Windy Cloth

Intro

Here is an R&D experiment I’ve been working on for a personal project in Unreal
The idea is fairly simple: a hybrid approach combining a Houdini cloth simulation with an Unreal shader

Step 1: Houdini Sim

You can place either a spline or a quad in the world, which then gets simulated onto selected objects using the Houdini for Unreal Engine plugin
This results in a convincing cloth behavior that naturally follows the shape of your meshes

The simulation also bakes useful data into vertex colors and UVs, which are used by the shader

Step 2: Unreal Shader

Once Unreal receives the Houdini simulation and converts it into a mesh with the appropriate material, some shader maths adds real-time wind animation on top of the pre-simulated result

This effect is driven by the baked mesh data, such as vertex distance, which helps determine wind intensity and influence

For the semi-transparency effect, I use a subtle opacity dithering, which is smoothed by TSR
That said, this can also work entirely without transparency (see the video breakdown for comparison), making it suitable for platforms that don't support TSR, such as mobile

---

While real-time performance is quite strong thanks to the use of a simple baked mesh with alpha cutout, this does not represent a production-ready system, but rather a proof of concept
It would require additional work, particularly on the HDA side, to become truly user-friendly and allow for in-depth cloth shape creation

---

Technical Breakdown

---

Houdini HDA