Hello all,
I am working on a custom field written with the Maya C++ API, inheriting from MPxFieldNode.
This field may have several particle systems plugged.
Brief version :
Is there any mean of accessing PP Attributes of *all* connected particle systems from MPxFieldNode::compute(), without causing their evaluation ?
Long version :
As a requirement to use some third party code, I need to know the total count of particles, aka, sum of all connected particle systems' particles count, + some pp attributes values, in order to allocate arrays of objects
This allocation should occur :
- in the first MPxFieldNode::compute call (We keep trace of current frame to avoid reiniting several times for several particle systems) to prepare arrays to be written.
- in the same frame I must be able to write data to these arrays.
I cannot allocate an array per particle system (third party code constraint), I need one array for all connected particles.
The issue : in the first compute, triggered by the first particle system, I'll try to access others particles plugged to crowdField, causing their evaluation. That generates a dependency loop, when building some MFnParticleSystem with connected objects.
I also tried accessing data through MDataBlock, but I can't manage to access pp attributes that way (let's say, lifespan for example) : mInputPPData seems to be used only for fieldName_attributeName data so its array is empty, mOwnerPPData does not give any attribute either. Moreover depending on how I fetch these arrays:
- as inputArrayValue, evalulations are requested on other particle systems
- as outputArrayValue, there is no evaluation but only particle system currently computed is accessible, access to others will crash.
Adding a re-entrance guard in the MPxFieldNode::compute can skip other particle systems compute() processing when counting particles, but does also tag them as 'clean", preventing them from calling their MPxFieldNode::compute at right time (field init for a particle system is done on a specific frame, which will be past at next call).
Is there any mean of accessing PP Attributes of *all* connected particle systems from MPxFieldNode::compute(), without causing their evaluation ?
Thank you for reading
