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If I got it right, this is a container format as an uncompressed ZIP archive. What is its advantage over zipped X3D, STL, DAE files?

Someone 8y ago
Uncompressed means you can mmap resources and directly use them (https://graphics.pixar.com/usd/docs/Usdz-File-Format-Specification.html https://graphics.pixar.com/usd/docs/Usdz-File-Format-Specifi...: ”A usdz file can contain only file types whose data can be consumed by the USD runtime via mmap or (eventually) pointer to memory.”) If you stored resources compressed, memory usage likely would go up, as you would need (part of) the compressed and the uncompressed resource in memory. Traditionally, that would be offset by decreased disk usage and faster I/O, but disks are a lot larger and a lot faster nowadays. Presumably, you would still download these files compressed (e.g. using http compression) Edit: further Dow, that page is clear that that’s the reason for not compressing chunks: ”A key consideration for efficient direct consumption of usdz files is that, given an archive already held in heap storage (possibly arriving over a network) or as a single file on disk, we be able to use the most direct API's available in USD for accessing the data contained within the archive, without extracting files to disk, or allocating more heap storage. If we allowed either compression or encryption in usdz archives, we would need to violate one or both of the preconditions that allow, for example, the usda and usdc formats to access their data via direct memory access (typically via mmap). We do not believe the lack of zip compression will be a serious concern for data size. Most image formats themselves allow internal compression schemes, and the usdc format is quite compact, particularly as you collect more data into a single file; although we do not yet have an end-user tool for doing so, USD now contains all of the core features we require to aggregate an arbitrary composition's worth of usd files into a single file, without removing any composition features from the scene.”
- niutech 8y ago
  How about other formats without compression, such as X3D, COLLADA?
  - taharvey 8y ago
    I've spent the last week trying to get good file transfer between two applictions, just for static 3D scenes - and I don't know if there isn existing file format. Heck, I can't even get two applications from Autodesk to wholly share a full 3D scene. If you know of a 3D file format that understand all types of geometry: Nurbs, solids, polygons AND physics based material shaders, AND understands whole scenes: lighting, cameras, and animation. Well I'd like to know of another one. Also this format adds futher concepts from a pipeline, things that are interesting to AR like late stage lighting, effects, composition, and overrides

Someone 8y ago

Uncompressed means you can mmap resources and directly use them (https://graphics.pixar.com/usd/docs/Usdz-File-Format-Specification.html https://graphics.pixar.com/usd/docs/Usdz-File-Format-Specifi...: ”A usdz file can contain only file types whose data can be consumed by the USD runtime via mmap or (eventually) pointer to memory.”) If you stored resources compressed, memory usage likely would go up, as you would need (part of) the compressed and the uncompressed resource in memory. Traditionally, that would be offset by decreased disk usage and faster I/O, but disks are a lot larger and a lot faster nowadays. Presumably, you would still download these files compressed (e.g. using http compression) Edit: further Dow, that page is clear that that’s the reason for not compressing chunks: ”A key consideration for efficient direct consumption of usdz files is that, given an archive already held in heap storage (possibly arriving over a network) or as a single file on disk, we be able to use the most direct API's available in USD for accessing the data contained within the archive, without extracting files to disk, or allocating more heap storage. If we allowed either compression or encryption in usdz archives, we would need to violate one or both of the preconditions that allow, for example, the usda and usdc formats to access their data via direct memory access (typically via mmap). We do not believe the lack of zip compression will be a serious concern for data size. Most image formats themselves allow internal compression schemes, and the usdc format is quite compact, particularly as you collect more data into a single file; although we do not yet have an end-user tool for doing so, USD now contains all of the core features we require to aggregate an arbitrary composition's worth of usd files into a single file, without removing any composition features from the scene.”

niutech 8y ago
How about other formats without compression, such as X3D, COLLADA?
- taharvey 8y ago
  I've spent the last week trying to get good file transfer between two applictions, just for static 3D scenes - and I don't know if there isn existing file format. Heck, I can't even get two applications from Autodesk to wholly share a full 3D scene. If you know of a 3D file format that understand all types of geometry: Nurbs, solids, polygons AND physics based material shaders, AND understands whole scenes: lighting, cameras, and animation. Well I'd like to know of another one. Also this format adds futher concepts from a pipeline, things that are interesting to AR like late stage lighting, effects, composition, and overrides