3D Viewing Devices in Computer Graphics

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We need specialized hardware to represent and view 3D images. 3D viewing devices provide depth perception to users which enhances visual experiences by creating the illusion of three-dimensional spaces. These devices can take many forms like stereoscopes to advanced holographic displays. Read this chapter to learn the basic concepts of 3D viewing devices.

Basics of 3D Viewing Devices

3D displays are capable of conveying depth to the viewer. The most common type of 3D display is stereoscopic displays, which works by showing different images to each eye. This creates a sense of depth. The brain processes these two separate images and merges them to form a three-dimensional effect.

A 3D display can be classified into several categories −

• Stereoscopic displays − These provide a basic 3D effect and are widely used in devices such as virtual reality (VR) headsets.
• Holographic displays − These create a more realistic 3D effect by combining stereoscopic methods with accurate focal lengths. Unlike stereoscopic displays, holographic displays can show a true 3D image that can be visible from different angles.

Some 3D displays also use volumetric methods, to generate content that can be viewed from all angles. This concept was first introduced in 1832 by Sir Charles Wheatstone.

Examples of 3D Viewing Devices

Let us now take a look at some examples of 3D Viewing Devices −

Stereoscopic Displays

We understood there are two types. Let us talk about the examples of a few of them. Stereoscopic displays are the most widely recognized type of 3D viewing device. These displays work by providing each eye with two separate, slightly offset images. The brain combines these images to create a perception of depth.

A common example is the stereoscope, which allows users to view stereographic cards. Each card has two images printed side by side, and when viewed through the stereoscope, the two images merge into one, producing a 3D effect. This basic form of stereoscopic technology is still used in various applications, especially in simple educational tools.

Transparency Viewers

Transparency Viewers work with film-based stereoscopic transparencies. These allows the viewer to see two offset images through a light-transmitting medium. A hand-held viewer that used 35 mm film strips to display stereoscopic images.

In 1939, View-Master took this concept further by miniaturizing the transparency viewers. Using cardboard disks with seven pairs of images, the View-Master allowed users to view 3D images by looking through a hand-held device. This product became immensely popular as a toy and educational tool.

Head-Mounted Displays

Head-mounted displays (HMDs) are advanced 3D devices commonly used for virtual reality experiences. These displays consist of two small screens placed close to the eyes, each showing a different image. By using magnifying lenses, the images are enlarged, and the stereoscopic effect is achieved.

Many modern HMDs come with head-tracking technology, allowing users to "look around" in a virtual world simply by moving their heads. This eliminates the need for external controllers. VR headsets are a great example of head-mounted displays and are popular in gaming, simulations, and virtual tours.

Active Shutter Systems

Active shutter systems, such as LCD shutter glasses, synchronize with the display of a 3D image to create a stereoscopic effect. The glasses contain liquid crystals that alternate between being opaque and transparent in synchronization with the on-screen images, blocking the image from the wrong eye at the right time.

This method is widely used in 3D cinemas and home entertainment systems. Although the glasses are more expensive and require synchronization with the display, they offer a high-quality 3D experience. However, they tend to make images appear dimmer due to the darkening effect caused by the glasses.

Anaglyph 3D

Anaglyph 3D is an older technology that uses colored filters—typically red and cyan—to create a stereoscopic effect. The two images are superimposed with each having a different color filter. When viewed with glasses that have corresponding colored lenses, each eye only sees one image, creating a sense of depth.

While anaglyph 3D glasses are inexpensive and easy to produce, the color reproduction tends to be less accurate than other 3D systems. This method was popular in early 3D movies but has since been replaced by more advanced technologies.

Polarization Systems

Polarization systems are widely used in theatrical 3D displays. In this method, two images are projected through polarizing filters onto the same screen. The viewer wears glasses with polarized lenses that allow each eye to see only one image, creating a stereoscopic effect.

This method, especially with circular polarization, is more effective than linear polarization. Circular polarization allows viewers to tilt their heads without losing the 3D effect. This is the technology used in many modern cinemas, including the popular RealD 3D system.

Autostereoscopy

Autostereoscopy refers to 3D displays that do not require glasses. These devices use techniques like lenticular lenses or parallax barriers to direct different images to each eye. A well-known example of autostereoscopy is the Nintendo 3DS, a gaming device that uses parallax barrier technology to display 3D images without the need for glasses.

Autostereoscopic displays are limited in terms of the viewing angle, meaning that the 3D effect can only be experienced from specific positions relative to the screen.

Volumetric Displays

Volumetric displays use physical mechanisms to create light points in a three-dimensional space. These displays do not rely on stereoscopic effects but instead use voxels, which are 3D equivalents of pixels. The result is a display that can be viewed from any angle, giving a more immersive experience.

While volumetric displays are still in development and not widely available, they hold promise for future applications in fields such as medical imaging and virtual reality.

Holographic Displays

Holographic displays attempt to recreate a full light field, allowing the viewer to see different angles of an image depending on their position. This technology uses wavefront reconstruction to display images in a three-dimensional space without the need for special glasses. Holographic displays can present depth more naturally, reducing visual fatigue often associated with traditional stereoscopic displays.

Some recent innovations in this field include waveguide-based displays, which superimpose 3D images onto the real world without bulky equipment. This technology is gaining traction in augmented reality (AR) applications.

Conclusion

In this chapter, we explained various types of 3D viewing devices, from the basics of stereoscopic displays and progressing through several innovative technologies.

We discussed stereoscopes, View-Masters, head-mounted displays, active shutter systems, anaglyph 3D, and polarization systems. We also touched upon advanced technologies like autostereoscopic, volumetric, and holographic displays.