Nori 作业

Nori is a minimalistic ray tracer written in C++. It runs on Windows,
Linux, and Mac OS and provides a foundation for homework assignments
in the course Advanced Computer Graphics taught at EPFL.

Nori是用于在教学上的光线追踪渲染器，里面有5个编程作业。

开发环境

• MacBook Pro (13-inch, 2017, Four Thunderbolt 3 Ports)
• Processor 3.1GHz Dual-Core Intel Core i5
• Memory 16GB
• Graphics 1536MB
• Softwares
  • Visual Studio Code
  • CMake
  • git
  • Fork - a fast and friendly git client for Mac and Windows
  • GitHub - Tom94/tev: High dynamic range (HDR) image viewer and comparison tool

Assignment 1 : Downloading and Compiling Nori

• 实现NormalIntegrator
  

支持多个网格体

代码目前支持单一个mesh的场景，作业4开始需要支持多个mesh的场景，因此可以在作业一后优先支持多个mesh的扩展。支持多个mesh的场景的扩展代码，仔细阅读Accel后是一个比较简单的任务。

• 扩展accel.h/accel.cpp
• 实现空的area.cpp
• 修改scene_pa4_cbox/cbox-whitted.xml的integrator的名字为normals
• ./nori box-whetted.xml
  

Assignment 2 : Ray Tracing Acceleration Data Structures

performance comparison

• width x height: 68x68 with 2 sample per pixel(spp)
• brute force method took 1.8m to render the scene.
• ochre method
  • took 378.ms and 8.9MB to build octree with 7408 nodes and 27248 leafs given depth <= 6 and triangles <= 10
  • took 28.ms to render the scene

Results

scenes/pa2/ajax-normals.xml

• 768 x 768 with 32 spp
• took 376ms and 8.0MB to build octree
• took 29.8s to render the scene

•  27 triangles per node(including leafs)
  

scenes/pa4/cbox/cbox-whitted.xml

• change integrator from whitted to normals
• 800 x 600 with 512 spp
• took 10ms and 466KB to build octree with 1233 nodes and 6051 leafs
• took 1.7m to render the scene
• 5 triangles per node
  

Notes

• the intersection of bounding box and triangles
  • the vertices of triangles may be not in bounding box

Assignment 3 : Monte Carlo Sampling and Ambient Occlusion

Monte Carlo Sampling

Square

Tent

Disk

Sphere

HemiSphere

CosineHemiSphere

Beckmann

Two simple rendering algorithms

Point lights

• rendering with position : -20 30 -20, energy : 3.76e3 3.76e3 3.76e3

Ambient occlusion

• scenes_pa4_cbox/cbox-whitted.xml
• integrator = ao
  

Notes

• Importance Sampling - PataBlog

Assignment 4 : Distribution and Whitted-style Ray Tracing

Area lights

Pass

Distribution Ray Tracing

• scenes_pa4_motto/motto-diffuse.xml
  
• scenes_pa4_cbox/cbox-distributed.xml
  
• scenes_pa4_tests/test-mesh.xml
  
• scenes_pa4_tests/test-mesh-furnace.xml
  
• notes
  • sample a barycentric coordinates by Barycentric Coordinate for Surface Sampling
  • the three vertices of triangle may not be passed in the intersection.

Dielectrics

Pass.

Whitted-style ray tracing

• scenes_pa4_cbox/cbox-whitted.xml
  
• change the bsdf of two spheres
  
• scenes_pa4_motto/motto-dielectric.xml
  
• notes
  • stuck very long in the return value of the sample function in dielectric
  • https://graphics.stanford.edu/courses/cs148-10-summer/docs/2006--degreve--reflection_refraction.pdf
  • https://www.scratchapixel.com/lessons/3d-basic-rendering/introduction-to-shading/reflection-refraction-fresnel
  • https://blog.demofox.org/2020/06/14/casual-shadertoy-path-tracing-3-fresnel-rough-refraction-absorption-orbit-camera/

Assignment 5 : Path Tracing, Microfacet Models, and Multiple Importance Sampling

Microfacet BRDF

• Ajax-smooth.xml
  
• Ajax-rough.xml
  

Path_mats Brute force path tracer

• cbox_mats.xml
  
  
• veach_mats.xml
  
  
• table_mats.xml
  
  

path_ems Path tracer with next event estimation

• cbox_ems.xml
  
• veach_ems.xml
  
• table_ems.xml
  

References

• Importance Sampling - PataBlog
• Barycentric Coordinate for Surface Sampling
• smallpt: Global Illumination in 99 lines of C++