Unreal Engine Unreal Engine Performance Optimization & Profiling 1 — Questions and Answers
Question 1: Which Unreal Engine built-in tool provides a hierarchical CPU and GPU timing breakdown of a single frame to identify performance bottlenecks?
- Unreal Insights (Session Frontend) (Correct answer)
- Stat Unit
- RenderDoc integration
- GPU Visualizer
Correct answer: Unreal Insights (Session Frontend)
Unreal Insights captures detailed CPU/GPU timing traces with a hierarchical view for identifying per-system frame bottlenecks.
Question 2: What does the console command `stat fps` display in Unreal Engine?
- Current frames per second and frame time in milliseconds (Correct answer)
- GPU memory usage per render pass
- Number of draw calls per frame
- Active particle count in the scene
Correct answer: Current frames per second and frame time in milliseconds
`stat fps` overlays the current FPS and frame time (ms) directly on the viewport for quick real-time performance monitoring.
Question 3: What is the purpose of Level of Detail (LOD) meshes in Unreal Engine?
- Swap high-poly meshes for lower-poly versions as the camera distance increases (Correct answer)
- Generate collision shapes automatically from mesh geometry
- Reduce texture resolution on mobile platforms
- Merge multiple meshes into a single draw call
Correct answer: Swap high-poly meshes for lower-poly versions as the camera distance increases
LODs substitute progressively simpler mesh versions at greater camera distances to reduce GPU vertex processing cost.
Question 4: Which Unreal Engine feature automatically merges nearby static mesh draw calls into a single draw call to reduce CPU rendering overhead?
- Instanced Static Meshes (ISM / HISM) (Correct answer)
- Nanite virtualized geometry
- Distance Field Ambient Occlusion
- Mesh Draw Policy
Correct answer: Instanced Static Meshes (ISM / HISM)
Instanced Static Mesh and Hierarchical Instanced Static Mesh components batch identical meshes into a single draw call, dramatically reducing CPU overhead.
Question 5: What does the Unreal Engine console command `r.ScreenPercentage 50` do?
- Renders the scene at 50% of the screen resolution then upscales (Correct answer)
- Limits the frame rate to 50 FPS
- Reduces texture streaming pool to 50%
- Sets the LOD bias to reduce mesh detail by 50%
Correct answer: Renders the scene at 50% of the screen resolution then upscales
`r.ScreenPercentage` sets the internal render resolution as a percentage of the output resolution, with values below 100 reducing GPU cost via upscaling.
Question 6: In Unreal Engine, what is 'occlusion culling' and why is it used?
- Skipping rendering of objects hidden behind other geometry to save GPU cost (Correct answer)
- Removing objects outside the camera frustum
- Merging transparent objects into a single render pass
- Hiding actors beyond the far clip plane distance
Correct answer: Skipping rendering of objects hidden behind other geometry to save GPU cost
Occlusion culling tests whether objects are hidden behind opaque geometry and skips their draw calls entirely to save GPU processing.
Unreal Engine Unreal Engine Performance Optimization & Profiling 1
Which Unreal Engine built-in tool provides a hierarchical CPU and GPU timing breakdown of a single frame to identify performance bottlenecks?