Physical Surfaces

Whether a round stops, ricochets, or punches through depends on the physical surface it hits. The chain is:

Mesh / Material  ──►  Physical Material (PM_*)  ──►  Surface Type  ──►  World Surfaces row
 (what you hit)        (Surface Type field)          (SurfaceType2)      (ricochet, penetration, V50…)

#1. Give your geometry a physical material

Unreal resolves the physical material of a hit in this order:

1. The Phys Material Override on the component's collision settings.
2. The Phys Material of the material on the face that was hit. Set it in the material's Details panel, or in a material instance under Physical Material (the demo's MI_Breachable_* walls do this). In a material instance, tick the checkbox next to Phys Material: without it the instance ignores its own value and uses the parent material's.
3. The engine default (surface Default).

The plugin ships one physical material per built-in surface in /MassProjectileSubsystem/Surfaces/:

Quick test: assign PM_Metal as the Phys Material Override on a cube in your level, then shoot it at a shallow angle. It ricochets. Swap to PM_Wood and it is penetrated.

#2. The World Surfaces table

Project Settings → Plugins → Mass Projectile Subsystem → World Surfaces → Surfaces

Each row describes a material's ballistic behaviour, for every projectile type. The Default row applies to surfaces without their own row.

#How a hit is resolved

1. Ricochet check. If the impact angle measured from the surface plane is below Ricochet Max Incidence Deg (scaled by the type's Ricochet Angle Scale, easier on harder surfaces), the round bounces and keeps Restitution of its speed.
2. Entry check. Otherwise the round tries to enter. It needs the normal component of its speed to exceed Min Penetration Speed and the surface's V50 ballistic limit for the actual thickness. Heavier, faster, higher-Penetration-Power rounds enter more easily; oblique hits need more speed.
3. Inside the material the round loses speed exponentially (Density Loss Per Cm ÷ Penetration Power). If the far face is past the point where it would come to rest (or past Max Penetration Depth Cm), it is buried (Stop). Otherwise it exits (Penetration Exit) and keeps flying under gravity.
4. Exit speed is the ballistic-limit residual, v × √(1 − (V50 ÷ normal speed)²) (surfaces with V50 Base Cms 0 use the drag loss instead). A round that only just beats V50 leaves almost stopped and drops to the ground; one far above V50 keeps nearly all of its speed.
5. Spent rounds. A round that neither ricochets nor enters is stopped on the face. On surfaces with Spent Drop Speed Cm above 0 (steel by default) it then falls off the face under gravity instead of vanishing.

#Fields

Physics

Ballistic Limit (V50)

Look

Breaching (Can Breach, Damage Per Hit, Breach Damage, Site Radius Cm, Hole Radius Cm, Breach * Scale): used only by the optional Projectile Holes add-on. They have no effect without it, so leave the defaults.

#Shipped values

#Using your own surfaces

If your project already uses surface slots 1–6 for other things, or you want more materials:

1. Create (or reuse) your physical materials and their Surface Type entries in Project Settings → Physics → Physical Surface.
2. In World Surfaces → Surfaces, change each row's Surface dropdown to your surface, or add rows (+) for new ones.
3. In each projectile type's Surface FX → Responses, point the rows at the same surfaces so decals and sounds match.
4. Use your physical materials on your meshes. The shipped PM_* assets become optional.

Water is special-cased by the Niagara impact system: hits on SurfaceType6 draw a splash instead of dust and sparks. If you move water to another slot, splashes fall back to the solid-surface burst.