Multithreaded Content Generation in “Simple Miner”

Timeline: June - July 2022

Description: Multi-threaded generation of endless voxel-based open worlds. Mine blocks and build structures.

Overview

The task was to explore procedural world generation for a Minecraft-like experience within a custom game engine. Development took place in three phases.

1. Create the infrastructure for voxel-based tiles. Add the ability to mine, collect, and place blocks.

2. Extend the engine to support a multithreaded job system.

3. Create specialized game-specific job types for world generation.

Gameplay

Blocks break progressively and display decals which convey their mining. After being broken, they drop physics entities that spin and float until the player collects them. It is from these pickups that the player can place blocks and build structures.

Multithreaded World Generation

Chunks are drawn closest to the player first and generated across a number of worker threads.

In order to preserve continuity across chunk boundaries for certain features like trees, Perlin Noise based generation was performed per chunk for a range greatly exceeding each chunk’s bounds. As a consequence, environment generation became too expensive to maintain a reasonable draw distance and hit frame rate. At this point, I implemented a basic job system, made environment generation thread safe, and set several job threads to focus only on chunk generation each frame.

Optimized Rendering

A view of the world from below the player showing the hidden surface removal.

To do some napkin math - my chunk’s dimensions were 16x16x128 blocks. If I drew each face of each block with 6 vertices each, 1.2 million vertices (24 bytes each) are sent to the GPU per chunk. In a world of a targeted 1,000 active chunks, certain mesh optimizations were required.

• Indexed Drawing

  • For each drawn face, 6-24 byte vertices can be represented by 4-24 byte vertices and 6 - 4 byte indices. By doing so, the volume of data sent to the GPU is reduced.

• Hidden Surface Removal

  • By building and drawing only the vertices which are possibly visible to the player, the total number of vertices drawn was observed to be 1/1000th of its previous total.

• Amortized Mesh Rebuilding

  • At a maximum, only a handful of chunk’s meshes were rebuilt each frame, and in priority order closest to the player. This strategy improves the player experience during heavy far away generation while maintaining responsiveness near the player.