CSCI780 Advanced Topics: Computer Graphics

Homework 2

Name: Yongsen Ma, Email: yma@cs.wm.edu

References

This homework implements the Smooth Surface and Microfacet BRDF models in the paper by [Löw et al] using the mitsuba render system.

1. Mitsuba. Physically Based Renderer. mitsuba-renderer.org
2. Joakim Löw, Joel Kronander, Anders Ynnerman, and Jonas Unger. 2012. BRDF models for accurate and efficient rendering of glossy surfaces. ACM Trans. Graph. 31, 1, Article 9 (February 2012), 14 pages. DOI=http://dx.doi.org/10.1145/2077341.2077350

Folder Structure Summary

Some folders and files are not listed.

mitsuba
|	README.md
|	CMakeList.txt
|	smoothsurface.cpp
|	microfacet.cpp
|	...
|---scenes
	|	grace.exr
	|	sphere_mf_chrome.xml
	|	sphere_ss_chrome.xml
	|	...
	|---merlmit

Add new BRDF models (based on the assignment description)

1. Copy or write the new BRDF model in the root folder, e.g., smoothsurface.cpp.
2. Add the new BRDF model to CMakeList.txt, e.g., adding the following two lines to CMakeList.txt.

# add a new BRDF model
add_bsdf(smoothsurface smoothsurface.cpp)

3. Run cmake . and make in the root folder to compile the new BRDF model.

Run the new BRDF model

1. Change BRDF parameters by modifying the *.xml file in the ~/scenes folder.

• Change the BRDF model and type of the xml file. For example,

  <bsdf type="smoothsurvace" id="alum-bronze-smooth-surface">
  ...
  </bsdf>
  <shape type="sphere">
  <float name="radius" value="1"/>
  <ref id="alum-bronze-smooth-surface"/>
  </shape>

• Set the BRDF parameters. Low et al
  • m_difusseReflectance: diffuse factor, RGB values.
  • m_A: A for the S function, RGB values.
  • m_B: B for the S function, float value.
  • m_C: C for the S function, float value.
  • m_F0: Fresnel factor, float value.

2. Change other settings if necessary. For example, change the angle of the view direction to -225.

-<transform name="toWorld">
<rotate y="1" angle="-225"/>
</transform>

3. Run the code in the root folder

./binaries/mitsuba ./scenes/sphere_XX_YYY.xml

XX represnets mf (Microfacet) or sf (Smooth Surface), and YYY is the name of the material, e.g., chrome or alum_bronze. The result of sphere_XX_YYY.exr will be in the folder ./scenes after about 30 seconds or 1 minute.