PBC - Porosity by Curvature

PBC – Porosity by Curvature is a research exploration about the relations between porosity and structural efficiency depending on surface curvature, carried at the University of Bologna, Faculty of Engineering, through the SiLaB (modeling and visual representation lab), with the help of the technician Giovanni Bacci. Folds in surfaces are topological conditions that define differences and endow them with several performative qualities: structural efficiency couples with an increase in surface area comprised in a single volume unit, thus raising the possibilities of energy-matter exchange. This is a common feature in nature for organisms whose metabolism is a dissipative one while needing a relatively smaller body mass (and thus volume) for movement and self maintenance. Speaking in terms of architecture this means light, radiation, heat, air, sound exchange between an exterior and an interior space determined by the membrane itself. Porosity is the condition by which the aforementioned exchanges take place. How can these conditions (porosity and structural efficiency) be related together through geometric intrinsic properties in a multi-performance membrane? Surface sampling and discretization are compulsory steps in this process; the chosen strategy is to perform them through tessellation. Tessellation is a strategy that makes use of geometry and discretization algorithms in order to establish parametric part-to-whole and whole-to-part relationships; it can also prove to be a key parameter to describe curvature in an useful way in which hierarchic connections between porosity and structure work as its derived conditions. Starting from a generic double curvature NURBS surface, tessellation algorithms try to approximate the surface with the use of planar faces, generating a thicker mesh in smaller curvature areas, while acting the other way around in flatter zones. The mesh thickening describes and discretizes at once curvature variation along the surface, providing the points needed for tessellation. Openings are created according to a percentage of the distance between a point and his neighbors, thus linking algorithmically curvature (which is an intrinsic property of the surface) and porosity. This local rule brings to the formation of emergent surface effects, such as morphological differentiation from wider spans in flatter areas to dense ribs in smaller curvature ones. These differentiations endow those areas with different structural properties which, even though geometry-related, need to be investigated both in physical prototypes and virtual models. Model was created in Autodesk® Maya: from a generic, double curvature NURBS surface several meshing algorithms and parameters combination were tested; the chosen generation was then exported directly in STL format and prototyped by Z-Corp® 3D printer. 3D prototype is also a useful model to test structural performance in order to have the necessary feedback for the next research phase more focused on structural related properties (research in progress).