UIVSmokeCollisionComponent is a dynamic primitive component attached to the AIVSmokeVoxelVolume. It translates the abstract voxel grid data into actual physics geometry that the Unreal Engine physics system (Chaos/PhysX) can interact with.

Overview

Unlike standard static meshes, the shape of the smoke changes every frame during expansion and dissipation. This component generates collision bodies dynamically to match the current smoke shape.

How It Works: Greedy Meshing To maintain high performance, the component <strong>does not</strong> create a collision box for every single voxel. Instead, it utilizes a <strong>Binary Greedy Meshing</strong> algorithm.

It scans the voxel grid.
It identifies adjacent active voxels along the X, Y, and Z axes.
It merges them into the largest possible FKBoxElem (Box Collider).

Result: A smoke cloud containing 1,000 active voxels might only require 100-200 large physics boxes to represent its volume, significantly reducing physics simulation overhead.

Common Use Cases

1. Blocking AI Line of Sight (Default)

By default, the component is configured to Block the Visibility channel while ignoring everything else.

Behavior: AI perception systems using Line of Sight traces will be blocked by the smoke.
Player: Players and projectiles will pass through the smoke freely.

2. Physical Blockage

You can change the Collision Profile to BlockAll or Pawn to make the smoke physically solid.

Behavior: Players cannot walk through the smoke; it acts as a solid wall.
Context: Useful for magic spells ("Ice Wall") or sci-fi force fields, rather than traditional gas smoke.

Configuration

The component supports standard Unreal Engine collision settings in the Details Panel, along with specific performance tuning parameters.

Performance Throttling

Rebuilding physics geometry is an expensive CPU operation. To prevent framerate drops, the component includes a built-in throttling system that skips updates if the changes are insignificant.

Property	Description	Recommendation
Collision Enabled	Master switch. If false, no physics bodies are generated.	Disable if you only need visual smoke (e.g., background ambience).
Min Update Interval	The minimum time (in seconds) between physics rebuilds.	0.2s - 0.5s. Frequent updates (e.g., 0.0s) will cause stuttering.
Min Update Voxel Num	The minimum number of voxels that must spawn/die to trigger a rebuild.	50 - 100. Prevents rebuilding when the smoke is barely changing.

Debugging

You can visualize the optimized physics geometry to verify that the Greedy Meshing is working effectively.

Enable bDebugEnabled on the parent AIVSmokeVoxelVolume.
Enable bDebugEnabled on this UIVSmokeCollisionComponent.

Visuals:

Colored Wireframes: Represents the generated FKBoxElem bounds.
Color Variance: Each distinct box is assigned a random color to show how the voxels were merged.

‍[!NOTE] Interaction with Voxel Simulation This component does not affect the expansion of the smoke itself.

Smoke Expansion: Controlled by VoxelCollisionChannel in the Voxel Volume actor (Trace checks).

Physics/AI Blocking: Controlled by the Collision Profile of this component (Body Instance).

‍[!WARNING] Performance Cost While Greedy Meshing is efficient, regenerating physics bodies forces the physics engine to rebuild its acceleration structures. Avoid setting MinCollisionUpdateInterval to 0.0. If the smoke is purely cosmetic and does not need to block AI vision, set bCollisionEnabled = false to save significant CPU performance.