## Abstract

This supplementary material provides video demonstrations of the physical simulation and rendering ability proposed in the paper.

## 1. Main Simulation Results

Our qualitative showcase of new, scene-level heterogeneous simulations produced using our framework. Each row demonstrates a unique coupling of different asset types and physics solvers.

Row 1: Fluid (SPH) on Virtual Mesh. A virtual fluid (SPH) is poured into an imported virtual mesh (bowl), interacting with both the bowl and the static 3DGS scene (garden table).
Row 2: Fluid (SPH) on GS Soft Body (MPM). A high-viscosity fluid (SPH) is coupled with a captured 3DGS soft body (MPM donut), demonstrating complex multi-solver, two-way interaction on a plate.
Row 3: Articulated Rigid Body Manipulation. A kinematically-driven robotic arm (articulated-body solver) manipulates a virtual rigid body (cube) on a table.
Row 4: Cloth (PBD) on Captured Statue. A virtual cloth (PBD solver) realistically drapes and slides over the complex, non-convex geometry of a captured 3DGS statue.
Row 5: Rigid-Body Collision in 3DGS Container. Multiple virtual rigid bodies (fruits) interact with each other and with the complex geometry of an imported 3DGS asset (the basket).

These scenarios are, by design, unattainable by prior "siloed" methods.

## 2. Additional Qualitative Results

Further demonstrations illustrating the versatility of our framework in handling diverse material properties and coupling scenarios.

(a) Heterogeneous Materials

(b) Granular-Soft Interaction

(c) Articulated Manipulation

(d) Viscous Fluid Coupling

## 3. Comparisons with Previous Work

Note on Comparison Scope: Strictly speaking, a direct comparison is challenging because our framework is the first to support a holistic workflow involving 3DGS + Imported Meshes + External Particles. Prior works (e.g., PhysGaussian, DecoupledGaussian) operate in a "siloed" manner, unable to support imported mesh interactions or external particle coupling.
Therefore, for the following comparisons, we intentionally downgraded our method to a "3DGS-only" setting to match their scope. Even under this restricted setting, our method demonstrates superior capabilities in handling complex scene surfaces and heterogeneous physical property coupling.

### Comparison A: vs. PhysGaussian

PhysGaussian
Ours (Downgraded)

Analysis: While PhysGaussian only supports ideal plane as simulation boundary, our method provides more stable behavior on complex surfaces.

### Comparison B: vs. DecoupledGaussian

DecoupledGaussian
Ours (Downgraded)

Analysis: Comparison of physical property coupling. Our method enables diverse heterogeneous material assignments, such as coupling liquid and soft body dynamics within a single object. Note: To ensure a fair comparison, we omit complex boundary conditions in this example.