BiteSizedChunks.comLearn one small thing at a time.
Course contentsShow
← Unreal Engine Game Development
Lesson 789 of 88011. Performance Profiling and OptimizationFree lesson

Reducing Draw Calls with Mesh Batching

Combine individual static meshes into single draw calls using Actor Merging to significantly lower the overhead on the graphics API.

In this lesson, you will learn how to drastically reduce the rendering overhead of complex environments by using Actor Merging to consolidate individual static meshes into single, performance-optimized draw calls.

The Problem: Draw Call Bottlenecks

Every time the engine sends an instruction to the GPU to draw a unique mesh, it incurs a "Draw Call"—a command that consumes CPU time. If your scene is populated with thousands of individual actors (like modular building walls, debris, or scattered props), the CPU spends more time talking to the graphics API than the GPU spends rendering pixels. This is a classic CPU-bound bottleneck.

The Solution: Actor Merging

Unreal Engine provides an Actor Merging tool that allows you to bake multiple disparate static meshes into a single new StaticMesh asset. By combining these, you essentially tell the engine: "Instead of rendering 50 separate objects, render this one combined mesh."

To perform this in the editor:

  1. Select all the static mesh actors you want to combine in the Level Viewport.
  2. Navigate to Window > Developer Tools > Merge Actors.
  3. In the Merge Actors panel, choose your settings:
    • Batch Type: Select "Merge Actors" to combine them into a single asset.
    • LOD Selection: Choose the highest quality LOD.
    • Pivot Point: Choose "Center" or "First Actor" to ensure proper placement.
  4. Click Merge Actors and save the new asset.

Practical Impact

When you replace 50 distinct actors with one merged mesh, your rhi.DrawCalls count in your stat rhi readout will drop from 50 to 1. This significantly lowers the driver overhead.

Note: Be careful with this technique—merging actors removes their individual Cull Distance settings and can break Nanite or lightmap optimizations if not handled correctly. Only merge objects that share the same material or are intended to always be visible at the same time. If they have different materials, use the Merge Materials setting during the process to generate a texture atlas, ensuring the resulting mesh still renders in one draw call.

Key Takeaway: By consolidating static geometry into a single mesh asset via the Merge Actors tool, you reduce the CPU-side overhead of individual draw calls, allowing your game to maintain a higher frame rate in complex environments.