UE5 Global MPC Flashlight System

A lightweight, Blueprint implementation of a Flashlight system for Unreal Engine 5. Unlike standard SpotLights, this actor pushes its state (Position, Direction, Cone Angle) to a Material Parameter Collection (MPC) every frame.

This enables global shader interactions, such as:

• Revealing hidden objects inside the light cone (World Position Offset / Opacity Mask).
• Creating custom fake lighting effects on unlit materials.
• Driving gameplay mechanics based on light exposure.

🚀 Features

• C++ Powered: Core logic runs in C++ for minimal overhead compared to Blueprints.
• GPU Optimization: Pre-calculates the Cosine of the Cone Angle on the CPU to avoid expensive trigonometric functions (acos/degrees) per-pixel in the shader.
• Tick Management: Stops updating the MPC when the flashlight is turned off to save performance.
• Vector Packing: Efficiently packs data into FLinearColor vectors to minimize MPC parameter count.
  • Parameter 1: Position (XYZ) + Active State (W)
  • Parameter 2: Direction (XYZ) + Cone Cosine (W)

Logic:

// HLSL Pseudo-code equivalent
float3 ToPixel = normalize(PixelWorldPosition - LightPosition);
float DotResult = dot(ToPixel, LightDirection);

// If DotResult is greater than ConeCosine, the pixel is inside the cone.
float IsInsideCone = step(ConeCosine, DotResult);

Material Setup

DEMO