With UGCUSE3DSERVICES=7:0 (the client's default) the client asks its world for
a blueprint file's MD5 and size (REQUEST_UGC_MANIFEST_INFO, world 27) and then
downloads BrickModels/UserMade/<id % 1000>/<id>.<ext>.sd0. Layouts checked in
the 1.10.64 client: the request is a u64 blueprint id and a u8 resource type;
the answer (UGC_MANIFEST_RESPONSE, client 60) repeats them and adds a u8 valid,
the u32 size and the 16 byte MD5 of the inflated file, 37 bytes after the 0x53
exactly or the client drops it.
- dNet: WorldPackets::RequestUgcManifestInfo, ClientPackets::UgcManifestResponse
(eUgcResourceType), with byte tests against the client's layouts.
- Database: ugc_file_checksums (per model or module combination and file) and
ugc_modular_build.combination_id (migrations 89 / 72), GetUgcFileChecksum
looks a blueprint up as a model, else as a build through its combination.
- UGC server: every download is also written as .sd0 (Sd0::Compress); workers
hand the checksums back and the main thread stores them; old items get their
sd0 icon and checksum, and builds their combination id, once at start-up, a
few per tick; serves <dir>/BrickModels/UserMade/<bucket>/<id>.<ext>.sd0 under
client_path, /<folder>/UserBrickModels and the root (.hkx 404).
- World: UgcManifest answers on the main thread with one indexed query per
request; files not made yet are answered when they are (looked at again
every 5 seconds), and a model in its quiet period is made right away. No
worker threads, HTTP or file reads in the world.
Off by default (ugc_manifest=0): checked in game, the client then downloads
from http://127.0.0.1:80/lwoclient/UserBrickModels/ whatever its boot.cfg says
and logs the player out when it can't connect, so icons need the UGC server on
port 80 of each player's machine. docs/UgcServer.md has the details.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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