Extension of the ABTF material acquisition and rendering process to CultArc3D image data
The importance of photorealistic 3D rendering of different materials is increasing, as there are various domains of application, such as the textile and the 3D games industry. In order to be able to do real-time rendering involving a physical material, a method for its acquisition and realistic rendering on 3D geometry is required. So far a single-camera system called ABTF Scanner is already able to acquire flat materials that are anisotropic (appearance dependent on rotation around surface normal) using a turntable, which makes it possible to map the acquired material onto an arbitrary 3D geometry during real-time rendering. Another scanner system consisting of multiple cameras called CultArc3D can also be used for this purpose. Due to its structure, allowing for lighting over a hemisphere by turning an arc equipped with light sources, there is no need for a turntable to acquire materials, as opposed to the single-camera system that achieves hemispheric illumination by combining a fixed quarter light arc with a rotary. In order to make images acquired by CultArc3D usable for real-time rendering, this thesis extends the software implemented for the ABTF Scanner. The extension was done in a way that makes the software multi functional in that it is now able to do real-time rendering for materials acquired by either of the above mentioned scanner system. For the first time images taken by CultArc3D can be used for renderings of ABTF material samples that capture material behavior for a comparable set of virtual light directions. Additionally a new shader (computer program used for 3D rendering) is implemented to provide real-time rendering with respect to the different data structure imposed by the concept of CultArc3D. The experimental evaluation shows that real-time rendering with the images acquired by CultArc3D can lead to better results compared to images taken by the ABTF Scanner, because the back-rotation of images, introduced by the rotary in the ABTF Scanner setup, is not required by CultArc3D. Thus, a number of calibrations and alignment steps that possibly introduce visual artifacts if not performed correctly, can be avoided. As a result CultArc3D can now be used for ABTF real-time rendering in addition to its capability of acquiring geometry, texture and a number of different optical material models. The software can be extended for different viewing perspectives during rendering in future work, due a hemispherical distribution of camera perspectives around the object.
Darmstadt, Hochschule, Bachelor Thesis, 2018