Setting Up LODs

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.

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, drag and drop the previously exported FBX file to the Asset Browser and perform the following to automatically create LODs based on the name postfixes:

1. Choose Combine By Postfixes in the Use LODs drop-down list.
2. Specify the maximum 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:

   

   Names of generated surfaces will be as follows: material_name + LOD_postfix.

4. Specify the minimum and maximum visibility distances for each LOD. Maximum visibility distance of each LOD should be equal to the minimum visibility distance of the next LOD. Maximum visibility distance of the last LOD should be equal to inf.

   

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

   

5. Specify the minimum and maximum fade distances for each LOD:

   

   • For _lod_0, leave the default Min distance and set the Max distance to 10 units. It will prolong the distance over which the LOD surfaces are still visible and provide smooth fading.
   • For _lod_1, set the Min distance to 10 units. After 5 up to 15 units, the second LOD surfaces will smoothly fade in. The Max distance set to 20 units. After 30 up to 50 units, the second LOD surfaces will smoothly fade out.
   • For _lod_2, set the Min distance to 20 units and leave the default Max distance. The third LOD surfaces will start to smoothly fade in from 30 to 50 units.

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:

• Configure the Min and Max Parent settings. In this tutorial, we use the default values of 1.

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

For each LOD surface, you should specify a visibility distance and a fade distance. The following image illustrates these distances and how they work.

For setting up the LOD surfaces, do the following:

1. Open the World Hierarchy window, and choose the added node.

2. In the Surfaces group of the Node tab (the Parameters window), choose the first LOD surface:

   

   • Set its Maximum Visibility distance to 5. It means that when the camera is 5 units away from mesh, the first LOD surfaces won't be visible.
   • Leave the Minimum Visibility distance at -inf. It means that no matter how close the camera comes to the mesh, the surfaces will still be visible.
   • Set the Maximum Fade distance to 10 units. It will extend the distance over which the LOD surfaces are still visible and provide smooth fading.

   

   Notice

   You can disable other LOD surfaces to see the result of the current LOD surface settings.

3. Choose the second LOD surfaces and:

   • Set the Minimum Visibility distance of the second LOD surfaces to start exactly where the Maximum Visible distance of the first LOD surfaces ends: at 5 units. It means that when the first LOD surfaces begin to fade out, the second LOD surfaces will be shown.
   • Set the Maximum Visibility distance at 30 units. After 30 units, the second LOD surfaces begin to fade out and the third LOD surfaces will be shown.
   • Set the Minimum Fade distance to 10 units. After 5 up to 15 units, the second LOD surfaces will smoothly fade in.
   • Set the Maximum Fade distance to 20 units. After 30 up to 50 units, the second LOD surfaces will smoothly fade out.

   

4. Choose the third LOD surfaces and:
   • Set the Minimum Visibility distance to 30 units. It means that when the second LOD surfaces begin to disappear, the third LOD surfaces will be shown.
   • Set the Maximum Visibility distance at 300 units. After 300 units the third LOD surfaces totally disappear.
   • Set the Minimum Fade distance to 20 units. The third LOD surfaces will start to smoothly fade in from 30 to 50 units.

   • Set the Maximum Fade distance to 50 units. After 300 units, the mesh will begin to smoothly fade out.

     Notice

     If you want to leave the last LOD surface always visible, set the Maximum Visibility distance to inf.

   

You should specify the same settings for each surface of the same LOD (if any). Different surfaces from one level of details should have the same settings to appear and disappear simultaneously.

Another important parameters of the LODs are Min Parent and Max Parent.

These parameters enable you to specify to which surface or node up in the hierarchy the minimum and maximum visibility distances will be measured. Use the default values of 1. In this case, all surfaces of the mesh will be switched simultaneously, because their distances will be measured not to surfaces themselves, but to the bounding box of the whole mesh.

Read here about these parameters.