Replace geometry from imported Animation

[Brouwers]

Hello all!

Hopefully someone can help me with the following:
I'm using VDB-textures to create something that looks like smoke moving through pipes. I created the animations for this in Blender.
The geometry I used for the VDB-textures are spheres, also imported from Blender. I want to use displace nodes to animate the geometry changing in size (so that it fits through the pipes, which are getting smaller), but this creates some weird grids.
I looks like this happens, because the geometry is imported. The grid doesn't appear with native Keyshot geometry.

Is it possible to replace the imported geometry with Keyshot geometry?

Thank you!

[Eugen Fetsch]

Hope that I understood it right...
You would need to do all the geometry work in Blender (animation and displacement) and import everything through Alembic to KS. VDB animation is not supported in KS yet.
But is it really necessary to render smoke in KS? How about to render it in Blender EEVEE and compose it over the KS render in Resolve or After Effects? It will save you a lot of time. You can use the KS clown pass to mask out the smoke. 

[Brouwers]

Thank you for your response!

I managed to find a simple way around my initial problem. I just added Keyshot spheres and copied the position and imported animation over to those. The grid is now gone and I can animate the size of the spheres.
But you raise a good point. The VDB textures can't be animated (yet) in Keyshot, so the little puffs of smoke moving through the pipes look very odd and not realistic at all.

Unfortunately I'm not that experienced with Blender and I don't have too much time to try a lot of different things. Wouldn't it be an enormous hassle to render the smoke in Blender, because you'd have to get it at the exact same perspective and angles to be able to compose it over the Keyshot animation?

[Eugen Fetsch]

The KS scene can be exported to FBX, including all the cameras. It will work to match the exact perspective or angle, as long as the cameras do not have any animation applied. KS cannot export camera animation, so be aware of that.
If you need to match the camera movement in both applications, you would need to animate the camera in Blender and then import it through Alembic to KS. Don't use FBX for this workflow - FBX is buggy and you'll have some weird jumps between keyframes.

To export the scene cameras you need at least one simple cube or plane to be visible in the scene.

I don't know a better way to get the job done quicker. If you look into the VFX industry - all smoke sims are done seprately and composed into the scene in post afterward.
Hevy geometry + smoke sims in one scene = billions and billions of samples to be noisefree 
Both rendered seperately is more simple to handle and to denoise.

[Brouwers]

I see, thank you.
I might already try creating the smoke animations for my current project. I do have some animated camera's in there. But after replicating the paths of the camera's in Blender, why would I want to export them back to Keyshot? If I understand correctly, I would have to animate and render the smoke in Blender. Then use it for post processing, right?
The keyshot animation then doesn't have any of the smoke effects. Like you say, to render them seperately.

Because that indeed scares me: having to render billions of samples. I only have 26 cores at my disposal, so it probably would take more than a month of non-stop rendering.
Trying to render the smoke seperately from Keyshot seems like a great idea!

Thanks

[Eugen Fetsch]

But after replicating the paths of the camera's in Blender, why would I want to export them back to Keyshot? If I understand correctly, I would have to animate and render the smoke in Blender. Then use it for post processing, right?

Yes, yes and yes. You would need to reimport the camera into KS only then, if it has some advanced path animation, tilt animation (not available in KS) or you need to be very precise. Otherwise you don't need to do that.

Because that indeed scares me: having to render billions of samples. I only have 26 cores at my disposal, so it probably would take more than a month of non-stop rendering.
Trying to render the smoke separately from Keyshot seems like a great idea!
Thanks

glad to be helpful. Would love to see your result in "Amazing Animation"