The exterior form of the Museo Soumaya is double-curved surface. The different floors respond to the collection, thus expanding and contracting. The design surface was defined early in the design process by scanning a physical model. This scan created a digital model of the design surface which allowed the structure to be designed to fit with this surface. The structure was composed of twenty-six curving columns connected to horizontal steel rings designed with ARUP. Both the columns and the rings lie on the design surface of the building. The design intent was for the envelope to be composed of hexagonal aluminum panels. However, the challenge was that the structure was already being assembled so there was very little room for modifications or rationalization to the surface and the panels. A Gaussian analysis was done on the design surface to identify the areas with the most curvature. The design intent was to have a consistent gap between all of the panels on the surface. The geometric solution was to stretch each hexagon panel to maintain the spacing. Each hexagon panel responds in its size and angles to the local geometry of the surface. This resulted in 16,000 unique hexagonal panels. Between the interior surface and exterior hexagonal panels is a complex three-dimensional structure. This structure did not contain a single repeating strut. Every element in this structure is adapted to the local surface conditions and was fabricated off-site in Monterrey, Mexico. Elements within this structure needed to have a precision of five inches. The secondary structure was developed by Geometrica, a designer/fabricator of very large structures using their own 3d modeling software and digital information for fabrication. For the panels the Gehry Technologies team created the shop drawings from the Digital Project Model using programming to extract every single panel into a 2d drawing to be dimensioned and printed for the fabricators. More than 14,000 shop drawings where created.