Materials — Dynamic Floor Plugin

Materials

This page explains how the material system works in the Dynamic Floor Plugin and how to set up your own material assignments.

How materials work

The plugin uses an integer ID system for materials. Each floor polygon stores a MaterialId (an int32 value) rather than a direct reference to a UMaterialInterface.

Why integer IDs?

From the official documentation:

“Materials in this Plugin are assigned over IDs — The thought behind this is, that maybe later users are able to like upload own materials/textures you name it. Then it must be a mechanism to get the surface data from anywhere where you store it right. So imagine a huge Sims game. Every user contributing textures or something. You get like millions of surfaces. So an ID-Surface data relation will be essential.”

This design allows materials to be stored in an external system (a database, a web service, user-generated content) and resolved at runtime — not hard-coded as asset references.

The SimpleMaterialManager

The plugin includes a SimpleMaterialManager Blueprint. Its job is to map MaterialId integers to actual UMaterialInterface objects at runtime.

The official documentation notes:

“So I created a ‘SimpleMaterialManager’ to be able to dynamically assign a lot of materials over IDs. That we have to create too. […] So any BP you make just needs to implement an interface and can be used here.”

This means you can replace SimpleMaterialManager entirely with your own implementation as long as it implements the expected interface.

Assigning a material during placement

When spawning the placement tool via your HUD, you pass the FloorMaterial (integer ID) as a parameter:

PlaceFloor(FloorType, FloorMaterial)

This ID is carried through the entire pipeline:

PlaceFloor(FloorType=Default, FloorMaterial=3)
  → FFloorInputEvent.MaterialId = 3
    → UPolygonDatabase.AddPolygon(..., MaterialId=3, ...)
      → FFloorPolygon.MaterialId = 3
        → BP_FloorPolygonRenderer groups polygons by MaterialId
          → SimpleMaterialManager resolves MaterialId=3 → UMaterialInterface
            → assigned to the corresponding ProceduralMesh section

Per-polygon material data (`FFloorPolygon`)

Every polygon in the database includes:

Field	Type	Description
`MaterialId`	`int32`	The integer material identifier
`FloorType`	`EFloorType`	The logical layer type

Floor Types and material rendering

EFloorType provides an additional layer of separation on top of MaterialId:

Value	Typical use
`Default`	Visible floor surfaces
`Border`	Wall boundary polygons (may be invisible or use a separate material)
`Invisible`	Logical-only polygons — no visible mesh

The renderer (BP_FloorPolygonRenderer) can group and filter by both MaterialId and FloorType.

Use UPolygonDatabase.GetPolygonsInBoxFiltered(Box, MaterialId, FloorType, HeightLevel) to query polygons by specific material and type.

How the renderer uses material IDs

BP_FloorPolygonRenderer maintains one ProceduralMesh section per MaterialId. When OnAllPolygonsTransferred fires:

It collects all polygons that have received changes (marked dirty by OnPolygonAdded / OnPolygonRemoved).
For each dirty MaterialId, it regenerates the full mesh section.
It calls SimpleMaterialManager (or your equivalent) to resolve the MaterialId to a UMaterialInterface.
The material is applied to the mesh section.

Querying polygons by material

Get Polygon Database → GetPolygonsInBoxFiltered(
    Box = your area,
    MaterialIdFilter = 3,
    FloorTypeFilter = Default,
    HeightLevel = 0.0
)

Returns all floor polygons in the specified area with the given material and type.