Creating LODs

task summary...

Levels of Detail

You can specify varying levels of detail for an object depending on the viewing distance; this increases performance by allowing fewer polygons to be drawn for an object that is far away. The Level of Detail Editor provides an interactive means for creating varying levels of detail and viewing the transitions in realtime. For more information, click the following topics: Level of Detail Editor or Polygon Reduction Editor.

Level Of Detail Editor

The Level of Detail (LOD) Editor is a tool that allows you to

The mental model of the LOD Editor is similar to an animation flipbook. LOD's are pages (levels) ordered from closest (highest detail) to farthest (lowest detail). When you move away from the object, you flip through the levels as your distance increases. You can add and remove pages, or edit objects on a page. You cannot, however, add objects to an existing page.

Activate the LOD Editor by clicking on the LOD button on the menu bar, or by choosing "Level Of Detail Editor" from the Appearance menu. When you move the cursor over the LOD button the following message is displayed: Invoke Level Of Detail Editor

Note: The triangle count for the currently displayed object appears directly above the preview area in the LOD Editor.

For information on how to use the Level of Detail Editor, click a topic:

Import a File as a New Level

To import a file as a new level into the Level Of Detail Editor, follow these steps:

  1. Activate the LOD Editor.
  2. Choose "Import New" from the Level menu.
  3. Type the pathname for the object file in the Selection field, or browse through the directory structure until you find the name of the file you want. The selected file is highlighted in black.
  4. Click the OK button. The file appears in the LOD Editor window as a new level. The initial distance at which this new level becomes active is automatically calculated and appears on the transition slider at the bottom of the window.

Paste a New Level

To paste the contents of the clipboard as a new level into the Level Of Detail Editor, follow these steps:

  1. Select a displayed object in the WebSpace Author window, or from the Text modeler or Shape modeler applications.
  2. Choose "Copy" from the (appropriate) Edit menu.
  3. Activate the LOD Editor.
  4. Choose "Paste New" from the LOD Editor Edit menu.

Duplicate a Level

To duplicate a level of complexity of an object using the LOD Editor, follow these steps:

  1. Activate the LOD Editor.
  2. Display the object in the LOD Editor by importing a file or pasting an object into the window.
  3. Choose "Duplicate Level" from the Level menu. An exact copy of the object is used to create another level. The transition slider at the bottom of the window shows the distance in meters (from the camera) that this level replaces the original object for viewing.
  4. Select portions of the object and alter them so that they create a simpler version of the original object.

    Some notes:

The following examples show the three levels of an object. Notice the difference in the triangle count between the first and third levels. The original triangle count is 1032; the third level triangle count is only 88.

Interactively Set Viewing Distance

To interactively set the transition distance of a level of an object, follow these steps:

  1. Activate the LOD Editor.
  2. Create a level for the object by importing a new version, pasting a new version, or duplicating a previous level and editing it to simplify.
  3. Move the cursor over the distance marker on the bar graph at the bottom of the screen. It turns red.
  4. Hold down the left mouse button and drag the marker to the desired distance. You can see the marker distance change as you move the marker. The transition distance change takes effect immediately. You may see the main view redraw if your changes affect the main view due to its camera distance.
  5. Adjust the rest of the levels accordingly.
  6. To view the settings, choose "View LOD Transitions" from the Edit menu. A viewing slider appears on the version distance transition slider.
  7. Move the cursor over the viewing slider, and drag the slider along the graph. The version levels swap out at the distances marked on the slider, and the transitions are shown in the window as they swap.

Previewing Levels

Once you have created several levels and set the viewing distance of each level, you can flip through the levels and preview how the transitions will appear as someone moves through the scene. There are several key points to understand about the transition preview tool:

To automatically flip through the established level of a model to preview their transitions, follow these steps:

  1. Click the eye icon in the LOD Editor.
  2. Click and drag the transition slider at the bottom of the window. You can also use the dolly thumbwheel to transition through the levels.
  3. Watch in the preview area of the window as the models transition at their set distances.

The portion of the window with the transition slider is shown in the illustration below.

The following examples show the previews of three levels of detail for an object.

Showing All LOD Objects

Once you have created levels of detail for several objects within a scene, you may want to take an inventory of them before continuing with the scene construction. You can do this easily by choosing "Show LOD" from the View menu.

Note: This is an important tool for verifying that your transitions are taking place at reasonable distances. Using Show LOD helps you quickly identify objects which LOD transitions do not happen at appropriate distances. You may also find that objects close to each other are transitioning between levels at very different distances. You may wish to make those transitions more equal.

The level of the LOD for each object is displayed according to the viewing distance from the camera. Objects that have LODs are rendered in a color depending on the level, or distance at which they are displayed. The color coding for levels is as follows:

Red: first level; closest to the camera

Gold: second level

Yellow: third level

Green: fourth level

Light Blue: fifth level

Dark Blue: sixth level

Purple: seventh level; furthest away from the camera

Eighth level: color cycle repeats

The colors cycle back to red after purple. This means that an object that is very, very far away could be red, as well as an object that is up close. There would have to be eight levels to the object for this to happen, however.

The following illustration shows a scene with chess pieces having different LODs. The closest chess piece appears red, the gold piece is next closest, and the yellow pieces are furthest away.