Creating a LOD
Once your project has loaded, navigate to the Meshes folder inside the Content Browser and find the asset named FirstPersonCube_Rounded.
Once you have found that asset, open it inside the Static Mesh Editor by either double-clicking or by right-clicking and selecting Edit from the context menu that appears. Now you should have something that looks similar to what is shown below.
Once you have the asset open in the Static Mesh Editor, locate the Details panel. It is in the upper right corner by default. Once you find it, it should look like what is shown below:
The top section is labeled LOD0. LOD is a zero-based system, so LOD0 will be the first entry, LOD1 would be the second, and so on. LOD0 is the base LOD of the mesh and will be the only one that is used if the mesh only has 1 LOD, which this mesh does right now. Next, we are going to change that.
The section directly under that one is named LOD Settings. In this section, there are a few options we are going to go over. The first one is Number of LODs. It is at 1 by default and will increase as you import LODs. This value also can be editable if auto mesh reduction is available. However, in order to use this feature you must first obtain a license from Simplygon.
The next option we will go over is LOD Import. This option will give you a drop down menu similar to this: Select Import LOD Level 1. This should open up a window that allows you to browse to the .FBX file mentioned earlier in this How-to. Browsing to and selecting the .FBX file will import that mesh LOD1, or the second LOD. Once you have done this, you will see a pop-up notification at the bottom right of your screen that should look similar to this:
In this example we are only importing 1 LOD which will give us a total of 2, but you can import more if you wish. To do so, simply click on the drop down menu for LOD Import and select Import LOD Level X where X equals whichever LOD was the next one that you wanted to import. You could also reimport any LOD you had already imported. If you wanted to import another mesh for LOD1 instead of the one you already had imported, just click on the drop down menu for LOD Import and select Reimport LOD Level 1. If you clicked on the drop down menu now, your options would look like this:
Now that the mesh for LOD1 has been imported, we are going adjust a few of the values to demonstrate the power of LODs. The first option inside the LOD Settings section of the Details panel we are going to look at is Auto Compute LOD Distances. What this does is tell when to switch from one LOD to another by equally dividing the percent of screen size by the amount of LODs. For example, in this case, we have two LODs, so when the mesh takes up 50 percent or more of the screen, LOD0 will appear. When the mesh takes up less than 50 percent of the screen, LOD1 will appear. If there are three LODs, than LOD0 will appear when the mesh takes up 66.7 percent of the screen or more, LOD1 will appear between that value and 33.3 percent, and LOD2 will appear if the mesh takes up less than 33.3 percent of the screen. This may not be very helpful in this case however as the mesh we are using will more often than not take up less than 50 percent of the screen. We can manually change these values, however, by unchecking Auto Compute LOD Distances and manually adjust the Screen Size value for the individual LODs
For the purposes of this demonstration, we are going to uncheck Auto Compute LOD Distances. Once you have done that, find the Screen Size value under LOD1 and change it to 0.01. This means that when the cube mesh that we have in our level takes up less than 1 percent of the screen size, our cube will switch to the mesh you imported as LOD1 (In this example, a sphere.) We can also change the material for each LOD, as well. Just to further demonstrate the power and usefulness of LODs, we will change the material of LOD1 to M_Metal_Gold.