You're starting to delve into intrinsic transform land so I'll give a brief primer just in case. A packed prim's transforms are stored as intrinsic primitive attributes. The ones we care about are pivot and transform because you can change those. The others are immutable. You can also see the changes to those values through the point attributes P, pivot and orient. And you can change the point attributes which will update the intrinsic attributes. It can get a little confusing sometimes because changing one, changes the other.

So, the vertex animation texture tool is looking at the point attributes. The transform pieces node effects the intrinsic transforms but zeros out the orient attribute. Turn on Copy Template Attributes and add orient to pass that attribute through. That should get it working with the VAT exporter.

There are a number of ways to animate individual pieces. If you just want to do it by hand. You can put down a transform sop after your object_merge1 and manually translate and rotate a single piece by setting the group parm to the number of the packed prim you want to effect. The transform sop will update the intrinsic transforms as well as the orient attribute so it should work with exporting to a texture.

Mike

Hi DG,

Can you expand on why the video is no longer relevant? The basic premise is that you can create velocity fields in a number of ways in Houdini. The tool just helps export that into the fga format UE4 is expecting.

Mike

Hi folks. I've created some basic mesh generators for realtimevfx so that you can hopefully stay in the game engine and still create the kind of geo you would use in a particle system. Looking for feedback.

Okay. This is silly it's so simple. Change your import style on the dopimport to “Fetch Geometry from DOP Network” and it will work. I'm going to speak to the team tomorrow to figure out what's happening under the hood since I'm sure I was the one that suggested you use fetch packed geo.

Mike

Wanted to keep you in the loop. I thought it would be a quick fix but I think you've highlighted an underlying issue with how we normalize and then expand both the centroid and the position data. It doesn't happen with all setups and there's no immediate fix. I'll get back to you when I have something.

What is the error on the timewarp? It could be that you're trying to access a frame value that isn't available for that sequence so it fails. You probably need to clamp the value.

Also, do you want to see both sims at the same time or one after the other? If they should be sequential then use a switch and set a key on the switch to swap between the one and the other.

Mike

What values are you using for your bbox min and max? If it's greater than 1000 then you're probably running into floating point precision issues. You could try scaling the sim down but you'd need to check rest, orient and pivot attributes as well (and possibly intrinsic transform).

We've considered another export method that use 2 pixels per position value but I haven't had a chance to test it out and implement it.

Mike

Because you're importing directly from the AutoDopNetwork it's grabbing the ground as well which isn't a packed object.

Better to use a dopimport in a geo container and specify that you just want the Box_Fracture object imported as packed geo.

I think you can ignore the warnings. Those are specific to 16.5 but shouldn't cause any problems.

Brian, can you share your test file?

Mike

Sorry about that! I thought I'd uploaded that file but I see now that it had failed.

Hey Phillip,

Sorry about the delay. I've attached an example file that should work for you.

I ended up recreating the rig because there's no easy way to match the scale in and out of Houdini. If you got that to work then great!

Things to keep in mind:
*The rootNULL needs to be oriented correctly. So rotate -90 in x and then clean transforms. If you middle click on the node in my example you'll see the values in the world transform section.
*Make sure “Create Root for Subnet” is turned on in your fbx export settings.
*To do a rigid bind you can use a capture override based on groups.
*I think you need to ‘force recapture’ after you've moved the joints and mesh around. So move the joint then the mesh and the force recapture.

Mike

Hey Graham,

Sounds like the texture isn't being generated which could be because of the path you've set for the export node. Make sure it's pointing to the object level node not the sop level node.

You can also right click on the VAT hda and choose “allow editing of contents”. Then dive inside and find fluid_copnet/calculate_delta node and make sure it's producing an image. You can check in the composite view.

Mike

I seem to remember having to deal with this in the past and I'm pretty sure it's on the UE4 side. I haven't found a solution to this on the fbx export.

Mike

If you're using voronoi fracture you generally want to run it over each piece separately. Otherwise you can get some weird results.

To control what gets output to ue4 it's all about the geometry containers that you use to separate pieces before exporting to fbx. If you use the name attribute generated by the voronoi fracture you can use that to isolate each voronoi cut regardless of the plank separation.

I don't know if that makes sense but focus on the exporting stage.

Mike

Hi.
1. When you use the shelf tools to create a fluid sim it sets up the nodes needed to write out the cache. I would suggest writing out the points and then the geometry. Use the nodes created instead of the method described in the video.
2. I would suggest meshing the particles before rendering. That step can be quite time consuming and you don't want to repeat it every time.
3. On the Vertex Animation Texture ROP the target polycount parameter controls the final output.
4. I think you can use the render scheduler to track the render time and time to finish. If you have cached your mesh before exporting the vertex animation texture the process is generally quite quick.

Hey Brian,

The orientation should be correct. Have you changed your import settings in ue4 possibly?

To your second point - ue4 does provide the ability to group chunks by creating a physics object and creating different levels but as far as I know the only way to author those levels currently is through the nvidia physx lab tool.

Mike

As a quick fix you can unlock the Vertex Animation Texture node then go to /obj/alpha_test/texture_output/vertex_animation_textures1/sprite_copnet/calculate_Cd and under the Image tab set Add Plane to the first option - C, A(C:rgb A)

Hi Adrian,

It's not just you. I can't seem to get the Alpha to export either. It works if I plug the result into one of the colour channels. I'm submitting a bug to the dev team.

I don't think it'll make too much of a difference in the render but it's generally a good idea to match the resolution. Otherwise it attempts to match internally by copying and interpolating values which might not give the result you're expecting.

You need to have a matching field for both inputs. Swap your inputs into the volumemix (2nd input generally effects 1st input). After your volumeblur add a name node for the heat field and another for the temperature field. Merge those all together and use that as your mask. Right now it's only effecting density because that's all your mask has.