[dependencies]
ply = "^0.2.3"

ply

Write and view PLY point clouds, in pure NURL.

ply view cloud.ply            # serve a WebGL viewer on localhost:8080
ply info cloud.ply            # print the header
ply cloud.ply                 # shorthand for view

The writer

Streaming: the vertex count is not known until the last point, so the header goes out with a fixed-width placeholder and is patched in place at the end. Nothing is held in memory.

$ `deps/ply/src/ply.nu`

?? ( ply_create `cloud.ply` 0 `my-tool 1.0` ) {   // 0 = binary, 1 = ascii
    T w → {
        ( ply_vertex w 0.0 1.0 2.0  255 128 0 )   // x y z  r g b
        ...
        ? ( ply_finish w ) {} { /* the file cannot be trusted */ }
    }
    F e → { ... }
}

The layout is x,y,z float32 + red,green,blue uchar — 15 bytes a vertex in binary_little_endian, one line a vertex in ascii. MeshLab, CloudCompare, Blender and f3d all open it.

The viewer

One self-contained WebGL2 page, compiled into the binary (an installed tool has no views/ directory; --page FILE overrides it while editing the page). It serves GET / (the page) and GET /cloud (the file, verbatim) and draws with orbit / pan / zoom, point-size, density and far-trim sliders, and rgb / height / depth colouring.

Details that matter more than they look:

• Points are shuffled once with a seeded Fisher-Yates, so the density

slider draws a uniform sample of the scene instead of a prefix of the write order.

• The far-trim slider is a percentile of distance from the centre,

not a distance to guess; reconstruction clouds put sky at plausible but enormous depths, and the default keeps the farthest 2 % out.

• World up defaults to -Y: reconstruction clouds are usually in

OpenCV camera axes (x right, y down, z forward).

• ?yaw=&pitch=&dist=&roll=&trim=&ps= pin a view, for linking or for a

test; ?probe=N renders N frames and reports the lit-pixel count so a headless test can check what the GPU actually drew.

$ `deps/ply/src/view.nu`

( vw_serve `cloud.ply` `127.0.0.1` 8080 `` 0 )   // serves until killed

Tests

./tests/ply_test.sh

Writer round-trip (binary vs ascii agree, count patched, oracle-parsed), the server (page + cloud verbatim), and — when chrome/chromium is on PATH — a real headless render with a lit-pixel assertion.