"Printed Perforated Lampshades for Continuous Projective Images" , which is accepted to Transactions on Graphics, has been invited to present on ACM SIGGRAPH 2016. In this paper, we present a technique for designing 3D-printed perforated lampshades that project continuous grayscale images onto the surrounding walls. Given the geometry of the lampshade and a target grayscale image, our method computes a distribution of tiny holes over the shell, such that the combined footprints of the light emanating through the holes form the target image on a nearby diffuse surface. Our objective is to approximate the continuous tones and the spatial detail of the target image, to the extent possible within the constraints of the fabrication process.
To ensure structural integrity, there are lower bounds on the thickness of the shell, the radii of the holes, and the minimal distances between adjacent holes. Thus, the holes are realized as thin tubes distributed over the lampshade surface. The amount of light passing through a single tube may be controlled by the tube's radius and by its orientation (tilt angle). The core of our technique thus consists of determining a suitable configuration of the tubes: their distribution across the relevant portion of the lampshade, as well as the parameters (radius, tilt angle) of each tube. This is achieved by computing a capacity-constrained Voronoi tessellation over a suitably defined density function, and embedding a tube inside the maximal inscribed circle of each tessellation cell.
"Connected Fermat Spirals for Layered Fabrication" was conditionally accepted to ACM SIGGRAPH 2016. In this paper, we develop a new kind of "space-filling" curves, connected Fermat spirals, and show their advantages as a tool path fill pattern for layered fabrication. Unlike classical space-filling curves such as the Peano or Hilbert curves, which constantly wind and bind to preserve locality, connected Fermat spirals are formed mostly by long, low-curvature paths. This geometric property, along with continuity, greatly influences the quality and efficiency of layered fabrication. Given a connected 2D region, we first decompose it into a set of sub-regions, each of which can be filled with a single continuous Fermat spiral. We show that it is always possible to start and end a Fermat spiral fill at approximately the same location on the outer boundary of the filled region. This special property allows the Fermat spiral fills to be joined systematically along a graph traversal of the decomposed sub-regions. The result is a globally continuous curve. We demonstrate that printing 2D layers following tool paths as connected Fermat spirals leads to efficient and quality fabrication, compared to conventional fill patterns.
国际计算机协会ACM举办的SIGGRAPH国际图形学年会是世界上规模最大、影响最广、最权威的一个集科学、艺术、商业于一身的前沿图形技术展示与学术研讨会。历年大会都有丰富的成果展示，绝大部分计算机图形技术软硬件厂商及游戏与影视动漫创作者每年都会在SIGGRAPH年会上发布最新产品或艺术作品。因此，SIGGRAPH在推动图形技术，特别是3D技术的快速发展方面都有着相当的影响力，堪称图形学领域的奥斯卡。
