**2. Augmented reality**

Augmented reality is considered as one of the modern technologies that blends virtual objects into the real world. Augmented reality (AR) can be simply defined as a live and integrate direct or indirect view of a physical, real-world environment. It is real-time data that elements are augmented by computer-generated virtual content, for example, sound, video, graphics, or GPS data [7, 8]. Augmented reality is considered as an area in which 3D virtual objects are completely integrated into a 3D real environment in real time. An AR environment supplements the real-world with virtual objects, which are generated by using computer that appear to coexist in the same space as the real world [9]. In another words, augmented reality can be defined as the interactivity of humans with virtual objects that is located in the real environment in order to help the user in executing a task in a physical setting. AR is one of the significant forms of mixed reality (MR), in which real and virtual objects are mixed and showed in a single display in the same time and location as shown in **Figure 1**. Augmented reality seems like fiction because it creates interactive interfaces that specify the delusion that physical and virtual worlds are connected together and that users can physically cross from one to the other [10].

AR does not replace reality, as the virtual reality (VR); it complements real environment with digital information, virtual and computer-generated graphics

**59**

shown in **Figure 3**.

**Figure 2.**

**Figure 3.**

**3. Marker-based augmented reality**

*A user navigating in a virtual environment of VR.*

*Cultural Heritage in Marker-Less Augmented Reality: A Survey*

*A real environment view is augmented with digital information.*

and/or virtual objects as shown in **Figure 2**. However, users navigate in VR by using a computer simulated or imaginary environment called a virtual environment, preventing the real environment. In this environment, all users' senses are controlled using a computer and immersed in a simulated environment [11] as

Marker-based AR uses markers (A two-dimensional pre-defined screen) that are placed in the scene and within the field of vision of the camera in order to help guide the camera pose estimation process [8]. The markers are frequently indicating to as fiducial markers because their position and orientation relative to the scenery are steady. The markers are always planar makers and commonly have powerful feature, for example, long edges, as well as, corners among black and white regions. In this technique, AR puts a powerful emphasis on the design of the marker. One of the most common kinds of marker design is square because the feature of square will allow for accurate localisation of the markers by using its four corner points [12]. Marker-based AR uses computer vision techniques in order to calculate the position and orientation of the camera relative to the marker. The virtual 3D objects can be overlaid accurately on the markers as shown in **Figure 4**. It has a primary operational principle: capture the video input from the camera, add 3D graphics to

the scene and show the augmented frames as a video stream [13].

*DOI: http://dx.doi.org/10.5772/intechopen.80975*

**Figure 1.** *Reality-virtuality continuums [23].*

*Cultural Heritage in Marker-Less Augmented Reality: A Survey DOI: http://dx.doi.org/10.5772/intechopen.80975*

#### **Figure 2.**

*Advanced Methods and New Materials for Cultural Heritage Preservation*

in augmented reality.

**2. Augmented reality**

the output of their device's camera to permit a more natural data presentation compared only using the map alone. Vision-based AR particularly depends on processing the data that is extracted from the images or video frames that have been taken by the device. This kind of AR includes a number of techniques that lend significantly from computer vision to the range, where research progress in AR relies on the progress of the latter [6]. Lately, augmented reality technology has become an accepted technology among scientific community and even public, which is used for merging of real and virtual objects, and mixed it into the real-world environment. However, this technology is used in virtual heritage to improve the visitor experience of a cultural heritage site, as well as, the possibility to present the ancient-ruined building without any damage. In this chapter, we have presented a survey of marker-less AR. This survey is based on the state-of-the-art related to marker-less AR such as indoor marker-less AR, outdoor marker-less AR, real-time solutions to the tracking problem, real-time registration and cultural heritage in AR. Section 3 introduces the marker-based AR and Section 4 is allocated to marker-less AR, while Section 5 presents the researches related to cultural heritage

Section 6 reveals the issues with virtual heritage in augmented reality and Section 7 presents 3D reconstruction techniques for cultural heritage. Section 8 is all about location in AR. The work is concluded by section 9 which is the conclusion.

Augmented reality is considered as one of the modern technologies that blends virtual objects into the real world. Augmented reality (AR) can be simply defined as a live and integrate direct or indirect view of a physical, real-world environment. It is real-time data that elements are augmented by computer-generated virtual content, for example, sound, video, graphics, or GPS data [7, 8]. Augmented reality is considered as an area in which 3D virtual objects are completely integrated into a 3D real environment in real time. An AR environment supplements the real-world with virtual objects, which are generated by using computer that appear to coexist in the same space as the real world [9]. In another words, augmented reality can be defined as the interactivity of humans with virtual objects that is located in the real environment in order to help the user in executing a task in a physical setting. AR is one of the significant forms of mixed reality (MR), in which real and virtual objects are mixed and showed in a single display in the same time and location as shown in **Figure 1**. Augmented reality seems like fiction because it creates interactive interfaces that specify the delusion that physical and virtual worlds are connected

together and that users can physically cross from one to the other [10].

AR does not replace reality, as the virtual reality (VR); it complements real environment with digital information, virtual and computer-generated graphics

**58**

**Figure 1.**

*Reality-virtuality continuums [23].*

*A real environment view is augmented with digital information.*

#### **Figure 3.** *A user navigating in a virtual environment of VR.*

and/or virtual objects as shown in **Figure 2**. However, users navigate in VR by using a computer simulated or imaginary environment called a virtual environment, preventing the real environment. In this environment, all users' senses are controlled using a computer and immersed in a simulated environment [11] as shown in **Figure 3**.
