BRL-CAD / brlcad

BRL-CAD is a powerful cross-platform open source combinatorial solid modeling system
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Converting Generic Twin results in different binary encodings cross-platform #114

Open brlcad opened 7 months ago

brlcad commented 7 months ago

There appears to be some subtle byte differences being written out into the geometry files during conversion, possibly from the fast4-g converter or perhaps from some librt processing/serialization difference. The files are byte-size identical. They differ in specific bytes. This difference is not expected nor typically observed during conversions.

Looking at hex dumps of two files, we find there are precisely 59 byte differences that are 1-3 values apart. This is possible indication the difference resides in the mantissa of certain floating point numbers that are differing by 1-3 ULP.

Examples of the two conversions and the corresponding hex dumps (via xxd) attached. GenericTwin.tar.gz