# Mixed Reality: A Reconsideration Based on Mixed Objects and Geospatial Modalities
## 4 MR Demonstration: Mixed Objects and Geospatial Modalities
### Contribution and Innovative Features  
The innovation of the study presented in this article relates to the inclusion of geoinformatics and most importantly Geospatial Linking Modalities, which in turn enable the rendering of features of the environment, such as historical buildings, as Mixed Objects. This enhances the MR experience significantly by allowing new interaction affordances of real and virtual objects (such as mutual occlusion of moving objects in real-time). The use of geoinformatics allows the visualization of e.g., early construction phases of a heritage building [6] as the 3D modelling of the existing edifice is merged with that of its appearance in the past. Such projects may already, exist such as [PERSON] et al. [32] in CH, but the inclusion of the Mixed Object principle is not developed in these existing instances, delimiting the scope of the MR application that does not allow e.g., Cultural Heritage (CH) buildings (as mixed objects) to interact with virtual objects. The integration of mixed object capabilities is an innovative feature that does not exist hitherto in CH-related research projects such as those carefully categorized in the recent and extensive survey of [PERSON] et al. [33]. Likewise, in [34] the articles presented within Part 4 addressing MR efforts in CH that closely relate to geospatial data (under the title \"Geospatial\") often incorporate innovative approaches such as e.g., the concept of 5D modelling [35] that enables visualization of consequent construction phases of a historical church. Nevertheless, they do not incorporate the geospatial modalities present in this study that allow for the full exploitation of the mixed object concept. In instances such as in Reitmayr and Schmalstieg [36], although static virtual objects (pathway 3D/2D markers) interact with the built environment in CH sites, the modelled buildings are not accurately mapped, nor can previous states (e.g., initial monument condition) be overlaid. Moreover, the application cannot accommodate dynamic/moving virtual objects, such as virtual crowds interacting with buildings rendered as mixed objects (i.e., by means of occlusion). In the same vein, all the instances of pertinent research that are referred to within this article do not integrate a comprehensive Geospatial Linking Modalities framework that allows real-time interactions between environmental features rendered as mixed objects, virtual and actual objects, and actors. This article draws heavily from previous research such as that conducted by [PERSON] and [PERSON] [7] and previous work in the field that provides a framework for the key term Mixed Object and pertinent linking modalities. However, these instances of practice that provide the basis for this research did not migrate geoinformatics in an MR model in a way that combines both multilayered and accurate visualization and real-time interaction between actual, mixed, and virtual objects (perhaps due to the technological constraints). This integrated and comprehensive use of Geospatial Linking Modalities and mixed objects proper in an MR ecosystem described in scheme 6 is the innovation this article presents. Last but not least, since the 2010s, augmented reality with the use of geospatial technologies for e.g., 3D building features' tracking [37; 38] has proliferated in sectors such as construction and environmental tracking [39], but Geospatial Linking Modalities in these applications are not orientated towards providing an MR experience of the past states, or the full and real-time interaction of mapped/mixed objects fusing real and virtual worlds to the extent needed to bring the past into life through activated spectatorship and visitor engagement through a user-friendly interface that is addressed not to experts/professionals but to people who wish to savor the experience of merging a site's past spatial and temporal frameworks under a new MR model. Occlusions or interpositions between real and virtual objects constitute one of the challenges of MR [40].