## 4 Development
### Solution
#### 4.2.3 Bim  
Once both the infrastructure and the dynamic construction element had been defined, the next step was to apply BIM to carry out the simulation of the project. For this reason, a study of the various available software alternatives on the market (Autodesk, Bentley and Rhinoceros 3D) was previously analysed. The 3D geometries to be modelled were complex and had to be animated in order to represent the transition from folded to unfolded position. Another basic requirement was that any desired aspect could be easily modified once the model was finished. Among all the possible options, the software chosen was Rhinoceros  
Figure 5: Solar path by season. 3D, with Grasshopper for the parametric modelling of both the origami element and the building, and V-ray for the project image rendering. * Origami element modelling  
The aim was to parameterise the geometry. For this purpose, the software Grasshopper was used. Figure 6 shows the process followed. The BIM element to be modelled is considered as \"IfcShadingDevice\", according to IFC Standards. The complete inheritance of it is \"ifcRoot\" > \"IfcObjectDefinition\" > \"IfcProduct\" > \"IfcElement\" > \"IfcBuildingElement\" and \"IfcShadingDevice\". The first step was to draw the plane that l contained the base of the piece, which is the initial square. A base of three metres by three metres was made, as detailed in the definition of the origami element. In addition, a repetition function was prepared in both the X and Y axis (both coinciding with the plane of the facade), so that when the whole piece was modelled, it was possible to repeat it. Subsequently, three dynamic parameters were added. They were associated with an outer square (like the initial one) and an inner square rotated 90\({}^{\circ}\) with respect to the previous one, which can be identified as the \"inner square\". The outer square is shown in green at point 2 in Figure 6, while the rhombus is shown in green at point 3 in Figure 6. Dimension _al_ was the distance from the centre of the squares to the vertex of the outer square. The distance \"b\" is the one between the centre of all squares and the vertices of the inner square. The distance between the XY plane and the furthest point of the XY plane is set as \(h\). Once the three dynamic distances have been identified, the complete structure was created. To do this, the different points of the initial square, the outer square, the inner square and the height were joined together, as detailed in point 5 of Figure 6. Once all the points had been joined together, the surface is created that gives rise to the final origami figure. An example of how the parameterisation of this geometry works is shown in Figure 7, where the entire arrangement of points is modified according to a single value, the height \(h\). Figure 6: BIM origami element modelling. This fully parameterised origami element was replicated along the two fictitious facades. The origami elements were cloned along the X and Y axes. The elements of each facade created a panel in the XY plane. From this panel, a point of X and Y coordinates was created, which simulated the position of the sun. Depending on this point, the heights of the origami elements (4 th point of Figure 6) vary between 0 and 1. In this way, the elements had different degrees of openness depending on this point, as it is detailed in Figure 7. The location of all the elements on the facade and the different degree of openness depending on the sun can be seen in Figure 8.  
Figure 7: Parameterization of origami figure by height. * Generic building modelling  
As indicated above, an octahedral geometry with only three parametric distances was chosen: the diagonal of the base square and the sides of the square. This enabled modifying the facade areas quickly and easily. A common distance between floors of three metres and a distance between columns of six metres were considered. The modelling was done with the same tool used for the origami element modelling, the Grasshopper software.