Procedural Terrain Generation in Unity: An Introduction

Creating stunning terrains for your game can be challenging, especially when you want to strike the perfect balance between handcrafted precision and procedural generation. This article introduces an approach to procedural terrain generation in Unity while keeping it simple and efficient, leveraging the power of shaders and coroutines.

Why Shaders for Procedural Generation?

Implementing procedural terrain generation often requires generating complex noise like Voronoi, Perlin, or fractal noise. Unity's C# doesn't natively support these noises, and creating them from scratch can be computationally expensive. However, Unity's Shader Graph or custom shaders provide built-in support for such noises, making them an excellent choice for generating heightmaps.

Using Shaders for Performance

Shaders are highly optimized for parallel computation on the GPU, enabling them to process complex mathematical operations efficiently. By rendering noise to a Render Texture using a shader, we can offload the generation process to the GPU, significantly improving performance. Once the texture is generated, it can be sampled and used in terrain manipulation.

Key Points:

• Noise generation happens in the shader and is rendered into a Render Texture.
• The texture is sampled once at the start to avoid runtime performance overhead.
• Since reading texture pixels can be computationally expensive, coroutines are used to process the heightmap progressively without blocking the main thread.

Combining Procedural and Handcrafted Terrains

One of the most powerful aspects of this system is its flexibility to blend procedural generation with handcrafted elements. By defining two ranges on the terrain, you can set a range where procedural terrain applies and the set middle of that range as fully procedural. Both range ends mark the end of procedural blending. Heights of the base terrain below or above those heights are fully handcrafted.

Blending Handcrafted and Procedural Heights

The system uses a blending function that:

1. Samples the handcrafted heights as a base.
2. Blends procedural noise based on a fall-off mask and custom logic.
3. Allows the artist to control how much influence the handcrafted elements retain versus the procedural components.

A Modular Approach to Terrain Tools

The script in this system also integrates with external procedural tools that complement the terrain generation system, enhancing the final output. Examples include terrain painting tools or vegetation spawners that add further customization and polish to your terrains.

Coroutine-Based Processing

While Shader Graph efficiently generates the noise, Unity's Texture2D.GetPixel() can be expensive when sampling pixels from the rendered texture. To mitigate this, the script processes terrain heightmaps incrementally over multiple frames using coroutines. This ensures that the main thread remains responsive, even for high-resolution terrains.

Advantages of Using Coroutines:

• Avoids blocking the main thread during terrain generation.
• Allows terrain updates to happen smoothly over multiple frames.
• Scales well with larger terrains or higher resolutions.

Key Takeaways for Optimizing Procedural Terrain

1. Use Shaders for Noise: Leverage Unity’s Shader Graph to generate and render noise to a texture for better performance.
2. Blend Handcrafted and Procedural: Incorporate ranges where the terrain transitions between handcrafted features and procedural elements to maintain control over important terrain features.
3. Process Incrementally:Use coroutines to process terrain data without affecting the game’s runtime performance
4. External Tools:Combine this system with procedural tools to add further customization and polish to your terrains.