Procedural Vegetation System – Path Tracer, Sequencer & Transform Provider Questions

Development Cinematics & Media Virtual Production
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Hi Epic Team,

We’ve been testing the new Procedural Vegetation System to evaluate its potential for VFX workflows, and we’ve come across a few key issues/questions.

1. Path Tracer support

I wasn’t able to get vegetation animation working in the Path Tracer. By enabling r.RayTracing.Nanite.Mode 1, I was able to render the vegetation correctly in the Path Tracer, but the plants remain completely static.

-Is animated vegetation in the Path Tracer currently supported, or is this a known limitation?

-Are there any plans to integrate MegaPlants animation support into the Path Tracer?

2. Sequencer workflow

We’ve also encountered issues when using the system in Sequencer. With larger vegetation setups, Unreal tends to crash during rendering. Additionally, there doesn’t seem to be a global time parameter (or some MPC parameter) that would allow vegetation animation to be driven deterministically while scrubbing timeline.

Having a global time input would make it possible to scrub the timeline both forwards and backwards while maintaining stable and deterministic animation, which is essential for cinematic and VFX workflows.

3. Wind and Transform Provider customization

Currently, we can control the global foliage actor through the wind texture and wind speed parameters. However, we’d like much finer control over the animation—for example, adjusting branch oscillation frequency, stiffness, weight, or other motion characteristics.

Since the vegetation is implemented as Instanced Skinned Meshes driven by the Wind_TransformProvider, I was wondering:

-Is it currently possible to create a custom TransformProvider?

For example, could we implement one that doesn’t bend branches with procedural wind but instead drives an animation clip or uses a completely different deformation logic?

Overall, the system looks very promising, but these features would significantly improve its usability for high-end VFX and cinematic production.

Thanks!

Martin Galik

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Hi Martin,

Path Tracer Support

Unfortunately r.RayTracing.Nanite.Mode 1 doesn’t support animation and this mode will be deprecated and potentially removed in 6.0. Development effort has moved to Mode 2, it is expected that animation support will be added in mode 2.

The best option available today is to use non-Nanite skinned ray tracing proxies. We know that’s less than ideal, but it’s a workable interim path while Mode 2 matures.

Sequencer Workflow

On the crashes — it’s hard to pinpoint a cause without more detail. If you can share crash logs/reports, we’ll get the relevant team to investigate and, where appropriate, look at a hotfix.

In regards to overriding the time of the simulation this may be a bit more complicated as there are simulation aspects of this that are non deterministic and relies on engine delta time.

A potential prebake of the simulation is technically feasible, but we currently do not have the means of doing this. We’re discussing this internally to see whether an existing path can be adapted or whether it needs dedicated development, and we’ll follow up once we know more.

Wind and Transform Provider customization

The physical wind solver does model characteristics like stiffness, damping, moment of inertia, and per-group oscillation frequency internally. But these might not be exposed as artist-facing controls in the release build. There is active development in this area and we will get back once there is an update.

On a custom Transform Provider: yes, this should be possible. The best starting point is to use DynamicWind’s implementation as a reference.

We really appreciate the detailed feedback, and we’re glad you see the potential. This is still experimental technology — DynamicWind especially so — but PVE and Nanite vegetation as a whole are evolving rapidly, and we’re looking forward to sharing more of those advances with you soon.

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