The third option of the user is a quiz game, implemented in the 3D space of the interior ground floor columnar hall of the
Stoa of Attalos, where the player can freely navigate.
Ten interaction hotspots trigger a GUI quiz dialog whenever the player approaches one of them. In all cases, the question concerns the originality of the specific part which is adequately highlighted for clarity.
Each correct answer is awarded with one point.
The answers are accompanied with context-sensitive information.
Since the gaming concept in this case is highly dependent on the fidelity of the virtual representation of the interior of the Stoa of Attalos, the method selected for the generation of the 3D model of the virtual space was again image-based modelling technique.
The equipment used for the collection of data were the Canon EOS 1Ds, MK III full frame DSLR camera in combination with the Canon EF 50mm f/1.2 USM L lens and the Pentax K-5 DSLR camera paired with the Pentax SMC DA 18-55mm f/3.5-5.6 AL WR lens and a CMOS 15.7 x 23.7 mm sensor.
The challenge of building a model for the specific application was to reconstruct the interior of the Stoa of Attalos as a continuous 3D space. That fact alone meant that a great number of pictures had to be captured. Special strategy had to be devised in order to keep the number of images low.
The dense point cloud generated in PhotoScan, was exported as a .txt file and then imported in Geomagic Studio. for cleaning, for removing noise and resampling the points and also wrapping the points to meshes [16]. The meshes were decimated, in order to result in manageable files.
The final model of the internal façade of the southern wall (Fig.6) was produced from 679 images and had 2.903.381 polygon faces,
which was a very large file for Unity to handle.
A series of geometry simplification methods were tested in order to achieve a significantly lighter model.
Retopology[17] approaches were considered as more efficient and the freely-available Autodesk Meshmixer 3.0 was selected.
The specific software is a mesh editing, procedural retopology tool, strongly focused on 3D printing [18].
Meshmixer can alter the number of mesh triangles or the mesh itself as a sculpting tool.
Most importantly it keeps the UV connection intact, therefore allowing the preservation of the model's original texture.
The resulting model has a smaller number of polygons, but maintains a highly detailed texture map.
Thus, it is more suitable for real-time rendering applications such as game engines.
After simplifying the model with Meshmixer, the count of the polygon faces was reduced to 1.026.335 and was easily imported to Unity.
Colliders were set up for emulating physical objects as barriers in the player’s movement.
Interaction of the player with the ten hotspots was essentially developed as the interaction between two game objects. Firstly a child object of the First Person Character called Trigger Camera, a rectangular and oblong collider marked as a trigger and secondly the objects Real and Fake Triggers, also box colliders marked as triggers, which correspond to structure areas that are part of the quiz game.
The interaction between the two triggers activates a series of game mechanisms and the area in question is highlighted.
If the area is part of a wall, a child object, i.e. a stressed red outline of the area in question, is activated and additionally a GUI quiz dialog appears with the question, the answer and the additional info (Fig. 7).
A series of standard and custom scripts, written in C# programming language govern the relations between actions and events following the gameplay described.