Fully procedural Scottish Highland steam train scene crossing a stone viaduct

[Note: the creator shared a partial prompt. Wording below is theirs.] GOAL: PROJECT: HIGHLAND EXPRESS Fully Procedural 3D Steam Railway Experience You are a senior Three.js developer, procedural 3D artist, animation engineer, and technical artist. MOTION: Build a visually stunning, fully procedural 3D railway scene featuring a detailed Victorian steam locomotive crossing a massive stone viaduct in the Scottish Highlands. The result should resemble a beautifully crafted miniature railway diorama brought to life, with cinematic lighting, rich environmental details, realistic mechanical animation, and atmospheric depth. TECHNOLOGY: Three.js TypeScript Vite Custom BufferGeometry Procedural shaders and materials Instanced meshes for environmental details CRITICAL REQUIREMENT: Everything must be generated procedurally using code. Do not use premade 3D models, downloaded assets, external image textures, or model files. Generate geometry, materials, terrain, vegetation, architectural structures, and animations programmatically. 1. STEAM LOCOMOTIVE Create a highly detailed Victorian steam locomotive with convincing proportions and intricate mechanical components. Include: Cylindrical boiler with detailed metal bands and seams. Large smokebox and front door with bolts and hinges. Tall chimney with a detailed rim. Steam dome and safety valves. Headlamp with a warm glow. Detailed cowcatcher and front buffers. Multiple large driving wheels with spokes. Smaller leading and trailing wheels. Connecting rods and coupling rods. Pistons and crank mechanisms. Cab with windows, controls, and interior details. Handrails, pipes, rivets, vents, and metal fittings. Procedurally generated paintwork and weathering. Use custom geometry and carefully modeled details rather than simple primitives as finished components. The locomotive must have a recognizable silhouette and convincing industrial construction. 2. MECHANICAL ANIMATION The locomotive must move continuously along the railway track. Implement: Rotating driving wheels. Connecting rods synchronized with wheel rotation. Correctly coordinated crank movement. Animated pistons where visible. Subtle locomotive suspension movement. Smoke emitted from the chimney. Steam escaping from valves and pipes. Headlamp illumination. Wheel rotation and connecting-rod movement must remain mechanically synchronized with the train's speed. 3. PASSENGER CARRIAGES Create several classic Victorian passenger carriages behind the locomotive. Each carriage should feature: Detailed body panels. Wooden or painted metal construction. Repeated windows. Roof curvature and roof seams. Doors, steps, buffers, and couplings. Underframe details and wheel assemblies. Warm interior lighting. Arrange the carriages along the railway track and make them follow the locomotive smoothly. All carriages must maintain consistent spacing and alignment when traversing curved tracks. 4. MASSIVE STONE VIADUCT Build a spectacular railway viaduct crossing a deep Highland valley. Include: Multiple massive stone arches. T