Fourth step

Optionally, if the difference between the temperatures of two consecutive depth levels is less than 3 ◦C, some of the consecutive depth levels are clustered together. In other words, some objects from different depth levels are put into a similar intermediate depth level. This helps the user recognizing the different depth levels better by decreasing the total different temperatures to be felt and recognized.

Following these four steps creates a simple mapping that does not consider the absolute distance between depth levels (except for the nearest and farthest depth levels, whose relatively absolute distance is considered for choosing the initial temperature range), but only the number of depth levels and the order in which they approach the user. More complex mappings could be designed, such as a mapping which took into consideration the absolute depth levels of all the features. However, this simple mapping is enough for conveying the different depth levels through temperature cues to give an idea to the VIP of where the different features of the artwork are placed according to depth.

Next, this temperature-depth mapping will be applied and examples of its use will be given in two different types of applications: for representing depth of the different objects of a bi-dimensional artwork and for representing color-based depth of a bi-dimensional image (an effect called chromostereopsis).

### 2.2.1. Application 1: Artwork Depth

The temperature-depth mapping can be used to convey through temperature the different depth levels of the objects of an artwork. In that way, the visually impaired user can sense more deeply the depth presented in a painting.

In this case, different temperatures for the objects that are at different levels of depth are assigned by following the method presented above.

Before applying the method, first, some techniques used by artists for creating the illusion of depth in visual arts will be contemplated and the method applied to those simple cases. After that, some examples of the temperature-depth mapping method presented above will be applied to two real famous artworks.

### *Illusion of depth in 2D visual arts*

In 2D visual arts, there are many ways of creating the illusion of depth, such as:


The most relevant ones are layering and overlapping, shading, and size, placement and perspective. However, color, hue, and value can also contribute to create strong feelings of depth, an e ffect called chromostereopsis [2]. This e ffect will be explored separately in the following section. First, shading and size, placement and perspective techniques will be explained (since layering and overlapping is a really intuitive and common technique, no explanation will be given).
