So I have been stuck on this for a month or so on and off having time on the weekends.

I am trying to fracture a large boulder in my scene..

I am using RBDMaterialFracture node and did get a nice result starting with a simple test cube

Doing this tutorial here....

https://www.youtube.com/watch?v=VXaBMM7rOqY&t=886s [www.youtube.com]

....and later with this info...
worked my way up to a large boulder with some detail.

I realized I was being too ambitious with breaking apart the whole boulder geometry and so I opted to only shatter the front area so that I could save on calculation/sim time but now am running into a different set of problems further down the testing road.

One of the issues with my first test was that though I did get a nice test shatter I did not have consistent UVs from Maya > Houdini > back to Maya with Alembic as the animation cache format.

So I setup specific UVs so I could match my displacement object. Even baked in the displacement to the mesh so it would shatter at render time the same shape as the displaced original mesh..

So far so good.

Problem is that though I did get the object and UV into Houdini... I am having trouble working out where I can solve this UV on the interior pieces without changing the exterior pieces UV as I keep getting parts disappearing in the process.

Also even though I have had some success testing the UVautoSeam and UVFlatten nodes to deal with the interior UVs being mapped after the fracture... I am not sure how I plug it all back in after I get these results so that it all stays consistent post the sim and cache.

1st issue is just getting the RBD material fracture to stop losing pieces.

2nd issue is where do I plug the uv-nodes after I chain them out of the RBDmaterialFracture node?

Just plugging them into the rbd configure below it seems to lose the UVs again.

I currently have them like this but it doesn't seem to matter when I write the file.

I finally arrived at the magical numbers that stopped most of the weird issues above.

Now I am at the export stage and can't seem to get an Alembic written that has the UVs still intact.

I can see that my previous experiment with plugging the UVAutoSeams and UVFlatten did work as I can see the data post the FileCache node but I couldn't make it write an Alembic that wouldn't freeze Maya on import at first.

I tried using the convert node and it did make it so that the Alembic import in Maya worked right away, takes longer to convert but works.

BUT.. the alembic, while it animates fairly well (meaning refresh time scrubbing the time line) for such a large data set it does not have the UV info intact.

It seems the convert node may be getting usable polygon info but it does something to the UV information..

In Maya it shows up as a bunch of nested groups in the UV window but I can't find any UV info.

Here is the info on the convert node... I see the UV 3flt.. isn't that my UV info?

Ok, I finally was able to get this to work and thought I would leave it here since I didn't get any responses.. in case the other four people on Earth that will work this way some day may look for it.

I am not exactly sure why it works but I fiddled around with different ideas about attaching information to the data before it ended up in the Cache.

Previously I was doing the (Convert) node from "All to Polygon Soup" after the Sim Cache.

I also was just using the default Outside/Inside/Chipping etc groups that the RBD Material Fracture creates.
Instead this time I applied materials Outside and Inside using those predefined groups to see if they would help Maya see information about the faces assigned after the UV process.

Somehow this ends up with a successful Alembic bake that doesn't crash Maya on import AND... with UVs.