How do I create an Alembic geometry Cache or animation from a series of meshes

[ourotu...@gmail.com]

I have a series of unique meshes that I would like to export to unreal and have them read as a geometry cache or animation. I have about 60 meshes and I would like each mesh to be a single frame of an animation. Basically, I want to create a 3D mesh flipbook asset for vfx.

The way I did this before was using 3ds max and unreals vertex animation tools script. https://docs.unrealengine.com/en-us/Engine/Animation/Tools/VertexAnimationTool

Is there a way I can do this with Alembic or any other way from blender.

I'm really stuck here so any help you guys can provide would be greatly appreciated.

[Lucas Miller]

If I'm understanding this correctly, there are 2 routes you could go.

Create one mesh, and then write the data for each of your unique
meshes to that one mesh per frame.
Another way is to create all 60 meshes, but animate visibility on each
one so it's only visible at the specific frames desired.

Hope this helps,

Lucas

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[ourotu...@gmail.com]

I already have all 60 meshes so I could animate visibility but how would that even export as a cache or anything useable in unreal. I thought visibility was program-specific. Is visibility even something that is stored in an Alembic file? I'm out of options so I can give it a try though

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[Lucas Miller]

Yes, visibility can be stored in the Alembic cache, and many popular
DCC apps can read and write it.

Lucas

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[ourotu...@gmail.com]

I'll give it a try then this will actually be a pretty decent workflow for the rest of my vfx stuff. Thanks

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[Rick Grandy]

Have you seen this?  We've used the Alembic plugin in UE4 with good success.

https://docs.unrealengine.com/en-us/Videos/PLZlv_N0_O1ga0aV9jVqJgog0VWz1cLL5f/rDHxxk0y2D4

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[ourotu...@gmail.com]

I can get simulations into unreal using alembic without an issue. The problem is that what I'm trying to do is basically a hand modeled simulation. Ive modeled each frame of the animation by hand and now need unreal to think its a simulation so it can play it back as one. Here is a low frame test of this that I did with the vertex tool animation script.

[Lucas Miller]

For this case why can't you feed each one of your hand modeled meshes into a single mesh at the correct time and then just write out that one mesh?

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[ourotu...@gmail.com]

I'd love to but I have no idea how.I'm just an environment artist with almost 0 experience with programming. I think thats what the vertex animation script I linked in my original post does however once I import into unreal I don't have much control over how the mesh. Its all done through a material node. Its not a very good way of doing things. Alembic seemed like it provided more control and a cleaner workflow but I don't know how to get what I have to be read as a geocache

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[Lucas Miller]

Hmmm, if you can feed each modeled mesh back into a single mesh per frame, and then just write out THAT one mesh out of your DCC (3ds max? Blender?)  then you wouldn't need any extra external script.

My other wacky ideas would involve a bit of programming to coral the individual meshes into a single one.

Lucas

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[ourotu...@gmail.com]

If I'm not mistaken this script does what you are suggesting.

https://docs.unrealengine.com/en-us/Engine/Animation/Tools/VertexAnimationTool/VAT_KF_Meshes

 It requires the resulting object to be exported as an FBX file. The advantage to this is that I can also rig all of the meshes and then create a physics asset in unreal. The issue is I have no control over how its played.

Alembic doesn't support a rig or skinned objects, right?

So far my experiments with keyframing the meshes haven't worked at all. I don't know how to feed the separate meshes into one. As I mentioned before I'm not a programmer and I am kind of out of my depth here.

I might have to look into this: http://www.sidefx.com/docs/houdini/io/alembic.html
What its describing there seems like what I need but I can't be sure until I get the software and do some tests.

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[alemb...@gmail.com]

I'm still struggling with UV's for each frame but I managed to use Alembic in Unreal quite easily using Maya without having too much experience in coding either. I hope that's an option for you and here's how I did it:

If you don't have your objects/animation in Maya already: I used this Plugin to Import large numbers of OBJs to Maya. https://www.highend3d.com/maya/script/free-obj-sequences-import-export-for-maya
This creates a sequence which can be exported via Cache/Alembic Cache/Export selection to alembic. You can then import this section into Unreal. Make sure to select "Geometry Cache" as the import type instead of Static. After dragging your alembic into the scene, select Running under Details and press play to check if it is working properly.

Unfortunately I don't know the approach for 3ds max but I hope I could help you. Since I can see your object is only using a uniform material, I assume you don't need specific UV's after the first frame. This is the part I'm struggling with, so I'll probably post a new topic...

[Alembic Fan]

Edit: If you have Maya you could of course just export your Frames from 3ds max as .obj and use my approach from there, but I'm sure there's a solution for 3ds max.

[ourotu...@gmail.com]

Thanks for the link. I'll definitely check it out. I use Blender and I think I read about a plugin that does the same thing your script does but for blender so I'll look into that as well. I was just using max because that's what the unreal script worked best in.
I've also gotten confirmation that this should be possible in Houdini alembic ROP (http://www.sidefx.com/docs/houdini/io/alembic.html#export)

This is another potential route I've come across (https://youtu.be/Kx4IU8lUCDs) I'll do some tests soon and let you know what, if anything worked.