Week 09: Optimization, HLOD's

Let’s see how we can get those sexy-looking frame rates. Don’t forget to have a look back at “EXTRA: Optimization” with the checklist. Link about UE5 Optimization:

https://dev.epicgames.com/community/learning/talks-and-demos/Vpv2/unreal-engine-optimizing-ue5-rethinking-performance-paradigms-for-high-quality-visuals-part-1-nanite-and-lumen-unreal-fest-2023⁠

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LOD - Level of Detail

This is pretty standard for every game, certainly for open world games.

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What is it?

With LOD’s you optimize the amount of triangles being rendered on the screen. The less percentage the object takes of the screen, the less triangles for that object. You can import and make your own LOD meshes if you want full control. This is not necessary for the exam, it is way more important that you know what LOD’s are and how they work. Around 8 LOD’s per object really is the max, because keep in mind, the engine needs to load these in at real-time.

Popping

When the correct LOD’s don’t get loaded in in time, ‘popping’ can appear. It means that another level of LOD all of a sudden gets loaded, and pops into the screen.

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Mipmapping

It works the same as LOD’s, but in this case for your textures.

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Overdraw

When you have translucent/masked materials (for ex. grass, leaves, etc..), the computer will need to look what is behind the translucent object and render that object as well. → This means that the computer will need to render out two objects. This can really weigh down on the performance. So whenever you can, use opaque materials. Don’t forget, we can do some shader tricks to fake translucency.

Nanite also works better with less overdraw.

Have a look here:

https://www.youtube.com/watch?v=m0AQBWAbjpo&ab_channel=HangryBunniesFromMars⁠

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Drawcalls

In short explained: A draw call is the CPU telling the GPU what to render. You can literally see it as the CPU calling to the GPU and saying “Hey, render me this object with this material.”

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Keep the amount of drawcalls reasonable. 1500 drawcalls is the max, 2000 is too much. The golden spot is around 1000. If you want to deep dive into rendering and drawcalls and etc..:

https://simonschreibt.de/gat/renderhell/⁠

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HLOD’s

To act the same as LOD’s, but you create clusters of meshes. This very handy for big environments, optimizing draw calls for ex.. With HLOD’s, you create one mesh with one material of the selected objects. Have a look here on how to create them:

https://docs.unrealengine.com/4.26/en-US/BuildingWorlds/HLOD/⁠