## 2 The Current State of 3D Repositories Quantified  
Various studies have been conducted to date on 3D heritage data (see Table 2). The literature-based reviews and surveys by FSU Jena [21; 22], by the Virtual Multimodal Museum CSA [22], and the VIGIE study on the 3D digitization of tangible heritage examinedusage scenarios and defined quality criteria [23]. Specific studies on 3D infrastructures include the Dutch Pure3D (2021: 48 valid responses) [24], the Europeana 3D (2019: 38 individuals) [25], the EU INCEPTION project survey [26], and the survey by the US CS3 DP group [27] (2018: 53 respondents). Most recently, the UK 3D Data Service Survey [28] was conducted in 2022. In addition, several surveys on available platforms, repositories, and frameworks were compiled recently [30; 31; 32; 33; 34] to provide an overview of particular technologies such as laser scanning [35], photogrammetry [36], machine learning [37], and extended reality technologies [38]. Moreover, several studies analyze data and digitization within specific domains with occasional links to 3D data. These include the ARIADNE+ user survey [39] for archaeology, the ICOM surveys [40; 41; 42], and the survey by [PERSON] et al. [43] analyzing museums during the COVID-19 pandemic. \begin{table}
\begin{tabular}{l l l} \hline
**Repository** & **Number of 3D Models Contained** \\ \hline Sketchfab (objects tagged “cultural heritage”) & 100,000+ (10/2019) [17] \\ \hline Europeana & 5931 (5/2023) [18] \\ \hline Kompakkt & 261 (4/2023) [19] \\ \hline DFG 3D Viewer & 3922 (4/2023) [20] \\ \hline \end{tabular}
\end{table} 
Table 1: The number of 3D models stored in repositories (examples). \begin{table}
\begin{tabular}{l l l l} \hline
**Year** & **Study** & **Scope** & **Participant No.** \\ \hline
2013 & Conference article review & & \\  & (2000–2013) [22] & Worldwide & 478 published articles \\ \hline
2016 & FSU Jena author survey [21] & Worldwide & 988 participants \\ \hline
2017 & ViMM survey [22] & Worldwide & 782 responses \\ \hline
2016 & INCEPTION survey [26] & EU & 53 representatives \\ \hline
2018 & CS3 DP [27] & US & 53 respondents \\ \hline
2019 & Europeana 3D Survey [25] & EU & 38 individuals \\ \hline
2020 & VIGIE Study [23] & Worldwide & 420 respondents \\ \hline
2021 & Pure3D [29] & NL & 48 responses \\ \hline
2022 & UK 3D Data Service Survey [28] & UK & Unknown \\ \hline \end{tabular}
\end{table} 
Table 2: Surveys related to 3D heritage modeling. Community and 3D objects. The large-scale surveys by FSU Jena [21], ViMM [22], and EU VIGIE [23] provided a comprehensive analysis of a community, as well as objects and technologies for 3D modeling. Most humanities and cultural science actors come specifically from archaeology, art history, architectural history, and historical sciences (see Figure 1). Additionally, there is the involvement of actors from academia, heritage institutions, and commercial companies. Objects are primarily monuments or architectural objects, followed by sculptural art objects (Figure 2). With regard to modeling technologies in current surveys, specifically photogrammetry or scans of existing objects are used (see Figure 3). Hand-modeled 3D reconstructions are rarely explicitly mentioned, but according to our previous studies [46], these account for approx. 20% of the models. Formats and requirements for 3D viewer repositories were collected through multiple surveys on a national level and also by the Europeana survey on a pan-national level. In general, it can be observed that a wide variety of data formats are used, with OBJ being particularly relevant, but also gITF and COLLADA (see Figure 4). Models are predominantly viewed on laptops, while tablets and smartphones are significant, albeit to a lesser extent [24]. Figure 1: Users of 3D heritage data. (**a**) Participating disciplines, FSU Author survey (Figure [22]). (**b**) Project—disciplines, PURE 3D Survey 2020 (Figure: [29]). (**c**) Disciplines of respondents, VIGIE Survey 2021 (Figure: [23]). (**d**) Disciplines of article authors and co-authors, Conf.