Object Instancing

Jiayi Sun

Updated Files

• include/nori/instance.h
• include/nori/reference.h
• src/instance.cpp
• src/reference.cpp
• src/scene.cpp

Implementation

For object instancing, I implement it that supports single-object instancing based on a reference shape. The Instance class uses a Reference object as the base geometry, applying transformations only at the instance level. Geometry operations like intersection tests and surface sampling are handled by the reference object, with rays and points transformed to the instance's local frame for calculations and then back to world space. Each instance shares the same reference geometry but can have independent transformations

Validation

For validation, I compare the results of object instancing with three separately defined spheres, ensuring that both cases produce identical output images. To further verify the correctness of transformations, I apply textures to the spheres and confirmed that the rotation and alignment were accurate, as the textures appear correctly oriented on the instanced spheres.

I also test with 20 spheres and observed minimal differences in speed (from 6.8m to 6.6m) and memory usage of the whole Nori process (both are 2.8 GB). This suggests that the performance benefits of instancing may become more noticeable in more complex scenes.