What are LODs?

LOD (Level of Detail) is a technique found in all game engines that switches between different complexities of a 3D mesh over distance to reduce the amount of polygons that are needed to draw the scene.

These LODs, when setup correctly, will improve your games GPU performance!

Creating Levels of Detail

Firstly, to automatically generate different LODs for your skeletal mesh, open the mesh from the content browser.

Once the mesh is shown find the LOD Settings tab in the details section on the left.

Increase the “Number of LODs” slider to the amount that you want, then press the “Regenerate” button.

For this guide we chose four LODs. You can create and setup as many levels of detail you need for your specific mesh.

Setting up the Level of Detail

Firstly, inside the LOD drop down box, select the LOD level you wish to adjust.

Then, as LOD 0 is our full detail mesh, we want to change LOD 1 first.

Changing the LOD Distance

Inside the LOD Info drop down adjust the screen size value to the size we want for this LOD to be visible on the screen.

For this mesh we used these screen size values:

• LOD 0: 1.1
• LOD 1: 1.0
• LOD 2: 0.75
• LOD 3: 0.2

These values give the model a high quality look then quickly drops the mesh detail down over longer distances.

Reducing the Triangles

Inside the “LOD Info” drop down find the “Reduction Settings” section and adjust the “Percent of Triangles” value to what ever you require.

0.85 (15% reduction in triangles) works well for this skeletal mesh at LOD level 1.

For this guide we used these percent of triangle values:

• LOD 0: 1.0
• LOD 1: 0.85
• LOD 2: 0.45
• LOD 3: 0.1

Demonstration

Finally, with the settings used in this guide, the skeletal mesh will change between these LOD states based on the distance from the camera.

This reduced the complexity of the model, boosted your game’s performance whilst maintaining a high level of detail and quality at shorter distances.

Conclusion

Now your skeletal meshes are setup to dynamically change in quality over distance!

This simple setup drastically improves performance for lower end machines as is essential for an optimised game.

This technique is not a silver bullet for performance, but if implemented correctly, will increase the performance on many PCs when using high poly meshes.

This technique in conjunction with the static mesh level of detail setup will allow your game to contain more meshes and allow higher detail scenes without affecting performance heavily!

Click here to read the official documentation for the skeletal mesh reduction tool in Unreal Engine 4

Click here to setup automatically generating levels of detail for your static meshes in Unreal Engine 4

The post Easy LODs for Skeletal Meshes in Unreal Engine 4 appeared first on Couch Learn.

What are LODs?

LOD (Level of Detail) is a technique found in all game engines that switches between different complexities of a 3D mesh over distance to reduce the amount of polygons that are needed to draw the scene.

These LODs, when setup correctly, will improve your games GPU performance!

Creating Levels of Detail

Firstly, to automatically generate different LODs for your static mesh, open the mesh from the content browser.

Once the mesh is shown find the LOD Settings tab in the details section on the right.

In the LOD settings section, increase the “Number of LODs” section to the amount of different levels of detail you want Unreal Engine to automatically generate.

Before we start, untick the Auto Computer LOD Distance box.

For this guide we are using four levels of detail.

Once this is done, press the Apply Changes button.

Reducing the Triangles

Underneath the LOD Picker section of the detail menu, you will see the current selected LOD.

As the LOD is set to AUTO the current LOD visible is based on the distance to the camera in the editor’s viewport.

To change which LOD you are adjusting, press the LOD drop down and select which LOD distance you want to edit.

To change the reduction amount for the selected LOD, simply open the reduction settings tab.

To lower the quality of this LOD, change the “Percent Triangles” to a smaller percentage.

The best method is to lower the percentage slowly over the different LODs.

For this guide I have setup the Percent Triangles like so:
LOD 0: 100.0
LOD 1: 85.0
LOD 2: 65.0
LOD 3: 35.0

Setting the Distances

To switch between the different LODs, the engine uses the screen size setting. This determines how big the object is on the screen before it changes LOD state.

To change this value, select the LOD that you want to edit in the LOD Picker above and find the Screen Size box. Change this value to what you think is best for your meshes.

Its best to tweak these values and test until you find a sweet spot for the asset that you are configuring.

For this guide I have setup the distances like so:
LOD 0: 1.0
LOD 1: 0.55
LOD 2: 0.175
LOD 3: 0.035

Demonstration

Creating a blueprint that uses the newly adjusted mesh or just dragging in your new mesh into the level will automatically switch between the LODs.

As you can see in the video below the triangles used to render the object is heavily reduced.

Conclusion

Now your meshes fade between LOD states improving performance for your game!

This technique is essential for creating games that will perform well on many different power of PCs and other platforms.

To improve on this, enable LOD dithering to fade between LOD states smoothly. Click here for a link to our guide on using LOD Dithering in Unreal Engine 4!

For more information on LODs in Unreal Engine 4 click here for the official documentation: https://docs.unrealengine.com/en-US/Engine/Content/Types/StaticMeshes/HowTo/index.html

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