Setting Up Object LODs

• The Levels of Details section of the article on World Management.
• The Level of Details section of the article on Content Optimization.

As an example, we will use the tubes_constructor_chrome_1120.fbx model from the Oil Refinery demo (available in UNIGINE SDK Browser). This FBX consists of several meshes, each of which represents an element of the tubes constructor.

To create and set up LODs on importing the model into UNIGINE, first, you should perform the following in a 3D editor:

1. Create several meshes for different LODs of your model: a detailed mesh for the closest LOD and a number of less detailed meshes for farther LODs.
   Notice

   When naming the meshes, add a postfix to specify the LOD each mesh represents. For example: _lod_0 for the 1st LOD, _lod_1 for the 2nd LOD, etc.
   For example, for each mesh representing an element of the tubes constructor (10 meshes), there are 3 meshes representing LODs:

   

2. Export the meshes as an .fbx file.

To import the model into UNIGINE, click Import in the Asset Browser and choose the exported FBX file. In the Import FBX window, perform the following to automatically create LODs based on the name postfixes:

1. Enable the Combine By Postfixes option.
2. Specify the number of LODs stored in the FBX container (in our case, 3).
3. For each LOD define a postfix that will be used to group objects in an FBX file into a corresponding LOD.
   Notice

   The postfix must be the same as the one used when creating objects in a 3D editor.
   For the tubes constructor model, the following postfixes should be specified:

   

   The names of generated surfaces will be as follows: material_name + LOD_postfix.
4. Specify minimum visibility distance for each LOD. Maximum visibility distance of each LOD is equal to the minimum visibility distance of the next LOD. Maximum visibility distance of the last LOD is equal to inf.

   

   • For _lod_0, leave the -inf value. It means that no matter how close the camera comes to the mesh, the surfaces will still be visible.
   • For _lod_1, set the distance at 5 units. It means that when the camera is 5 units away from mesh, the first LOD surfaces won't be visible and the second LOD surfaces will be shown.
   • For _lod_2, set the distance at 30 units. After 30 units, the second LOD surfaces won't be visible and the third LOD surfaces will be shown.
   Notice

   The Minimum and Maximum Fade distances should be adjusted in the Node tab of the Parameters window when the model is added to the scene.

In the result, the FBX container with 10 meshes will be imported. Each mesh will have 3 surfaces representing LODs.

Add an exported model into the world as described here. All LODs will be already created and set up according to the specified import values:

If required, adjust the LODs surfaces in the Node tab of the Parameters window:

1. Set the Minimum and Maximum Fade distances for each LOD:
   • For the first LOD surfaces, leave the Minimum Fade distance 0 and set the Maximum Fade distance to 10 units. t will prolong the distance over which the LOD surfaces are still visible and provide smooth fading.
   • For the second LOD surfaces, set the Minimum Fade distance to 10 units. After 5 up to 15 units, the second LOD surfaces will smoothly fade in. The Maximum Fade distance set to 20 units. After 30 up to 50 units, the second LOD surfaces will smoothly fade out.
   • For the third LOD surfaces, set he Minimum Fade distance to 20 units. The third LOD surfaces will start to smoothly fade in from 30 to 50 units.
2. Set the Min and Max Parents. Within this tutorial, we use the default values of 1.

Try to move the camera forward/backward to check how LODs are switched.

To export the mesh with LODs, do the following:

1. In a 3D editor, create a detailed model and a number of models with a low number of polygons. For example, you can just copy the existing detailed model and reduce the number of polygons.
   Notice

   You should create a separate LOD for each part of the model to which a unique material is assigned.

   As an example, we will use the model of an oscilloscope from Superposition benchmark (available via UNIGINE SDK Browser). This model already contains 3 LODs.

   

   10109 polygons	5004 polygons	2583 polygons
   LOD 0	LOD 1	LOD 2

2. Generate LODs according to a pipeline used by your 3D editor. For example, in 3ds Max, you should group meshes representing LODs and then create LODs via the Level of Detail utility.
3. Export the model with LODs as an *.fbx file.

To import the model into UNIGINE:

1. Click Import in the Asset Browser and choose the exported FBX file.
2. In the Import FBX window, enable the Merge Static Meshes option. Otherwise, LODs will be imported as separate meshes, not surfaces.
3. Import the model.

Add an exported model into the world as described here. By default, all surfaces (LODs) are visible at the same time:

The surfaces of the exported model that represent LODs can be found in the Node tab of the Parameters window:

This section explains how to set up LODs of the mesh to smoothly switch a high detailed LOD to a low detailed when the camera begins to move away from the mesh. LOD surfaces have 3 parameters:

• Parents
• Visibility distances
• Fade distance

Visibility and Fade Distances

Minimum and Maximum Parents