Game Destruction FX
With Houdini RBD, Axiom, and Niagara system effects.
About
In-Game VFX
Game destruction effects are a complex undertaking that requires an in-depth understanding of VDBs, Houdini solvers and simulations, and optimization techniques. By creating this environmental destruction scene, I learned how to seamlessly combine real-time FX with Houdini caches, while still being relatively light on performance cost inside game engines.
For this project, I used a kitbash pack from KitBash3D, the Axiom toolset by Theory Accelerated, and Zibra VDB.
I started by fracturing my destruction mesh. I used an iterative fracturing technique with levels (an HDA I previously created during undergrad and already had on-hand) for full control over the number of pieces I was getting. Too many pieces will slow down in-game performance and simulation, so I wanted to avoid creating future issues.
I simulated the RBD tower collapse using proxy geometry-- to save on performance cost-- caching the sim points, and then applying that point data to the final geometry. I used weak glue constraints between the pieces in order to create a 'buckling' look.
To make the smoke simulation that followed the tower collapse, I used a Pyro Source node to scatter points over the fractured pieces, rasterized the density and velocity fields, and then passed that through an Axiom solver.
Caching out the Pyro smoke took the most time of this entire project; I needed to go through many iterations for lookdev, spending about 30 hours on caching alone. The long cook time was a bit frustrating, since I have a feeling there were ways to avoid it; in the future, I'll be exploring efficient caching methods for Pyro.
Since I was already working on Pyro, I made the impact explosion.
After importing all components into Unreal Engine and syncing them with Blueprints, I integrated the Niagara effects into the simulation on a per-piece basis, attaching them with Unreal's skeleton system. My original plan was to have many effects layered on top of each other, but I found that the scene became visually overwhelming. I settled on one effect (debris with trailing smoke).
