# LOD Generator This guide explains how to use the **VR LOD Generator** in SimLab Composer to optimize large scenes for a smooth, high-performance VR experience. --- ### What is LOD (Level of Detail)? **LOD** is a system that swaps a 3D model with lower-polygon versions in real-time to save processing power. The switch between levels is determined by two main criteria: - **Distance:** How far the user is from the object. - **Screen Coverage:** How much space the object takes up in the user's field of view. --- ### 1. Pre-LOD Optimization Before generating LODs, you must reduce "draw calls" (the number of separate objects) and clean up materials. - **Selection Rule:** Expand groups and **select individual assemblies** (e.g., all separate chairs) rather than just the single top-level parent assembly. - **Step 1 (Materials):** Merges identical materials and optimizes texture sizes/compression. - **Step 2 (Merge Objects):** Combines parts within each assembly to reduce complexity while keeping objects distinct from one another. --- ### 2. Identifying "Heavy" Objects The plugin provides a surgical way to find which objects are taxing performance: - **Filter:** Set a **Minimum Polygon** count to populate the plugin table with complex objects. - **Analyze & Zoom:** View exact polygon counts in the table. **Clicking any item in the table** will automatically zoom the camera to that object in the scene for inspection. --- ### 3. Creating & Managing LODs Define your decimation percentages for each level. Note that **LOD 0** represents the model when the user is closest to it; decimating this level reduces the polygon count of the "original" model itself. - **LOD 0:** Initial decimation to optimize the model at its closest distance. - **LOD 1 & 2:** Increasing levels of reduction for mid-to-far distances. - **LOD 3:** Enable the **Hide** option to completely remove distant objects from the render. - **Global Settings:** Use this to determine if the system swaps levels based on **Distance** or **Screen Coverage**. Watch This Tutorial to Learn more