Intro, Notes & Section 3 Assets

• Welcome to our first Unreal editor section.
• You’ll learn simple level building.
• We’ll be using meshes and materials.
• C++ events accessed from Blueprint.
• Calling C++ code from Blueprint.
• And much more.

S03 Game Design Document (GDD)

The Concept, Rules and Requirements of our simple game.

Version Control 101

• The what and why of Version Control Systems
• Choosing your Version Control System (VCS)
• What files to include / exclude
• Commit = save a local snapshot
• Reset = roll-back to a previous state
• Branch, Push and Large File Support later.

Ignoring Unreal Derived Files

• Derived files can be easily rebuilt
• Other files (code, assets, level layout etc) can’t
• Ignore most derived files for version control
• Which folders to ignore in version control
• Our starting .gitignore file for Unreal.

Your First .gitignore for Unreal

• Understand Unreal creates VS projects for us
• How to re-generate VS project files
• Writing our first .gitignore file
• “Committing” our project for the first time.

Getting to Know Unreal’s Editor

• Why changes to the starter scene aren’t tracked
• Arranging a simple set of windows
• Moving around in the 3D Viewport
• Setting our start map, and committing

A Pointers Primer

• You’re about to meet pointers for the first time
• The clue is when you see a * next to a type
• Pointers are simply memory addresses
• You have to “follow” the pointer to the object
• Benefit: saves you from moving things in memory
• Disadvantage: you can lose control of data.

Unreal’s Class System

• Introducing the idea of inheritance
• Unreal’s scarily powerful class system
• Exploring using the Class Viewer
• Inheritance for “is a” relationships
• Components for “has a” relationships.

Runtime Messages for Feedback

• Using UE_LOG to print to the Output Console
• Printing to the game screen

Useful Links

• Epic Wiki - Logs, Printing Messages to Yourself During Runtime

Accessing Object Names

• Use GetOwner() to find the component’s owner
• *AActor is a pointer to an actor, a new concept
• Use -> to access methods through pointers
• Use GetName() to find the object’s name
• Use %s as a format operator for strings
• Use * to “dereference” pointers.

Getting Transforms in C++

• Introducing FVector
• Mixing . and -> to access methods
• Using multiple format operators
• Finishing our PositionReport component.

Moving Objects With C++

• A little more about the editor & temporary actors
• How to eject yourself from the possessed pawn
• Snapping objects to the floor (END key)
• Using the FRotator struct to represent rotation
• Use SetActorRotation() to rotate objects.

Laying Out Geometry

• A brief intro of BSP “vs” Static Meshes
• Use Q, W, E keys to translate, rotate, scale
• Make good use of grid snapping and quad view
• Hold ALT + drag translate to duplicate an object
• Hold L and double-click for temporary work Light
• This is fiddly, try letting go of L and trying again.

Applying Materials

• A material is comprised of texture(s) and shader(s)
• Textures are image files, shaders are GPU code
• Unreal ships with some impressive examples
• Unreal has powerful material editing tools
• Applying materials to our room interior.

Macros Starting with UPROPERTY

• A macro is a programmed cut-and-paste
• This happens before the code is compiled
• Can unlock powerful functionality
• We don’t get code complete as standard
• Can also create really weird build errors
• Expose ATriggerVolume* to the Details window

Using Trigger Volumes

• A trigger volume is a very versatile tool
• A 3D volume that detects things entering / leaving
• We’re going to use one as a pressure plate
• How we’re going to specify what can open doors
• Use IsOverlappingActor() on ATriggerVolume
• Polling vs using events.

Unreal’s PlayerController

• We’ve used GetOwner() to search “bottom-up”
• Now let’s use GetWorld() to search “top-down”
• Game Mode specifies the Default Pawn Class
• The Default Pawn is your “body”, is transient
• The Player Controller is your “mind”, persist
• PlayerController class has GetPawn()

Using Collision Volumes

• Collisions volumes are also known as colliders
• These tell the physics engine what hits what
• A trigger volume just triggers code
• A collider actually has physics simulated
• Exploring how to add collision volumes
• Prevent players from passing through the door!

Using GetTimeSeconds()

• Using GetWord()->GetTimeSeconds()
• Making our game highly “play tunable”
• Re-factoring our code for simplicity
• Using a spotlight to provide “affordance”
• Play-testing to ensure the game is annoying!

Grabbing System Overview

• We want to be able to lift the chair next
• We’ll add a Grabber.cpp component to the player
• The player is a temporary actor, appears on play
• The Game Mode sets which Default Pawn to use
• Create Default Pawn & Game Mode Blueprints
• Specify our modified Default Pawn.

Modifying the Default Pawn Actor

• Why Blueprint is helpful in this case
• How to make a Blueprint from the Default Pawn
• Note this Blueprint class inherits, an “is a” relation
• A Blueprint is like a template
• You make an “instance” in the scene
• Explore “instantiating” from Blueprint & modifying.

Inherit Game Mode Blueprint

• “Hard coding” means assets written into code
• The DefaultPawn_BP is an asset
• We want to be able to track changes to its name
• It is convenient to use Blueprint for this purpose
• Extending our C++ Game Mode with Blueprint
• Selecting the new DefaultPawn_BP

Getting Player Viewpoint

• Know where the player is looking
• Out-parameters can be confusing
• A way of marking-up out parameters
• Continuously logging player viewpoint.

Using DrawDebugLine

• How to add vectors
• Calculating our line trace end point
• Using debug functions for visualisation in Unreal
• Use DrawDebugLine() to visualise the vectors.

Line Tracing AKA Ray-Casting

• Line tracing (AKA ray casting) is a very useful tool
• Imagine we shine a virtual laser into the world
• We can use different view modes to visualise
• Simulating physics sets the object channel.

LineTraceSingleByObjectType()

• Meet references for the first time
• LineTraceSingle may be deprecated
• Build params inc. FCollisionQueryParams

REFERENCES & POINTERS

• How references and pointers compare
• How to perform common operations in both
• What the & and * symbols means in context
• Challenge: Repoint and Rewrite
• When to use references over pointers?

Resetting Your Unreal Project

• What to do if your Unreal solution keeps crashing
• How to delete all temporary files
• The order in which to reset things

Using FindComponentByClass()

• What FindComponentByClass() does
• How to use it to find attached components
• Introducing angle brackets <> for generics
• Use nullptr to initialise your pointers
• Log a useful error if the component isn’t attached.

Introducing Input Binding

• Settings > Project Settings > Engine > Input
• Action mappings are used for on / off actions
• Axis mappings are used for analog values
• You can give players a way or re-mapping
• Many keys can bind to one action
• How to call a function on a key press or release

Accessors & Memory Layout

• How the arrow, dot and :: accessors work
• Introducing virtual memory
• Introducing permanent storage, stack & heap
• Heap is also known as free store
• How accessor operators relate to memory
• Bind another input action

Reducing Code in “Hot Loops”

• A “hot loop” is code that get called often
• TickComponent is a good example, every frame
• Beware of code that you know will be called a lot
• Make it clear what happens every tick
• Refactor our code for speed...
• ...and make it ready for for the physics handle.

Using Physics Handles

• Unreal provides a Physics Handle that’s ideal here
• The Physics Handle component docs are scant*
• Find an example of its use in the engine
• Get the physics handle working.

Useful Links

• Unreal Engine API Reference - UPhysicsHandleComponent

Refactoring Rules

• Using multiple getters for multiple return values
• Less lines of clear code is better (143 at start)
• Naming is really important, take the time
• Comment the “why”, don’t assume it’s obvious
• The “what” should be obvious...
• … but it can be helpful to add clarification

Introducing Unreal’s TArray

• A TArray is Unreal’s go-to container class
• Use to contain many elements of same type
• We’ll use to contain all actors on pressure plate
• Give our Default Pawn an eye-height and mass
• Making our pressure-plate based on total mass.

Iterating over TArray with for

• Using auto& as an auto reference type
• Automatically iterating over a TArray
• Pattern: for (const auto* Iterator : Array)
• How to find an actor’s mass
• Tweaking and testing our mass values.

Debugging Game Issues

• Are you using source control? If not start now
• You can “binary search” commits quite fast
• For example 1024 commits takes max 10 tries!
• Think “what changed” and “possible side-effects”
• Remember you can eject with F8 during play.

Managing Texture Tiling

• You may want to re-size objects (e.g. panels)
• Doing so will stretch the texture
• You can re-scale a few ways
• One way is in the material blueprint
• UV mapping because we ran out of letters!
• Using the TexCoord node in the material editor.

Pointer Protection Process

• Horrible crashes when we follow a nullptr
• We must always check pointers before use
• When declaring always initialise to nullptr
• Look for * in your .h files to help find pointers
• Also check before every use and handle nullptr
• Sometimes we may chose not to, e.g. Owner.

Exposing Events to Blueprint

• Sometimes Blueprint’s the better choice
• For example defining our door swing as a curve
• We can create an event called OnOpenRequest
• Using UPROPERTY (BlueprintAssignable)

Using Blueprint Timeline

• The Timeline node in Blueprint has a curve editor
• This is ideal for defining our door movement
• How to use Timeline curves in Blueprint
• Setting rotation from a Timeline.

Everything in its Place

• Using Blueprint has superseded some code
• It’s important there’s only 1 place per parameter
• Creating a 2nd event: OnClose

Using Variables in Blueprint

• Not all doors have the same absolute rotation
• We want to store the door’s rotation at the start
• … then use this value to make a relative rotation
• We can use Blueprint variables for this
• Making doors that face any direction work.

SFX & Audio Clips

• We’re going to trigger a simple sound in Blueprint
• Later in the course we’ll use C++ too
• However we’ll always reference our assets via BP
• How to trigger a 3D sound.

Section 3 Wrap-Up

• Congratulations on another complete section
• You’ve learnt so much, look at the lecture titles
• Please carry-on a little on your own and share
• Attached are useful resources
• Start the next section as soon as you’re finished.