Category Archives: UE4

Simple Random Dungeon Generating in UE4 C++

Unreal Engine Technical Writer Ian Shadden created a very complex blueprint code to generate a random dungeon (it does a lot more than just generate a dungeon!) This post just details my first time experiences working out how to create a simple C++ class to generate something similar. I’ll start by aiming to replicate the first 16 minutes of this video. This bit wasn’t too complicated in the blueprint!

If I can do that then I think I will have gained a bit more understanding of how UE4 class libraries plug together. Others have done similar but nothing like doing it yourself to understand!

Steps this blog will go through:

  1. Create project
  2. Copy Mesh content
  3. Create AWallGenerator class (derived from AActor)
  4. Override OnConstruction
  5. Load two static meshes (one for walls and one for floor)
  6. Add UInstancedStaticMeshComponents (x2) to the AWallGenerator actor
  7. Iterate and add instances to the instanced static meshes
  8. Logging messages
  9. Attach a debugger and step through code

The end result looks a bit like this:

The list above took me a few hours to work out! Luckily there are some great resources out there for UE4.

I started with a blank C++ project. File –> New Project –> C++ –> Basic Code

Where to start? I know that the thing I want to create is an actor. Something I can place “in the world” and it can do things.

File –> New C++ Class –> Actor base class

I shall create an actor class that will then generate instance static meshes. This is a common technique from other engines (where you basically just change a transform and render another copy of the same mesh).

I’ve also copied the “wall_pillar” and “floor” content from the blueprint tutorial – just so I can get it working quickly.

The blueprint example gives plenty of hints as to the way forward. I need to override the “OnConstruction” function so that I can have behaviour in the editor and at “game” time.

First problem – what is the signature of “OnConstruction”? I just looked in the base class header (Actor.h). You can right click a #include and visual studio context menu includes “Open Document”.

virtual void OnConstruction(const FTransform& Transform)

The UE4 engine has an UInstancedStaticMeshComponent (components are things that can be added to actors). The UInstancedStaticMeshComponent has a UStaticMesh and a set of Instances (basically a big list of transforms).

Classes in UE4 code base have to be correctly named or the header parser doesn’t work correctly. I’ve tried (by misnaming the odd class) and they do indeed cause some wierd compilation bugs. Anyway; this is well documented: https://docs.unrealengine.com/latest/INT/Programming/Development/CodingStandard/

In my “OnConstruction”, I iterate over two indices (for the XY plane directions), roll a random number and create an instance of a wall or a floor.

We need to physically load a mesh and bind it. The trickiest bit was working out the folder structure to load the meshes.

 UStaticMesh* floor = Cast<UStaticMesh>(StaticLoadObject(UStaticMesh::StaticClass(), NULL, TEXT("/Game/Meshes/Floor")));

Once the mesh is loaded we can create the UInstancedStaticMeshComponent.

UInstancedStaticMeshComponent* pResult = NewObject<UInstancedStaticMeshComponent>(this); 
pResult->RegisterComponent(); 
pResult->SetStaticMesh(floor); 
pResult->SetFlags(RF_Transactional); 
this->AddInstanceComponent(pResult);

I created two of these – one to hold floors and one to hold walls.

About this time I was struggling to see if the meshes were loading and whether or not I had managed to create the components correctly. Two debugging techniques spring to mind at this point – streaming data to an output log and interactive debugging. The UE_LOG macro can be used (and it is pretty straight forward to use). https://wiki.unrealengine.com/Logs,_Printing_Messages_To_Yourself_During_Runtime#Within_Editor_.28Play-In-Editor.29

Logs are great but debugging is better. https://answers.unrealengine.com/questions/253091/how-do-i-debug-c-code.html

Finally:

Loop and add instances at random:

 for (int i = 0; i != _maxX; ++i)
 {
   for (int j = 0; j != _maxY; ++j)
   {
     FTransform t(FVector(i*_tileSize, j*_tileSize, 0));
     if (FMath::RandRange(1, 10) <= 5)
     {
       pFloor->AddInstance(t);
     }
     else
     {
       pPillar->AddInstance(t);
     }
   }
 }