C++ on V's personal site

Simulating 1000 flocking fish in Unreal Engine

Tue, 11 Nov 2025 00:00:00 +0000

Introduction #

Simulating the flocking behavior of birds or the schooling of fish is a classic problem in computer graphics. The Boids algorithm, created by Craig Reynolds in 1986, offers a powerful solution. It demonstrates how complex, life-like group motion can emerge from individuals following a few simple rules, without any central leader or complex choreography.

This principle offers a way to add life to game worlds. A common application is simulating a school of fish, but a significant technical challenge arises when scaling up to large numbers. The target here was to effectively simulate a school of 1000 fish, moving as one cohesive unit while still allowing for individual interaction.

TNonNullPtr: UE's bouncer for null pointers!

Sat, 08 Nov 2025 00:00:00 +0000

Introduction #

If you’ve spent any time writing gameplay code in Unreal’s C++, you know the routine. The code we all have to write.

Before you can safely use a pointer, you have to check it. This defensive habit is essential for preventing crashes, but it often leads to code that looks like this:

 1void AMyGameMode::StartRound(const AController* PlayerController)
 2{
 3	if (PlayerController)
 4	{
 5		if (PlayerController->GetPawn<AMyCharacter>())
 6		{
 7			if (PlayerController->GetPawn<AMyCharacter>()->GetMyWeaponComponent())
 8			{
 9				PlayerController->GetPawn<AMyCharacter>()->GetMyWeaponComponent()->EquipWeapon();
10			}
11		}
12	}
13}

This code is safe, perfectly fine. But it’s not clean. The core intent is buried under layers of validation. What if… we could flip this pattern on its head?

Approaches to replicate Unreal Engine's TMap

Sat, 14 Jun 2025 00:00:00 +0000

Introduction #

If you ever attempt to put a Replicated specifier on your UPROPERTY with TMap, your IDE or compiler might yell at you like this:

Why can’t TMap be replicated by Unreal? #

Unreal’s built-in replication only supports certain types that the replication system knows how to serialize. This includes basic primitives, some containers like TArray, FVector, or custom structs containing UPROPERTY fields.

Networked Deterministic Array Shuffle in Unreal Engine

Fri, 13 Jun 2025 00:00:00 +0000

Introduction #

Sometimes, you want to do a deterministic shuffle of an array for purposes like gacha mechanics, or in my case, replicating the Spin the Wheel minigame in Coral Island!

At the time this feature was developed, it hadn’t yet been made to work with multiplayer. Even though Coral Island is a co-op game, not a competitive one, Unreal Engine still adopts a server-authoritative multiplayer model.