Blueprints in Unreal Engine 4 can be both loved and hated. To reduce hate for blueprints, the presenter recommends using events over ticks, components to generate events, enums and switches instead of branches, multiple graphs for organization, functions, macros, and following good programming practices. While blueprints may seem like programming, they are advantageous for certain tasks like interfacing with shaders. Following design best practices can make blueprints more readable and maintainable. Alternatives to blueprints include UnrealEnginePython, Unreal.js, and SkookumScript. An indie game called Downward successfully used blueprints.

1. Unreal Engine 4
Blueprints:
Hate and Love
Roberto De Ioris
@unbit
http://aiv01.it
http://github.com/20tab
Codemotion Rome 2017

2. Disclaimer
https://github.com/20tab/UnrealEnginePython

3. Blueprints ?

4. Blueprints …

5. Blueprints :)

6. Blueprints :|

7. Blueprints :(

8. !!!

9. How to reduce Hate ?

10. First Rule: Use Events
Tick is an antipattern in Unreal Engine

11. Why Events ?
• “Code” organization
• Networking friendly
• Time management for free
• Triggerable by animations too
• Easy to explain to non programmers: cause->effect

12. Come on, we need Ticks…
Use Components

13. MoveForwardComponent

14. Generating events from
components: Event Dispatchers

15. Subscribing to Events

16. NO-if/branch
https://cirillocompany.de/pages/anti-if-campaign

17. Good Branch (single path)

18. Evil Branch

19. Anti-IF Weapons in
Unreal Engine 4
• ENum’s
• Maps (UE4 >= 4.15)
• Switch statement (???)
• Events !

20. ENum + Switch Example

21. Organization:
Multiple Graphs

22. Comments
Consider them as “visual grouping” too

23. Functions

24. Functions VS Events
• Events can be replicated (networking)
• Events can be interrupted (delay, timelines)
• Events cannot return values
• Events have no local variables

25. Macros
• Raw way to re-organize code in function-like blocks
but without functions limits

26. Blueprint Utility Functions
For Programmers: Static functions ;)

27. Re-routing nodes

28. Auto-Collapsing

29. … collapsed to function

30. Debugging
• Real time graph traversing
• watch values
• clients/server attaching
• break points
• stepping

31. A Debugging session

32. Interfaces
• Decoupling
• Decoupling
• Decoupling
• Decoupling
• …

33. IDamageable

34. Hey !
• Functions
• Interfaces
• Debugging
• Variables
• Conditionals
• Type Casting
• …

35. “I Fear Writing Blueprints IS
programming…”

36. Blueprints VS C++
• The UE4 C++ API is not fully exposed
• Using blueprints for shaders (materials) is
extremely advantageous
• Interfacing with C/C++ is a must for libraries
• Good designed Blueprints are easy to read even
for non programmers
• Blueprints are sometimes too much “silent” on error

37. The Obvious Truth ?
Honour the “good programming/design rules” and
your blueprints will be more like coding instead of
spaghetti

38. Alternatives
• UnrealEnginePython
• Unreal.js
• SkookumScript

39. An Indie Success Story
Downward by Caracal Games
http://store.steampowered.com/app/506900/

40. Thanks
• http://aiv01.it
• info@20tab.com
• https://github.com/20tab/UnrealEnginePython
• https://github.com/ncsoft/Unreal.js/
• http://skookumscript.com/