UV Reactive decals with a spesific item

Development Programming & Scripting Blueprint
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Hi all! It’s my first time posting here and engaging with you all so I apologise if I’ve posted this in the wrong place or formatted something incorrectly. However I have a question around UE Blueprints.

I’m trying to make a spesific item (UV torch in this case) bring out decals that would be clues/codes for an escape room style project I’m working on.

My idea is there is a spesific UV torch that a player needs to use to uncover codes or codes within a room (or rooms) that allow the player to progress; standard escape room style mechanic.

I plan on having the codes be selected from a pool of different codes (I thought about using decals for these, would a decal be the best use?) that are required to open locks, or generally progress.

First question; what would be the best method for having these decals come up when lit up by the torch. Blueprinting is the obvious answer but what would be the right use of nodes? My University course didn’t really touch on blueprints at all past a basic ‘this is something you can do. Cool right?’ Sorta thing

Second question; is it even possible to have the game pull from a pool of decals and have the subsequent lock use the same code? If so, how would that be achieved?

I’ve been trying to teach myself but the documentation is confusing for someone who has basically no working understanding of the tool.

I understand these are rather big questions but I have almost no starting point and I really want to spend time learning Blueprints, the nodes/what they can do and how I can start assembling things myself with some level of self sufficiency.

Thank you all for reading :slight_smile:

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the cleanest way to do uv reveal decals:

give every clue decal material a scalar parameter, reveal, defaulting to 0 where the decal shows as ordinary dirt or nothing at all. then drive it one of two ways:

per decal: the torch does a sphere trace or cone check every tick, and any decal actor inside the beam gets its material parameter lerped to 1 through a material instance dynamic with a short timeline, so clues fade in instead of popping. this keeps it directional, only what the torch actually touches lights up.

global: one material parameter collection scalar, every clue material reads it. any torch anywhere reveals everything, no per actor references. simpler, but it is all or nothing across the level, so it fits best with a single torch.

on the decal side, check the decal is set to affect the right surface and is not being masked out by the material underneath, that is the usual reason people think the effect is broken.

this reveal mechanic is the same core loop a hidden object game uses, so if the escape room grows into searchable object scenes, the Hidden Object Game Template is a data driven hidden object game template for unreal engine 5 that handles object placement, finding and the ui side, commented end to end: Multiplayer Hidden Object Game Template | Fab