Best way to draw camera frustum on minimap?

[FinesseAndStyle]

I’ve made a working prototype using materials and this is undoubtedly the best looking effect as it can be antialiased unlike the Canvas solution.

Here’s the code for the function that returns the 4 camera corners if you don’t already have it:

TArray<FVector2D> UGameUtility::DeprojectScreenCornersToPlane(
	APlayerController* PlayerController,
	FVector2D Offset,
	float MinimapScale,
	float ZPlane
)
{
	TArray<FVector2D> MinimapPoints;

	if (!PlayerController)
	{
		return MinimapPoints;
	}

	// Get viewport size
	FVector2D ViewportSize;
	GEngine->GameViewport->GetViewportSize(ViewportSize);
	if (ViewportSize.IsZero())
	{
		return MinimapPoints;
	}

	// Define 4 screen corners
	TArray<FVector2D> ScreenCorners = {
		FVector2D(0.f, 0.f),                // Top-left
		FVector2D(ViewportSize.X, 0.f),        // Top-right
		FVector2D(ViewportSize.X, ViewportSize.Y), // Bottom-right
		FVector2D(0.f, ViewportSize.Y),        // Bottom-left
	};

	for (const FVector2D& ScreenPos : ScreenCorners)
	{
		FVector WorldOrigin, WorldDirection;

		if (PlayerController->DeprojectScreenPositionToWorld(ScreenPos.X, ScreenPos.Y, WorldOrigin, WorldDirection))
		{
			if (!FMath::IsNearlyZero(WorldDirection.Z))
			{
				float t = (ZPlane - WorldOrigin.Z) / WorldDirection.Z;
				FVector WorldPoint = (WorldOrigin + t * WorldDirection);

				// Convert to minimap space
				float MinimapX = WorldPoint.Y * MinimapScale + Offset.X;
				float MinimapY = -WorldPoint.X * MinimapScale + Offset.Y;

				MinimapPoints.Add(FVector2D(MinimapX, MinimapY));
			}
		}
	}

	return MinimapPoints;
}

(This assumes that the minimap is static and the world is center on origin)

The material:

The update function should look like this.