What problem does it solve? Setting up realistic lighting in Three.js requires choosing the right light types, tuning shadow cameras, and configuring environment maps, which involves many error-prone parameters and common pitfalls like shadow acne. ## Core Features & Use Cases - Light Type Reference: Covers AmbientLight, HemisphereLight, DirectionalLight, PointLight, SpotLight, and RectAreaLight with constructor parameters and runtime properties. - Shadow Configuration: Explains enabling shadow maps, sizing shadow cameras, fixing shadow acne with bias settings, and optimizing shadow performance. - Environment Lighting (IBL): Shows HDR loading with RGBELoader, PMREM generation, cube textures, and light probes for realistic PBR lighting. - Use Case: When building an outdoor 3D product viewer, use this Skill to set up a directional sun light with tuned shadows, hemisphere sky lighting, and an HDR environment map. ## Quick Start Ask the AI to add a directional light with soft shadows and an HDR environment map to your Three.js scene.