Tag: shadow

In the last part of the short blog series, we will take a quick look at the required realism of shadow in Augmented Reality scenarios. Is shadow detail crucial for user acceptance?

Read part 1 for an introduction and how shadow influences the estimation of height, and part 2 for more on estimation of depth and light position.

Required Detail of Shadows

The HoloLens is essentially a head-worn, battery-powered PC. As such, the computing capacity is of course much less compared to most virtual reality systems like the HTC Vive or Oculus Rift where a full-blown PC with a power consumption of around 600 W is rendering the scenes.

Many games use highly simplified shadows that are only a very crude approximation of what a real shadow should look like. In this experiment, the aim was to examine how much simplification of volumentric shadows is accepted by subjects.

The scenario consisted of a high quality torus that floated above the floor. The shadow was generated using different levels of detail; the highest had no visible edges, while the lowest was basically just a pentagon.

In the previous blog post of this short series, I described the findings of my study Benefits and Parameters of Shadow in Augmented Reality-Environments on how shadow influences the perception of height (distance to the floor) in Augmented Reality environments. Before we get to a possible solution for Mixed Reality Scenarios with Microsoft HoloLens, let’s take a look at more interesting results of the study.

Estimation of Depth

To correctly percieve a mixed reality scene, the user also has to judge the depth (distance to the camera) of a virtual 3D object in a real scene. If the perception is off, it can destroy the mixed reality effect. In some applications where accuracy is vital, wrong perception of depth can have even more severe implications.

During this experiment, participants of the study were presented with two spheres that varied in size and depth. In random order, every scene was presented twice – once with shadows present, once without shadows.

Usually, holograms placed in real environments through Microsoft HoloLens do not have a shadow. This is mainly due to technical reasons of the HoloLens display, as I’ll discuss in a later blog post.

However, for the scene perception and to correctly determine the holographic object position in the real-world 3D space, as well as for the “feeling” that the scene looks real, shadow is of tremendous importance.

Study on Shadow in Augmented Reality

To get exact numbers and to better understand the situation, I’ve written my Bachelor Thesis “Benefits and Parameters of Shadow in Augmented Reality-Environments” in 2004. Even though back then the study was done with marker-based Augmented Reality, the general setting is comparable to scenes created with HoloLens.

Using an experimental approach, 23 participants were tasked with conducting tests and filling out a questionnaire, judging different AR situations. The tool to create the AR scenes was ShadowAReality by Stephan Drab et. al.

Why Shadow is Important for AR

Literature research showed that shadows are of significant importance for realistic perception. They allow a correct estimation of the placement of objects in the virtual direction, as well as the distance to the camera. Furthermore, shadow defines the volume of the object. Overall, shadows contain a big amount of additional information, which obviously lacks if shadows are missing. They play an important role in how realistic a scene looks.