HDRI Environment, Reflections and Tone Mapping

What this builds

A complete environment lighting and reflection pipeline for a Three.js scene: an HDRI equirectangular image loaded, converted to a prefiltered cubemap via PMREMGenerator, applied as both scene background and material environment map, with tone mapping and exposure tuned to produce physically plausible reflections on PBR materials.

• HDRI loaded via RGBELoader (.hdr) or EXRLoader (.exr) with proper linear-space handling
• PMREMGenerator produces the prefiltered mip chain needed for roughness-dependent reflections
• Scene background and material envMap configured independently (you can light with an HDRI without showing it)
• Tone mapping (ACES Filmic, AgX, Neutral, Reinhard, Linear) with exposure control
• MeshPhysicalMaterial exploiting envMap for clearcoat, transmission, iridescence, sheen
• Ground-projected environment for infinite-floor studio looks without geometry
• Reflection probes for localized reflections in multi-room scenes
• Proper disposal of HDRI textures and PMREMGenerator resources