Abstract
How materials reflect and transmit light is an important area of study for computer graphics, optics, material science, and other industries, but it is difficult to study due to the four-dimensional nature of the elevation and azimuth of incoming light and elevation and azimuth of viewing position.
The purpose of this project is to develop an automated camera system to work in conjunction with a variable illumination sphere in order to photograph various materials being studied from any viewing angle and illuminated from any angle. This will allow researchers to create accurate, physically-based shading models for real-world objects. The camera-control system will also be used for multi-view stereo to capture face models for digital humans as well as real-world objects for computer graphics and animation.
Automating Camera Control for Studying Material Light-Scattering Properties within a Variable Illumination Sphere
Henry Miles, Xiang Li, and Dr. Eric Patterson
Discussion
Methodology
Results
References
A Python-interface of gphoto2 is being used to control the cameras on the light sphere. This program allows control of camera settings including aperture, shutter speed, and ISO, in addition to automating the high-speed capture of images. To use Gphoto2 on Windows, an alternate operating system known as Ubuntu had to be installed so that it would be able to run the program. Using the limited online documentation for Gphoto2, a functional camera control code was created. This control code will allow the cameras to take a rapid series of photographs of an object from many different angles with light also from any angle. This will allow for the creation of detailed 3D virtual models and specular maps of different objects.
This program enables cameras to capture images at high speeds with different angles of light on an object so that the direction of the reflection of the light off the object can be mapped. Currently the code allows the cameras to capture images with specifically set aperture, shutter speed, and ISO.
Currently, the universal stage and its lights work as they are supposed to. The final component of the project is controlling the cameras which this code achieves. The code should allow automation of taking photos and setting aperture, ISO, and shutter speed.
Now that the cameras are programmed properly, the light stage should be functional and can be used for modeling real world objects, creating realistic digital humans (particularly faces), and realistic texture maps for objects like feathers and corroded materials.
Variable-illumination sphere constructed at the Clemson University Zucker Family Graduate Education Center.
A digital model made by capturing images of a sculpted character in the light sphere.
Acknowledgements
This Specular map of a human face displays the direction that light reflects off every point of a surface. Red, yellow, and green each represent an XYZ axis that the light reflects along.