Participatory 3D modelling is like a 3D puzzle. It's a way for people to come together and build something imaginative and fun. Like a real-life Lego set, everyone puts together pieces (called "objects") to create a 3D object. They can also add details like trees, rocks, and other decorations to help make their 3D model look awesome. They can even add their own artwork to the 3D model to make it truly unique. When they're done, they can watch their 3D masterpiece come to life on the screen!