This document outlines a project pitch for using Answer Set Programming (ASP) for procedural content generation. ASP is a declarative problem solving approach that describes a problem's rules rather than how to solve it. The solutions are represented as sets of answers. The presenter aims to research procedural content generation techniques, apply ASP to map/planet generation, and use ASP to procedurally generate game maps. Goals include visualizing maps and experimenting with directly creating levels when rules fire or enabling real-time content generation.

1. Innovation and Professional Development
Project Pitch
Answer Set Programming
for Procedural Content Generation
by Andrea Tucci
@andreatux

2. Outline
➔ Procedural Content Generation
➔ Answer Set Programming
◆ the HEX programs
➔ Goals

3. Procedural Content Generation
➔ Procedural Content Generation (PCG) is an “algorithmical creation of game
content with limited or indirect user input”[1]
◆ levels, maps, music, quests, story …
➔ Software that, given some “rules”, is able to create new game elements
➔ Offers new ways of playing the game; new player experiences
[1] J.Togelius, E.Kastbjerg, D.Schedl, G. N. Yannakakis: What is Procedural Content Generation?Mario on the borderline (2011)

4. Procedural Content Generation
➔ Why?
◆ new content
◆ efficency
◆ no designers…
● ...really? I like to think of PCG as a “tool” for designers
◆ automated procedure
◆ great for small teams
◆ experiments
◆ player-based content (data mining)

5. Procedural Content Generation
➔ Examples

6. Procedural Content Generation
➔ Planet Generator:
http://experilous.com/1/planet-generator/2014-09-28/version-
1

7. Answer Set Programming
➔ Declarative problem solving approach
◆ roots in logic programming
➔ Write the description of the problem rather than how to solve it
◆ set of rules
◆ a rule can that is evaluated to be true, will fire
➔ Solution(s) to the problem, if exists, will be represented as sets of
answer

8. Answer Set Programming
Classic example: Sudoku
➔ Encode a cell with the predicate cell(X,Y,N)
◆ X,Y are the coordinates of the cell
◆ N is the number contained

9. Answer Set Programming
➔ Make a “guess” of what number can be in a cell
◆ cell(X,Y,1) v cell(X,Y,2) v cell (X,Y,3) v … v cell(X,Y,9) :- row(X), column(Y)
➔ Discard unwanted combinations
◆ Do not put the same number, given a row
● :- cell(X,Y,N), cell (X,Y1,N), Y1!=Y
◆ Do not put the same number, given a column
● :- cell(X,Y,N), cell(X1,Y,N), X!=X1
◆ Do not put the same number in a block
● :- cell(X,Y,N), cell(X1,Y1,N), sameBlock(X,Y,X1,Y1)
➔ Answer in this form: {cell(0,0,3), cell(0,1,8) … }

10. The Hex Programs
➔ Support external knowledge
◆ it is possible to make reasoning outside the logic program
➔ Call a c++ function
◆ &firstbelow[P,objs](O)
● in AngryHex, ASP-based Angry Birds bot, returns the object O
which is directly below P, given the objects objs
➔ ACTHEX extension
◆ rules that, when fired, call an external action that is able to change the
environment

11. Goals and Objectives
➔ Research on Procedural Content Generation algorithms and techniques
◆ focusing on map/planet generation
➔ Research on Answer Set Programming application on PCG
◆ how can ASP be applied to PCG?
◆ how HEX and ACTHEX extension can be useful for this goal?
➔ Use ASP to procedurally generate game maps
◆ decouple logic from actions
◆ represent levels in structured files
➔ Map Visualization
➔ Experiments
◆ directly create levels when rules fire
◆ real-time content generation(?)

12. Goals - rough idea

13. Readings and References.. so far
● J.Togelius, E.Kastbjerg, D.Schedl, G. N. Yannakakis: What is Procedural Content Generation?
Mario on the borderline (2011)
● Shaker, Noor and Togelius, Julian and Nelson, Mark J. : Procedural Content Generation in
Games: A Textbook and an Overview of Current Research
● Procedural Content Generation Wiki: http://pcg.wikidot.com/
● T.Eiter,G.Ianni and T.Krennwallner: Answer Set Programming: A Primer
● F.Calimeri, M. Fink, S. Germano, A. Humenberger, G. Ianni, C. Redl, D. Stepanova, A. Tucci :
AngryHEX: an Artificial Player for Angry Birds Based on Declarative Knowledge Bases

14. Games Reference
From the top left pic, from left to right:
● Elite, Acornsoft 1984
● Rescue on Fractalus, Activision 1984
● Minecraft, Mojang 2009
● Diablo 2, Blizzard 2000
● The Binding of Isaac, E.McMillen, F. Himsl 2011
● No Men’s Sky, Hello Games 2015 (expected)
I

15. Questions?