Querying start/end frame in an Alembic file

[Nicholas Yue]

Hi,

  In C++, what are the ways to query the start and end frame of an animated geometry in an Alembic file?

Cheers

[Alex Suter]

Something like this often works:

float fps = 24.0;

ISubDSchema schema = ...;

Alembic::AbcAbstract::TimeSamplingPtr ts = schema.getTimeSampling();

int numSamples = schema.getNumSamples();

float startTime = ts->getSampleTime(0);

float endTime = ts->getSampleTime(numSamples - 1);

float startFrame = startTime * fps;

float endFrame = endTime * fps;

It gets complicated for a number of reasons. Different objects in the cache could have different TimeSampling objects, they can be cyclic, acyclic, etc.

I've heard of people having success with just storing the start and end frames on their own as attributes, but that's pipeline specific.

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[Lucas Miller]

You can loop over the archives time samplings with the help of:

IArchive::getNumTimeSamplings
and
IArchive::getTimeSampling

And determine the maximum number of samples per time sampling via:
IArchive::getMaxNumSamplesForTimeSamplingIndex

Remember to skip the archive time sampling at 0. (default time sampling)

For more info see the functions near:
https://github.com/alembic/alembic/blob/master/lib/Alembic/Abc/IArchive.h#L150

Lucas

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