values as ASCII VTK, the format Neuroglancer's
vtk://source and ParaView read. - Volume in neuroglancer: the hosted Neuroglancer on the same volume.
An ink prediction shown here is model output, not a reading.
For agents
await liveSheet.load({ seg, vol, crop: [r0, r1, c0, c1], level: 1, depth: 4, up: 2, reduce: 'mean' });
liveSheet.state(); // params, vertices, triangles, chunks, samplesPerVertex, volume
liveSheet.values(); // the value of every grid node (NaN at holes)
liveSheet.turn(30); // orbit the camera, degrees
liveSheet.screenshot(); // PNG data URL
lib/livesheet.js has no DOM and runs in Node too: readSegment, upsample, normals, openVolume,
sampleSheet, sheetMesh, toVTK. Tests: node tests/livesheet.mjs (no network).
Limits
Zarr v3 volumes, zarr filters, compressed or tiled TIFFs are refused with a message. A crop of about 150 by 200 nodes refined twice is about 120,000 points and loads in about 15 s; the raw PHerc0139 CT at level 1 reads about 600 MB for it, so prefer level 2 for wide crops.