*Examples*

In this painting, by Matisse (Figure 8), there are seven different elements, which can be seen in Table 8. The dancers have been numbered to aid identification. By looking at the drawing, sighted people can generally agree on five different levels of depth, these levels of depth have been linked to the different depth layers from 1 to 5, with 1 being the nearest layer and 5 being the farthest depth layer from the viewers' location as a reference. Nearer depth layered elements need to have higher temperatures so temperatures are assigned to the extreme layers (38 ◦C for the Dancer 5 ◦C and 14 ◦C for Sky) and then that temperature range is divided by five (since we have five depth layers). The reason for choosing 38 ◦C and 14 ◦C was because Sky and Dancer 5 are visually really far away from each other, so the temperature for those extreme depth layers were chosen in a way that the temperature difference was maximum: the lowest and highest temperatures from the defined [14 ◦C, 38 ◦C] temperature range in which we are working. The resulting temperatures are linked to their respective layers and they can all be seen in Table 10.

**Figure 8.** *Dance II* by Henri Matisse, 1910 (Hermitage Museum, Saint Petersburg, Russia).


**Table 10.** Temperature-depth mapping of Matisse's "*The Dance*".

In the case of "*Starry Night*" (Figure 9) by Van Gogh, there are many depth layers, as can be seen in Table 11. As before, these depth layers are selected in a visual way, by contemplating the artwork and choosing the main depth levels defined by the features. In our case, nine depth layers were defined. However, since such a high number of layers would force the user to feel and di fferentiate many di fferent temperatures, we decided to simplify the number of depth layers. For that, elements were visually and conceptually grouped to check whether some of the elements from di fferent depth levels could be grouped under a common depth level. As a result, the starts and the moon, and the mountain and the forest (both pairs of elements having both conceptual common traits and being visually near to each other) were grouped together in two common depth levels. This can be seen in Table 11 where Forest and Mountains share depth layer number 3, and Stars and Moon share the layer number 4. In this way, the number of temperatures is less and the user can identify the di fferent temperatures and depth layers in an easier way. Therefore, even though technically the forest and the mountains are not in the same depth level, we can simplify it to aid identification. In general, this technique should be performed when the temperature di fference between layers becomes less than 3 ◦C.

**Figure 9.** *The Starry Night* by Vincent Van Gogh, 1889 (Museum of Modern Art, New York City).


**Table 11.** Temperature-depth mapping of Van Gogh's "*Starry Night*".

### 2.2.2. Application 2: Chromostereopsis

Another possible application of the temperature-depth algorithm is for conveying the e ffect of chromostereopsis through temperature. Chromostereopsis [2] is the e ffect produced by colors on a flat two-dimensional surface by which each color seems to be located in di fferent depth planes, in spite of the two-dimensionality of the image [19]. It is important not to mistake this e ffect with the association made by artists between red colors and blue colors as advancing and receding colors, since that idea might be based on the brightness produced by atmospheric haze, which is associated with distance, rather than with the e ffect of chromostereopsis [20]. Chromostereopsis is produced by an e ffect called chromatic aberration, which is the result from the di fferential refraction of light depending on its wavelength, causing some light rays to converge before others in the eye and/or to be located on non-corresponding locations of the two eyes during binocular viewing.

Next, an exploratory analysis of the main features that make a color seem farther or nearer will be given, followed by a simple algorithm for conveying chromostereoptic depth by means of temperature. However, first, a brief explanation about colors needs to be given.
