Instancing

Instancing is a technique where an object’s geometry is stored in memory only once, and every copy in the scene is described just by its own position, rotation and scale. A thousand identical chairs are kept not as a thousand objects but as one chair plus a thousand placements. That is what lets enormous scenes render on machines that would otherwise run out of memory.

Where instancing helps

Architectural scenes are full of repetition: facade panels, window frames, chairs, light fittings, trees and blades of grass. A forest, a stadium stand or a large housing development would fill the memory of most computers without instancing. Scatter tools rely on it behind the scenes when they spread thousands of plants across a terrain. In real-time engines, copies of the same object are sent to the graphics card in one batch, which keeps playback smooth.

Its link to modeling software

Components in SketchUp and blocks or referenced copies in other programs follow the same idea: the definition is made once and the copies point to it. Edit one and they all update, which saves time and keeps the file small. Most render engines recognize this structure and turn it into instances. Copying a repeated object as separate groups instead of components throws that advantage away. For hardware advice on heavy scenes, read about the best laptop for architectural rendering.