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# Stereoscopic Camera

## Introduction

• This lesson will take you through creating a Stereoscopic render
• The information centers around the V-Ray Stereoscopic Camera
• This lesson topic is approximately 15 minutes in length
• Lesson covers all 3 Learning Cycles for the Lesson Topic – Lecture, Demonstration, and Activity

## Overview

Goal - Configure the left and right eye renders for stereo viewing

Objective – Setting up and configuring Stereoscopic camera for proper stereo output

Outcome – You will be able to set the scene up for a stereoscopic render

## Lecture

### 1. Terminology

Here’s some terms to be aware of when thinking about the Stereoscopic camera

• Stereoscopy
• Creating the illusion of three-dimensional depth in two-dimensional images.
• Eye distance / Interocular distance (interaxial separation)
• The amount of stereo effect is defined, in part, by the separation of the camera lenses, which defines the relative parallax differential between the left and right eye images
• Convergence / Focal plane
• The point in 3D space where the left & right eye images meet in the rendered image, causing objects to appear in front or past the screen to the viewer
• Divergence
• The need for the eyes to go wall-eyed, (i.e. rotate outward) to fuse the two separate left & right eye images into one
• Stereo Window
• Best imagined as photo frame where objects get be in 3D viewing space behind, in the middle or outside of the frame

### 2. Stereoscopic Camera

a) Stereoscopy

• Is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision
• Most stereoscopic methods present two offset images separately, one each to the left and right eye of the viewer
• These 2D images are then combined in the brain to give the perception of 3D depth. Like magic. Science magic!
• Binocular Vision - Your eyes are approximately two-and-a-half inches or 6cm apart (‘Interocular distance’), so they see the same image from slightly different angles
• Your brain combines these two images and you are able to gauge distance and depth

b) Retinal Disparity
• When we look at objects at different distances from us, the images of those objects will be projected on our retinas in slightly different locations for each eye
• Our brain can interprets this “Retinal Disparity” and helps us to determine depth
• In 3D with a stereo camera the same thing happens: Each camera in the stereo camera sees the scene in slightly different horizontal positions
• The Disparity is greater with a larger Eye Distance
• We call this difference Parallax

c) Convergence

• The convergence point of a 3d image determines where the object appears in relation to the screen
• Our eyes focus & converge at a single point on the screen plane (where the image is projected or displayed)
• When viewing 3D, our eyes focus on the screen, but we can perceive the image to converge on a point anywhere along the Z-axis
• The convergence point in 3d imagery is the point at which the left and right eye images align
• Convergence in an image may be adjusted by angling the two lenses inward to each other, or by moving the left/right eye images horizontally in post-production
• In a 3d image, objects in front of this convergence point appear to be in front of the screen, and those beyond the convergence point appear to be beyond the screen

d) Real World Stereo Cameras
• In the real world a Stereo camera is a camera with either two lenses or is a dual camera setup
• This allows the two images to be combined to create an illusion of depth
• The distance between the lenses in a typical stereo camera (the intra-axial distance) is about the distance between a typical person’s eyes

e) 3D World Stereo Cameras
• In the 3d world a Stereo camera is a rig where two cameras are controlled with one set of parameters
• This allows two images to be rendered at once
• The distance between the two virtual lenses can be changed
• V-Ray provides different ways that the two images rendered out can be viewed at once

f) 3D Viewing Systems

• Active Viewing Systems
• An Active 3D Shutter system –Works by presenting the image intended for one eye on the screen while blocking the other eye's view with glasses. When alternating between the two eyes rapidly like this, your mind fuses the two images into a single 3D image.
• Passive Viewing Systems
• Polarization systems - 2 projected images are superimposed onto the same screen through polarizing filters on the projector. The viewer wears low-cost eyeglasses which also contain a pair of opposite polarizing filters, one for each eye.  Each filter only passes light which is similarly polarized and blocks the opposite polarized light, so one eye sees one image and not the other.
• Interference filter systems - Uses specific wavelengths of red, green, and blue for the right eye, and different wavelengths of red, green, and blue for the left eye. Eyeglasses filter out the very specific wavelengths, allowing the wearer to see a full color 3D image
• Color anaglyph systems - The 3D effect achieved by means of encoding each eye's image using filters of different (usually chromatically opposite) colors, typically red and cyan

g) The Stereo Window
• The surface of your screen is the point of Zero Parallax
• Best thought of as an empty photo frame

h) Parallax (Retinal Disparity) – The difference in position of the two camera / eyes
• Positive Parallax
• Objects appear behind the Stereo Window / Screen
• Negative Parallax
• Objects appear in front of the Stereo Window / Screen, appearing to “come out at you from the screen”

The Red Plane shows the point of Zero Parallax in two differing positions

i) Eye distance / (interaxial separation)

• Interaxial Separation is the distance between the two cameras
• Defines in part the amount of stereo effect
• Should be close to a person’s inter-ocular distance
• Changing the eye distance
• The wider the interaxial, the more exaggerated the depth
• The smaller the interaxial distance, the less depth we perceive

Eye Distance: 2.0

Eye Distance: 3.0

Eye Distance: 9.0

j) Key Parameters for the V-ray Stereoscopic camera
• Eye Distance – Specifies the eye distance for which the stereoscopic image will be rendered
• Specify Focus – Allows you to manually specify the focus distance for the camera
• Focus Distance – Manually specify the focus distance of the camera in scene units
• Focus Method – Specifies the focus method for the two views
• Interocular Method – Specifies how the 2 virtual cameras will be placed in relation to the real camera in the scene
• View – Specifies which of the stereoscopic views will be rendered
• Adjust Resolution – When turned on, this option will automatically adjust the resolution for the final image rendered
• Panoramic Pole Merging - This section is used when rendering a panoramic view with stereoscopy (for example a Spherical camera with FOV=360 degrees). It allow us to avoid artefacts when looking upward and downward.

k) Adding a Stereoscopic Camera to the scene
• Stereo Camera Attributes can be added to any camera by selecting the shape node of the camera & select the Stereoscopic camera attributes from the Attributes>VRay menu
• Another option is to use the Maya Stereo Rig - a rig of 3 cameras. The stereo effect can be controlled from the attribute editor of the centre camera.
• If you already have 2 separate cameras for the left/right eye in the scene then you can create a V-Ray Stereo Rig - from "Create/VRay/Create StereoRig from cameras"

## Conclusion

a) Eye Distance
• Controls the Interaxial separation of the two images
b) Focus Distance
• The distance from the camera to the point of convergence / the Focal Plane
c) Parallax
• Objects with Positive Parallax will appear behind the stereo window, those with Negative Parallax will appear in front of it

## Demonstration

Time to see it work!

Watch while I demonstrate how to add and setup a VRay Stereoscopic camera.

## Activity

Time to do it yourself!

Use the provided scene file to set up a VRay Stereoscopic camera