# Content Adaptation and Depth Perception
## 7 Discussion  
SliceView suffers from some of the same problems exposed by Pepper's Cone [18], such as not being suitable for bright outdoor environments, and ambient light reducing contrast and the perceived image quality due to the highlighted dust, scratches and imperfections on the projection surfaces. However, a regular LCD monitor is bright enough to offer an acceptable experience. Dark areas behind the display provide the best viewing conditions, therefore, we suggest enclosing SliceView inside a dark cardboard box (see Figure 17). Bright contrasted images are, in general, better suited to SliceView, whilst dark colors should only be used on backgrounds or unimportant areas. White cannot be fully blocked by other layers, therefore, full opacity on a layer is not achievable and light emitted from aligned pixels at different depths is perceived cumulatively. A dark foreground in front of a bright background is almost invisible one solution is masking the foreground silhouette in black on the background layer. This considerably improves the final image quality, but leaves gaps when the display is not directly observed from the front. We consider that interesting color-mixing can be achieved by exploiting this to provide an ethereal effect. Figure 16: User interacting with a 3D scene sliced into three layers. Figure 17: (**a**) SliceView on a completely dark environment, (**b**) under a regular household light bulb, and (**c**) under an LED spotlight. Layer thickness has a critical role in image quality. (See Figures 4 and 5). When using sheets of more than 1-mm thickness, there are perceivable double reflections, and text is difficult to read when using sheets thicker than 2 mm. Double reflections also produce less sharp images. When using thinner sheets, the lack of rigidity results in wobbly artefacts and the assembly of SliceView is more complicated. The use of more rigid and reflective materials, such as tempered glass or silica glass, could avoid these problems, but these materials may be harder to obtain and increase the cost. SliceView does not provide a 360\({}^{\circ}\) field of view; the comfortable field of view is approximately 90\({}^{\circ}\). It would be possible to obtain a 360\({}^{\circ}\) FOV by using multiple concentric cones, i.e., mixing Pepper's cone [18] and SliceView concepts. However, back reflections from the opposite sections and reduced spatial resolution would reduce image quality significantly. Despite being easy to build, SliceView is not plug&play, some basic calibration is needed after assembling it. As shown in Figure 3, transformations and sheet angle tuning are required to obtain optimal results. To ease this process, calibration templates are provided. Adding more layers to increase depth resolution reduces planar resolution, because the same screen is used to project light onto each layer. However, we reckon that with monitors increasing in resolution (1080 p, 4 K and so on), using more than five layers is feasible. Increasing the size of SliceView can be limited by the size of the monitor. TV or PC monitor screens are available in larger sizes but at an increased price. Projector technologies may be more suited for a large-scale SliceView. Like most projection-based displays, SliceView also exhibits the cardboard effect [21]. This can be slightly reduced by increasing the number of layers, at the cost of losing planar resolution. Most of our proposed applications do not avoid, but take advantage of, this effect. When using a low number of layers, empty spaces are available between them, in which we could place real objects to be mixed with the virtual scene in a diorama-like style, something unachievable on the LookingGlass or Pepper's Cone alternatives. Touch sensors could also be placed at or between different layers to provide some kind of direct interaction. Nevertheless, as each layer is completely solid, they could be only reached through the top or sides. This is not possible when using a black box enclosing the display to increase perceived brightness.