Optimizing Performance with a Custom Vegetation System for Thrive: Heavy Lies the Crown

In large-scale strategy games like Thrive: Heavy Lies the Crown, vegetation systems play a critical role in bringing the world to life. From dense forests to sprawling grasslands, these systems create the illusion of a living, breathing ecosystem. However, rendering thousands of trees, shrubs, and grass blades can quickly become a performance bottleneck, especially on lower-end hardware.To tackle this challenge, the Thrive development team engineered a custom vegetation system optimized for both visual fidelity and performance. Here’s how they did it, with key techniques and examples.

🌿 Why a Custom Vegetation System?

Most engines provide built-in vegetation tools, but they often lack the flexibility required for massive strategy game maps. In Thrive, the game world supports:

• Dynamic seasons (spring bloom, autumn leaves falling)
• Terraforming by players (clearing forests, planting crops)
• Large view distances where players can zoom in on individual trees or out to see entire kingdoms

These demands pushed default solutions (like Unity’s Terrain Trees or Unreal’s Foliage Tool) to their limits. The custom system needed to balance density and performance without sacrificing immersion.

🏞️ Key Features of the Custom Vegetation System

1. Level of Detail (LOD) and Imposters

To keep frame rates high, Thrive uses aggressive LOD switching:

• High-poly models are used only when the camera is close.
• At medium distances, simplified meshes with baked normal maps take over.
• At extreme distances, entire forests are replaced by 2D billboard imposters with subtle animations to simulate wind movement.

This technique reduced draw calls by over 60% during benchmark tests.Example: When viewing a dense forest from afar, the system renders only flat textures with fake shadows instead of thousands of 3D trees.

2. Dynamic Vegetation Streaming

Instead of loading all vegetation at once, Thrive streams in vegetation only within a defined radius around the camera. 

This system:

✅ Prevents GPU overload on vast maps

✅ Allows seamless exploration without noticeable pop-ins The streaming is powered by a quadtree partitioning system, ensuring efficient memory usage even with maps over 100km².

3. Procedural Generation with Handcrafted Control

While procedural tools generate forests and fields, designers still need manual control for story-driven zones:

• Forests are procedurally seeded using noise functions (Perlin, Voronoi)
• Specific regions (like royal gardens or cursed swamps) use hand-placed assets
• Player actions (deforestation, farming) dynamically update vegetation in real time

This hybrid approach provides realism without losing design precision.

4. GPU Instancing & Culling Techniques

Thrive leverages GPU instancing to render thousands of identical vegetation objects with a single draw call. Combined with:

• Frustum culling (hides objects outside the camera view)
• Occlusion culling (hides objects blocked by other objects)

…these optimizations dramatically improved frame rates, especially during late-game when kingdoms expand across the map.

📊 Performance Gains: Before vs. After

🎮 The Player’s Perspective: Seamless Immersion

Thanks to these optimizations, players in Thrive: Heavy Lies the Crown can enjoy:🌲 Dense forests that feel alive

🌾 Fields swaying with dynamic wind effects

🍂 Seasonal changes without performance drops

🚜 Real-time vegetation updates as players clear land or grow crops All while maintaining smooth gameplay even on mid-tier PCs.

💡 Lessons for Other Game Developers

Thrive’s approach isn’t unique to its genre—it’s a blueprint for any game with:

• Open worlds
• Dynamic ecosystems
• Player-modifiable terrain

Key takeaway: Invest in a custom system early if vegetation is central to your visual storytelling.

🔥 Final Thoughts

The custom vegetation system in Thrive: Heavy Lies the Crown is a testament to smart design and technical ingenuity. It delivers stunning visuals while keeping performance in check, proving that beauty and efficiency can coexist. As open worlds grow bigger and players demand richer detail, such systems will become essential for future strategy and simulation titles.