Opacity in 3D models is less common because rendering transparent or semi-transparent materials requires extra computational power and complex shading, which hurts performance.
Real-time apps like games or AR/VR prioritize speed, so they limit opacity to avoid slowdowns from tasks like alpha blending or light interaction—offline rendering (e.g., movies, static visuals) uses more opacity since performance isn’t urgent.
If you need opacity, start with simple elements (e.g., thin glass) and use optimizations like alpha clipping for sharp edges to balance quality and speed in real-time scenarios.