### Architectural versus Analytical Models  
A critical aspect when facilitating close collaboration between architects and engineers is the consideration of model types. The primary purpose of an architectural model is to represent space. On the other side, a structural engineer aims to analyse the strength and stability of the under-laying structure. In an architectural model, all elements such as beams, columns, walls, and roofs generally have a three-dimensional boundary. It is not straightforward to convert these physical elements into elements compatible with an analytical model for finite element analysis. Depending on the problem, different element types may represent the physical situation. Real-world objects are broken down into smaller parts for the analysis, a process known as discretisation. The beam in Figure 3 use used as an example; the architectural beam has a width, depth, and length. Depending on the information sought and expected behaviour, the engineer may use a one-dimensional element such as a beam and bar element consisting of two end nodes connecting a straight line; each end node has degrees of freedom relevant to the problem. In other cases, a two-dimensional model may be more apt. Here the engineer discrerises the beam into shell or plate elements. Apart from the type of element selected, the number of elements used will affect the accuracy of the solution. Finally, solid three-dimensional elements can be used as well. Here, all three dimensions represent the physical beam by \"populating\" it with discrete elements. In most engineering problems related to architecture, one- and two-dimensional elements are sufficiently accurate and computationally effective. In Grasshopper 3D, there are also plugins for FEA internally or connecting to external FEA software such as Karamba3D, Sofistik(r) and FEM-Design(r), respectively. These plugins take line- and surface geometries together with information about cross-sections and material as input for creating structural elements for the analytical model. However, in cases such as the one in this paper where small physical elements, the gridshell nodes, are subjected to sizeable forces, the assumptions necessary for the one- and two-dimensional elements to be valid are no longer applicable. For example, the premise of small deflection and plane sections remaining plane after deformation might not apply in a gridshell node. For these cases, a FEA using solid elements is necessary to evaluate the geometry accurately. Figure 3: The architectural model of a beam represented as 1D, 2D, and 3D analytical elements. This raises the question of how to discretise a volumetric architectural element into small solid finite elements while working in the same software as the architect to maintain close collaboration. Most computer-aided design (CAD) software can easily discretise curves into a series of straight elements or a surface into a mesh of triangular or quad faces. Dividing a volumetric element into a solid mesh element is significantly more complicated. Normally, one would export the object and use different specialised software. As seen for Printshell discussed in Section 2.1, this is a timely procedure which impedes the creativity necessary in a conceptual design phase. Luckily, one of Grasshopper 3D's greatest strengths is the possibility for third-party developers to create their own plugins within the program. The website food4 Rhino.com [15] is a marketplace where these are distributed among users, often free of charge for non-commercial purposes. Here, the plugin Tetrino can be found [16]. This is a plugin working as a wrapper for the TetGen algorithm [17] that allows for the meshing of solid elements directly in Grasshopper 3D. Thus, a change in the architectural model can be automatically updated within Grasshopper 3D for the analytical model of the engineer.