Prerequisites

• Java 17 or newer (pre-configured to Java 21)
• Make sure your PATH and JAVA_HOME env. variables point to it
• Windows / Mac / Linux
• GIT
• Usable from some shell / Command Prompt
• (Recommended) IntelliJ IDEA
• Community edition suffices
• As a student you can get Ultimate by just entering your student number

Procedural Content Generation for Computer Games

Labs 1 - Minecraft

About Minecraft

• Created by Markus Persson (Notch) in 2009 (released 2011)
• Later bought by Microsoft, 180 million copies sold (!)
• Life in an editable voxel world

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Survival mode

• Start with nothing and try to change the world to your liking ☺
• World is 1m x 1m x 1m blocks

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• The main mode Minecraft is played

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Technical info

• Minecraft was originally written in Java
• Currently has two versions (similar except for small details):
• Minecraft Java edition – has more community plugins
• Minecraft for Windows 10 (formerly Bedrock edition) – cross play on Windows, Mobile, Xbox, etc.
• Tested by using Java 21

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• Official client is a paid game, running a server is free
• NOTE: Owning the game is not a requirement to pass the homework
• But, if you want, you can buy Minecraft at

https://www.minecraft.net/en-us/store/minecraft-java-edition

Terrain in Minecraft

• The height coordinate is Y

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• The height of the world is 384 blocks (increased from 256 in 1.18)
• Separated into chunks of 16 x 16 that are generated dynamically when player first comes close
• From layer 60 it contains indestructible bedrock (but caves can go until -64)
• Layer 62 is the sea-level
• Layer 127 is the cloud layer
• Ores spawn at different layers, e.g. diamond ore is very deep

The challenges

• Terrain is volumetric, so just a heightmap is not good
• The world is (practically) infinite

The Homework

• Write a procedural terrain generation for Minecraft!

The Repository

Start with minecraft-terrain from the repo, which contains a Gradle buildsystem to instatiate server with a custom terrain generation plugin.

Using IntelliJ IDEA as IDE is highly recommended

Two tasks:

• runServer - runs a Minecraft server with plugin (useless if you don’t own MC)
• Runs indefinitely - type “stop” to stop it
• generateMap – just generates a map into a PNG file (build/render/map.png)

The first run may take a few minutes to complete. Java >=17 required.

After the first run and error, edit server/eula.txt – set it to true.

Put your changes into MCWorldGenerationPluginKotlin/src/main/kotlin/cz/cuni/gamedev/nail123/mcworldgeneration/CustomChunkGeneratorKotlin.kt

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Kotlin / Java options

• Using Kotlin is optional
• For Java, switch the constant in: cz/cuni/gamedev/nail123/mcworldgeneration/PluginLanguage.kt
• And put changes in: cz/cuni/gamedev/nail123/mcworldgeneration/CustomChunkGeneratorJava.java

Testing it out

• Run gradlew build
• Run gradlew generateMap (will be in build/render)
• Run gradlew runServer (and then type “stop”)

WARNING: First run will fail, you need to accept eula.txt in server/.

• Optional: Switch the default language to Java
• Alter the modifying generator – add a new height interval, that maps to any material (e.g. pumpkins)
• For the map generator to recognize it, map it to some color in cz/cuni/gamedev/nail123/mcworldgeneration/visualizer/Material2Hue.kt
• Generate map with your new material

Getting Minecraft

• If you want to buy Minecraft (OPTIONAL), get it at the official page https://www.minecraft.net/en-us/store/minecraft-java-edition

Criteria

• You must do at least one of the following tasks:
• Separate the world into biomes
• Generate caves for exploration

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• Perlin and Simplex noise generators are available to you
• Generally try to achieve results you would be happy to put into your own game
• So try out some things, e.g. different noises, domain warping, …
• Also see lecture slides for more info about methods

Option 1 - Biomes

• Recommended if you don’t own Minecraft
• Have at least three biomes, e.g. mountains, grassland, desert, sea…
• Use noise to generate the biomes
• Unless using a Whittaker diagram, any biomes should be allowed to touch
• Each biome must have different parameters for terrain generation (e.g. flat deserts, tall mountains, …)
• Also, ensure the transitions are smooth (interpolate)
• Optionally use a (any) Whittaker diagram - for points

Option 1 – Biomes - Challenges

• How to use noise to part an infinite plane into biomes?
• How to interpolate surroundings?
• Linear interpolation is fine, but you may also use smoothstep

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Option 1 – Hints

• Decomposition into biomes should be step 1 of generation, then you can use biome-info in further steps to provide large-scale variability
• Use Gradle task generateMap often
• Alter file Material2Hue.kt to add more colors to visualizer
• Alter the corresponding Main.kt to change resolution of render
• If running Minecraft, don’t forget to run deleteMap to regen map
• Stop server by typing stop

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Option 1 - Criteria

• Reasonable partition into biomes – 1pts
• Smooth transitions (in heightmap) between biomes – 1pts
• (self-created) Whittaker diagram used – 1pt

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Original Minecraft: Grassland, Jungle, Swamp, Badlands, Desert, Grassland biomes meeting

Acceptable solution:

A reasonable heightmap with transitions

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BIOMES:

Mountains (White)

Desert (Yellow)

Grassland (Green)

Sea (Blue)

Acceptable solution: Three biomes meeting (Sea, Grassland and Mountains)

Option 2 – Caves

• Use Perlin worms for Caves
• (apparently what Minecraft uses)
• Generates nice and long caves that are suitable for exploration

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• Optionally add deposits of Coal, Iron and Diamond underground

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Option 2 – Challenges

• Random walks:
• How to get all walks that intersect a given chunk (in infinite world)?
• Perlin worms:
• Thresholding a noise (e.g. to <-0.1,0.1>) in 3D creates “crumpled” planes. How to get worm-shaped structures?
• Ans: Use two Perlin worm (planes) and use their intersection

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Option 2 – Hints

• Start with generating just in 2D

Random walks:

• Use spherical coordinates

Perlin worms:

• Thresholding 3D noise results in a “cloth-like” shape (topologically deformed plane). How do you get the “worm-like” shape by using this method?
• Gradle task generateMapGrayscale may help visualize

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Option 2 - Criteria

• Methods that generate findable and explorable caves – 2pts
• Ores (Iron, Diamond, Coal) that spawn in different levels and in reasonable quantities – 1pt

Original Minecraft: X-ray view into Minecraft caves

Acceptable solutions using:

• Random walks
• 2D perlin worms
• 3D perlin worms

Try and guess which is which

Option 3 – Your Experiment!

• If there’s something cool you would like to try in Minecraft generation, come to discuss it and it may become your homework!

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• It should still be (at least in part) terrain generation

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• Examples:
• A different approach to biomes or caves
• Implementing Teardrop
• Some cool algorithm

Submission details

• Submit via this form
• Submit:
• one file of Kotlin or Java (human-readable, commented)
• If you want to use more classes, use internal ones
• describe all you have tried, what worked or didn’t, the problems you faced
• at least 3 screenshots (either rendered heightmaps or from Minecraft)
• how much time you spent with the project (will not be part of evaluation)

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• Deadline is 28.3.
• If you need more time, talk/write to me before the deadline

Questions / Problems

• Discord (private/public)!

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• One final recommendation:

Allocate more than one session to work on the project. If you get stuck on some issue, it’s good to clear your head for a bit and return to it later.