# AR in the Architecture Domain: State of the Art
## 6 AR Development Tools  
Augmented reality software development kits (AR-SDKs) have a \"bridge\" function between the device and the virtual content through a platform devoted to data integration, management, and visualization. Each one offers a specific GUI (graphical user interface) to connect the user's virtual content. These are intended as \"interaction metaphors\" between the input and output data, highlighting the communicative capacities and purposes of AR digital content in the real world. Several parameters define the use of these AR-SDKs, and their possible application in the architecture domain: cost, supported platform, image or target recognition, 3D and tracking, support by game engines, cloud or local databases, geolocation, and SLAM [143]. Moreover, in this paragraph, a different clustering of AR-SDKs based on accessibility and availability is proposed, dividing them into open-source, free (proprietary), and paid (commercial) (Figure 13). The other specific AR-SDK characteristics will be evaluated accordingly. The open-source systems guarantee their implementation through access to the source code. In contrast, the others differ only in terms of being free or paid, but do not allow a system modification.  
Most of the leading AR-SDKs were developed between 2007 and 2012, but the app scenario has profoundly changed after 10 years. The number of platforms available on the market has increased significantly. Here, the main multipurpose platforms, or those devoted to the architecture domain, are discussed (Table 2).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**SDK** & **Typology** & **Platform** & **Tracking** & **Domain** \\ \hline ARToolkit & GPL 1 & Multiplatform & Marker & Generic \\ DroidAR & GPL & Android & Location/Marker & Generic \\ AR.js & GPL & Multiplatform & Location/Marker & Generic \\ EasyAR Sense & GPL/Commercial & Android & Marker/Markerless & Generic \\ Apple ARKit & Free/Proprietary & iOS & Location/Markerless & Generic \\ Google ARCore & Free/Proprietary & Android & Location/Markerless & Generic \\ ARIopoa & Free/Proprietary & Multiplatform & Location/Marker/Markerless & Graphic \\ Archi-Lens & Free/Proprietary & Multiplatform & Marker & AEC/Design \\ Layar & Commercial & Multiplatform & Location/Marker/Markerless & Generic \\ Wikytude & Free/Commercial & Multiplatform & Location/Marker/Markerless & Generic \\ Vuforia & Free/Commercial & Multiplatform & Location/Marker/Markerless & Generic \\ MAXST & Commercial & Multiplatform & Marker/Markerless & Generic \\ AkulAR & Free/Commercial & Multiplatform & Location/Marker & Architecture \\ Augment & Commercial & Multiplatform & Marker/Markerless & eCommerce/AEC \\ ARKi & Free/Commercial & IOS (Android soon) & Location/Markerless & AEC \\ Fuzor & Commercial & Windows & Markerless & AEC \\ GammaAR & Commercial & Multiplatform & Markerless & AEC \\ Dalux TwinBIM & Commercial & Multiplatform & Markerless & AEC \\ Fologgram & Commercial & Multiplatform & Marker & Generic \\ \hline \hline \end{tabular}  
* General public license.  
\end{table}
Table 2: List of SDKs and relative characteristics.  
Figure 13: Block diagram of the main features of the AR-SDKs.