In this lesson, you will learn how to fine-tune NavMesh generation parameters to strike the perfect balance between high-fidelity navigation and optimal runtime performance.
When you drop a NavMeshBoundsVolume into your level, Unreal Engine performs a complex voxelization process to calculate where your AI can walk. If your environment is massive or highly detailed, the default settings might be too expensive to calculate or too "loose" to be accurate. We control this via the Project Settings > Navigation Mesh tab.
Balancing Accuracy vs. Performance
The two most critical parameters for this trade-off are Cell Size and Cell Height:
- Cell Size: This represents the horizontal resolution of the voxel grid used to generate the mesh. A lower value makes the navigation mesh wrap more tightly around geometry (like thin stairs or narrow alleyways), but drastically increases memory usage and build time.
- Cell Height: This defines the vertical resolution. Reducing this allows your AI to navigate under low-hanging obstacles or over small ledges, but at the cost of higher CPU overhead during navigation rebuilds.
Agent-Specific Tuning
Beyond global project settings, you should configure your NavMesh Recast settings to accommodate specific character archetypes. For example, if you have a giant boss enemy, you can define a NavAgentProperties profile that sets a higher AgentRadius and AgentStepHeight.
// Example of checking navigation properties in your AI Controller
if (GetPathFollowingComponent())
{
float Radius = GetPathFollowingComponent()->GetMoveAgentProperties().AgentRadius;
UE_LOG(LogTemp, Log, TEXT("Current AI Nav Radius: %f"), Radius);
}
By adjusting these values, you avoid the "navigation sprawl" where the NavMesh generates over areas where the AI is physically too wide to pass, or fails to generate in critical transition zones. If your NavMesh build is taking too long during development, prioritize increasing your Cell Size until you reach the threshold where the AI stops clipping through walls, then stop there. Remember: navigation is a simulation, not a pixel-perfect representation of your geometry.
Key Takeaway: NavMesh generation is a resource-intensive voxelization process; always tune your Cell Size and Agent Radius to match the physical footprint of your AI rather than the visual mesh of your environment.