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Esri / i3s-spec

This repository hosts the specification for Scene Layers which are containers for arbitrarily large amounts of geographic data. The delivery and persistence model for Scene Layers, referred to as Indexed 3d Scene Layer (I3S) and Scene Layer Package (SLPK) respectively, are specified.
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3D object geometry format undocumented? #57

Closed barf closed 4 years ago

barf commented 4 years ago

I am unable to find the specification for the binary geometry format indicated in 3D object and mesh SceneLayers.

Can someone point to me where I can find documentation on this file format?

In practice the content-type is application/octet-stream and it is delivered as a .bin - I'm guessing it's a TLV format reminiscent of ASN.1 but unable to find any official information about this ".bin" format.

This is the data I'm trying to work with:

$ hexdump -C 0.bin |head
00000000  1b 0f 00 00 1f 00 00 00  05 36 02 ba 9b 12 ab b8  |.........6......|
00000010  d5 5e 5c 41 60 4c 05 ba  1d b9 b0 b8 d5 5e 5c 41  |.^\A`L.......^\A|
00000020  f2 8b 01 ba 73 b2 b7 b8  d5 5e 5c 41 86 b4 08 ba  |....s....^\A....|
00000030  fa 5f b1 b8 3e 5f 5c 41  c4 17 0a ba 4f 84 9c b8  |._..>_\A....O...|
00000040  3e 5f 5c 41 4f 1f 0b ba  ba 24 b8 b8 d5 5e 5c 41  |>_\AO....$...^\A|
00000050  ce df ff b9 05 9e 97 b8  3e 5f 5c 41 60 4c 05 ba  |........>_\A`L..|
00000060  1d b9 b0 b8 d5 5e 5c 41  05 36 02 ba 9b 12 ab b8  |.....^\A.6......|
00000070  d5 5e 5c 41 83 98 0b ba  a6 78 55 b8 3e 5f 5c 41  |.^\A.....xU.>_\A|
00000080  ce df ff b9 05 9e 97 b8  3e 5f 5c 41 4d 87 f5 b9  |........>_\AM...|
00000090  9e 25 75 b8 3e 5f 5c 41  b6 94 f2 b9 dd 98 64 b8  |.%u.>_\A......d.|
ajuanr commented 4 years ago

The .bin file is not a new format, but simply a binary file.

The first 8 bytes of this file are the header. The byte order is little endian. The first 4 bytes (0x00000F1B = 3867) is the number of vertices. The next 4 bytes (0x0000001F = 31) is the number of features.

More information on the geometry buffer can be found here: https://github.com/Esri/i3s-spec/blob/master/docs/1.7/geometryBuffer.cmn.md