UE3 to UE4 Transition Guide

From Epic Wiki


Here you can find a list of procedure and terminology differences between UDK and Unreal Engine 4 gathered by the community. Keep in mind that some of those may be subject to change in time with newer UE4 releases.

General Editor & Terminology

Scene Scale(Units)

UE3: 1uu == 2cm

UE4: 1uu == 1cm

UE3: World size = 10.48km x 10.48km

UE4: World size = 20km x 20km

Assets and Packages

UE3: Packages are used to store a collection of assets. Package format .upk - Map format .udk

UE4: Each asset is stored in its own file. Maps are still packages as they need to store a collection of assets. Asset format .uasset - Map format .umap

Mesh/Skeletal Mesh & Animation Import Formats

UE3: .psk & .psa / .FBX
Collision namingĀ : MyMesh, UCX_MyCollision

UE4: .FBX(same Export procedure - Mesh and Skeleton split into 2 separate asset after import)
Collision namingĀ : MyMesh, UCX_MyMesh_## (_## is a number in case you have several UCX in there)

Disabling Decal Render on Skeletal/Static Meshes:

UE3: Go to decal properties (F4) and disable bProjectOn.

UE4: Select your Mesh in Viewport.

  1. In details panel search for Decal
  2. Uncheck Receives Decals.

Spline Loft Actor

UE3: Created by dragging and dropping from Actor Classes tab. Continue drawing a path by holding Alt and dragging the icon.

UE4: It appears in the landscape editor as Spline Tools when you create a landscape. Click Manage > Edit Splines > Ctrl+click to place one then continue drawing by placing control points with Ctrl+click, finally hit Apply Settings button in the landscape editor.

Collision Terminology

UE3: Touch and Block

UE4: Overlap and Block


Navigation, Maya Style

considering UDK <=> UE3

UE3: L + left or right mouse button

UE4: Alt + left or right mouse button

Kismet > Blueprints(Matinee included)

Creating a Matinee

UE3: Open Kismet, right-click the canvas and select New Matinee.

UE4: Search for MatineeActor in Modes tab > All Classes, and drag it into your level.

Attaching Actors to Specific Groups inside Matinee

UE3: Create a variable for the object inside Kismet and attach it to Matinee.

UE4: Select the object in the map, open up Matinee, right click on the group you want to attach > Actors > Add(or replace) selected actors.

Sequential or random activation of multiple outputs

UDK: Switch node in Kismet.

UE4: MultiGate node in Blueprints.


Adding a SkyLight

UE3= Actor Classes - Lights - Sky Lights

UE4= Modes Tab > Lights > Sky Light

Adding a dynamic light

UE3= Actor Classes > Lights > AnyLightMoveable.

UE4= Add a normal light into your level - in the settings you can find Transform > Mobility > Moveable.

Lightmaps and photons

UE3= Emissive material enabled in object in the level, photons will fire from any shape: material based.

UE4= For dynamic emissive lighting, needs to be enabled in advanced material properties(for LPV.) For static emissive lighting, enable Use Emissive for Static Lighting in the object's details panel.


Subsurface Scattering

UE3: Achieved with transmission mask

UE4: Achieved with SubsurfaceColor - choose MLM_Subsurface in the Lighting Mode

Adjusting a Particle's Color in Cascade

UE3: By multiplying the texture with a Vertex Color node in the material.

UE4: By multiplying the texture with a Particle Color node in the material.

Soft Edge for Particles and Translucent Materials

UE3: Attach the opacity mask to Alpha input of DepthBiasedAlpha and set Bias scale for fade distance.

UE4: Attach the opacity mask to Opacity input of DepthFade and set Fade Distance.

Colored Speculars

UE3: By pluging the colored specular texture to Specular input.

UE4: By giving metallic value(Constant - 1) to the material


Spawning Actors


var Actor MyActor;

MyActor = Spawn(class'ActorToSpawn',Location,Rotation);


FActorSpawnParameters SpawnInfo;
SpawnInfo.bNoCollisionFail = true;

ASoulHunterWeapon* NewWeapon = GetWorld()->SpawnActor<ASoulHunterWeapon>(Weapon, SpawnInfo);

There are several versions of Spawn one with and without templates.

If you want to use location and rotation make sure you make variables that are const.

const FVector* SLocation;
const FRotator* SRotation;

GetWorld()->SpawnActor<ASoulHunterWeapon>(Weapon, SLocation, SRotation, SpawnInfo);

Spawning Objects

This can be used to create instances (or more accurately, pointers to instances of) classes derived from Object.


var MyObject MyObjectRef;

MyObject = new class'MyObject';


In YourClass.h:

MyObject *MyObjectRef;

In YourClass.cpp:

MyObjectRef = NewObject<UMyObject>(this, UMyObject::StaticClass());

Also see Documentation - Objects for a detailed description.