Procedural Content Generation with Unity

Pier Luca Lanzi e Michele Pirovano – Codemotion Milan November 2015
Procedural Content Generation with Unity

what’s the basic principle?

f(x) = sin(x)
float y = 0f;
for (float x = 0f; x<6.28f; x+=.01f) {
y = Mathf.Sin(x);
}

What the ingredients?
domain knowledge
structured randomness
multi-layering
filters, limits & restrictions
specialized algorithms
artificial intelligence
gameplay integration

Outline
procedural geometry
colors & music

Procedural Geometry

/// specify vertices
Vector3[] vertices = new Vector3[4];
vertices[0] = new Vector3(0.0f, 0.0f, 0.0f);
vertices[1] = new Vector3(0.0f, 0.0f, m_Length);
vertices[2] = new Vector3(m_Width, 0.0f, m_Length);
vertices[3] = new Vector3(m_Width, 0.0f, 0.0f);
/// specify 2 triangles
int[] indices = new int[6];
/// triangle 1
indices[0] = 0;
indices[1] = 1;
indices[2] = 2;
/// triangle 2
indices[3] = 0;
indices[4] = 2;
indices[5] = 3;
/// create the mesh
Mesh mesh = new Mesh();
mesh.vertices = vertices;
mesh.triangles = indices;
mesh.RecalculateBounds();

/// create the normals
Vector3[] normals = new Vector3[4];
normals[0] = Vector3.up;
mesh.normals = normals;
/// create the UV for the full texture
Vector2[] uv = new Vector2[4];
uv[0] = new Vector2(0.0f, 0.0f);
mesh.uv = uv;
/// create the UV for half texture
Vector2[] uv = new Vector2[4];
mesh.uv = uv;

public class MeshBuilder
{
public List<Vector3> Vertices;
public List<Vector3> Normals;
public List<Vector2> UVs;
public void AddTriangle(int i0, int i1, int i2);
public Mesh CreateMesh()
}
MeshBuilder meshBuilder = new MeshBuilder();
//Set up the vertices and triangles:
meshBuilder.Vertices.Add(new Vector3(0.0f, 0.0f, 0.0f));
meshBuilder.UVs.Add(new Vector2(0.0f, 0.0f));
meshBuilder.Normals.Add(Vector3.up);
...
meshBuilder.AddTriangle(0, 1, 2);
meshBuilder.AddTriangle(0, 2, 3);
...

MeshBuilder meshBuilder = new MeshBuilder();
for (int i = 0; i < m_SegmentCount; i++)
{
float z = m_Length * i;
for (int j = 0; j < m_SegmentCount; j++)
{
float x = m_Width * j;
Vector3 offset =
new Vector3(x, Random.Range(0.0f, m_Height), z);
BuildQuad(meshBuilder, offset);
}
}

12

Ingredients #1 & #2
Domain Knowledge & Artificial Intelligence
•  Domain Knowledge
§ To generate something you need to know it
§ PCG typically aims at building an artificial level
designer, usually needs domain knowledge
about level design
•  Artificial Intelligence
§ Need algorithms that can work on complex
knowledge and generate plausible content
§ Search-based methods, L-systems, evolutionary
computation, fractals, cellular automata,
agent-based methods, planning, etc.
13

14
ESEMPIO CON LA CAVE?
ESEMPIO DI DUNGEON?

ingredient #3
structured randomness
things look like they have been randomly
generated but it is not completely at random!

f(x) = sin(x)

they both look like “noise”
but one of them feels like it has structure…
it is structured randomness

ingredient #4
multi-layering
typically more layers of procedural
content generation are applied in sequence

•  Warzone 2100
§ Heights & Cliffs
§ Roads
§ Textures
§ Player Bases
§ Local Features
•  Civilization 4
§ Fractal Heightfield
§ Plate Tectonics
§ Tile Types
§ Rivers and Lakes
§ Map Bonuses

ingredient #5
Filters, Limits & Restrictions
“In Civ3 I would say we even shipped with a sub-standard resource
placement algorithm where all the iron could be concentrated in just
a few small locations on the map, and for one player there may be
literally no way for them to build swordsmen.” – Soren Johnson
"With Civ4 we instituted randomness with limitations. There
always has to be a minimum distance between each element of
iron, or each element of horses, and that completely solved the
problem.” – Soren Johnson

ingredient #6
specialized algorithms
placing special items, requires special tricks
this tricks must be encoded in the PCG

1.  Connect all bases, the resources,
pick three random points and
connect them
2.  Apply a customize A* heuristic
and reuse roads!
3.  Customize A* heuristic with
randomize cost of non-road
grid cells.

ingredient #7
gameplay integration
Is it fun to play? Is the progression adequate?

is this all there is?

PCG
Is it done online?
Or offline?
Is it necessary content?
Or optional?
Do you use random
seeds or parameter
vectors?
Is it stochastic?
Or deterministic?
Generate and test?
Constructive?

we can do it, so can you!

Pier Luca Lanzi e Michele Pirovano – Codemotion Milan November 2015http://trackgen.pierlucalanzi.net

http://www.youtube.com/watch?v=uIUYWzdMXog

Pier Luca Lanzi e Michele Pirovano – Codemotion Milan November 2015http://www.michelepirovano.com/portfolio_swordgenerator.php

http://www.polimigamecollective.org
http://www.facebook.com/polimigamecollective
http://www.youtube.com/PierLucaLanzi

Procedural Content Generation with Unity

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