stereoscopic workflow - people · stereoscopic workflow ben kitching explains how to create a...

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In association with Sony About the author Ben Kitching is a 3D and CAD consultant for Jigsaw Systems. His current projects include researching cost-effective stereoscopic workflows along with his normal duties of installing and configuring render farms STAGE ONE Anatomy of a stereoscopic rig The first instinct, knowing what we already know, is to take two cameras and have them converge on the subject of our animation. To realise why this approach won’t work we need to consider how the image will look when projected onto a screen. The image below shows an exaggeration of this effect with the image projected onto the white screen being distorted compared to the actual object… 01 The revised concept We could solve this problem by keeping the cameras parallel to each other so that their projection planes line up. This corrects the distortion but it also cuts down the usable area of our image. We can only use the portion of the image that can be seen by both cameras. The diagram below shows the extent of the image loss which would make it difficult to compose the shot. 02 Applying film offset One way to correct this is to keep the cameras parallel but skew the frustums so that both camera projection planes occupy the same area. We can do this using a parameter called film offset (shown in figure top right). You will find film offset controls in the camera settings within Cinema 4D, Maya, and modo. Similar settings are available in 3ds Max (skew modifier), Softimage (optical center shift) and Blender (camera shift). Stereoscopic workflow Ben Kitching explains how to create a stereoscopic camera rig in your 3D modelling app of choice, so that you can create a stereoscopic 3D film W FOR Maya, Cinema 4D, 3ds Max, Blender, LightWave 3D or modo ALSO REQUIRED Modelling software, Photoshop, After Effects or similar compositing software 3DTV.at Stereoscopic Player Red/cyan anaglyph glasses TIME TAKEN Around an hour TOPICS COVERED Building a stereoscopic camera rig Previewing and outputting your final animation Making your scene comfortable for viewing ON THE WEB Video walkthrough using Maya as an example Maya project file Full-size screenshots 3dworldmag.com/ sonycompetition Step-by-step Any software Animation e see the world in three dimensions because the separation between our eyes (our binocular disparity) means each of them sees the world from a slightly different viewpoint. Our brains use the disparity between these two images to judge depth. Creating a 3D film, be it CG or live action, involves using two cameras to capture a scene from two separate viewpoints, which are then shown independently to each eye fooling the brain into perceiving depth. This tutorial shows you the ins and outs of creating a stereoscopic camera rig in Maya, but the aim is to concentrate on the theory of creating such a rig so you can apply this to your own projects. » Convergence of projection planes using film offset, note the skewed frustums STAGE TWO Building a stereoscopic rig Sebastian Schneider has scripted a rig for Blender along with a tutorial on its use on his blog. The script is based on the below theories and includes controls for the zero parallax and interaxial separation, as well as anaglyph previewing. Before we dive into the tutorial, we need to define a few key terms… Zero Parallax Plane This is effectively the screen depth: anything in front of the zero parallax plane will appear to float outside of the screen and anything behind it will appear inside the screen. Interocular Distance This is the distance between the viewer’s eyes. Commonly referred to as the IOD, the average for humans is 6.35 centimetres. Interaxial Distance This is the distance between two stereoscopic cameras and is generally set to match the IOD. The interaxial distance can be raised or lowered to exaggerate or decrease the depth effect. Parallax The apparent displacement or difference in the apparent position of an object viewed along two different lines of sight. 03 Setting up the stereoscopic camera rig quickly in six steps A Place a single camera into your scene and set the target distance of the camera to your intended zero parallax plane. You should also set the focal length if you intend to use any depth of field effects. This centre camera will be used to help compose your shot. Bernard Mendiburu’s book 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen is an excellent source of information on the theory and practice of making stereo 3D films. Louis Marcoux’s Blog – Focused on 3ds Max Louis Marcoux’s blog has some very useful information on stereoscopy along with a downloadable stereo camera rig for 3ds Max. area.autodesk.com/ blogs/louis/ Sebastian Schneider’s blog contains a wealth of information on stereo camera rigs along with his own stereo rig for Blender and a tutorial on its use. noeol.de/s3d/ You can download the 3DTV.at Stereoscopic Player from the 3dtv. at site. There you’ll find a free version available which is capable of playing back a maximum of five minutes of footage. 3dtv.at/Downloads/ Index_en.aspx Useful resources While we’ve tried to cover as much of the theory as possible this issue, there’s plenty of stereoscopic resources worth checking out… Anatomy of a stereoscopic rig Some modellers have stereoscopic render functionality built in. This means the hard work of creating a rig has already been done for you. If you are using one of the following apps you may want to skip the example and read the notes on comfortable scene layout. Maya Maya has contained a comprehensive stereo camera rig since the 2009 version. It is called StereoCamera and can be accessed from the Create camera menu. This rig gives you access to controls for the zero parallax plane and interaxial distance along with visual feedback regarding comfortable stereo areas. Maya can also give a live stereoscopic preview in the viewport with support for anaglyph along with more exotic display technologies such as polarised and shuttered glasses. LightWave 3D LightWave has support for stereo rendering on versions 9 and above, which is enabled in the Camera properties (left) and uses a rig setup similar to the example below. The only setting available is for the interaxial distance and there is no built-in preview as in Maya. 3ds Max 3ds Max has no official support for stereoscopic rendering although Autodesk blogger Louis Marcoux has scripted his own rig called StereoCamModifier. It includes controls to set interaxial separation and zero parallax as well as helper objects to define comfortable viewing areas and even generate an anaglyph preview. The rig is available for download on Louis’ blog on Autodesk’s Area website. modo 401 modo 401 also has support for stereo rendering. First you need to enable the Stereoscopic option in the render settings (left). This will then give you controls for the interaxial distance and zero parallax plane in your camera settings (bottom left). As with LightWave there is no built-in stereo preview. TRAINING Stereoscopic workflow Image distortion with converged cameras: the projected image is incorrect Parallel cameras improve distortion but waste a lot of the available image area Setting up a stereo camera rig isn’t hard – but requires tweaking to get it just right » WATCH THE VIDEO TUTORIAL Get a video showing the stereo 3D workflow from the competition website 3dworldmag.com/sonycompetition

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Page 1: Stereoscopic workflow - People · Stereoscopic workflow Ben Kitching explains how to create a stereoscopic ... final animation • Making your scene comfortable for viewing ON THE

In association with Sony

»

About the author Ben Kitching is a 3D and CAD consultant for Jigsaw Systems. His current

projects include researching cost-effective stereoscopic workflows along with his normal duties of installing and configuring render farms

STAGE ONEAnatomy of a stereoscopic rig The first instinct, knowing what we already know, is to take two cameras and have them converge on the subject of our animation. To realise why this approach won’t work we need to consider how the image will look when projected onto a screen. The image below shows an exaggeration of this effect with the image projected onto the white screen being distorted compared to the actual object…

01 The revised conceptWe could solve this problem by keeping

the cameras parallel to each other so that their projection planes line up. This corrects the distortion but it also cuts down the usable area of our image. We can only use the portion of the image that can be seen by both cameras. The diagram below shows the extent of the image loss which would make it difficult to compose the shot.

02 Applying film offsetOne way to correct this is to keep the

cameras parallel but skew the frustums so that both camera projection planes occupy the same area. We can do this using a parameter called film offset (shown in figure top right). You will find film offset controls in the camera settings within Cinema 4D, Maya, and modo. Similar settings are available in 3ds Max (skew modifier), Softimage (optical center shift) and Blender (camera shift).

Stereoscopic workflowBen Kitching explains how to create a stereoscopic camera rig in your 3D modelling app of choice, so that you can create a stereoscopic 3D film

W

FORMaya, Cinema 4D, 3ds Max, Blender, LightWave 3D or modo

ALSO REQUIRED• Modelling software,

Photoshop, After Effects or similar compositing software

• 3DTV.at Stereoscopic Player

• Red/cyan anaglyph glasses

TIME TAKENAround an hour

TOPICS COVERED• Building

a stereoscopic camera rig

• Previewing and outputting your final animation

• Making your scene comfortable for viewing

ON THE WEB• Video walkthrough

using Maya as an example

• Maya project file • Full-size

screenshots3dworldmag.com/sonycompetition

Step-by-stepAny softwareAnimation

e see the world in three dimensions because the separation between our eyes (our binocular disparity) means each of them sees the world from a slightly

different viewpoint. Our brains use the disparity between these two images to judge depth. Creating a 3D film, be it CG or live action, involves using two cameras to capture a scene from two separate viewpoints, which are then shown independently to each eye fooling the brain into perceiving depth. This tutorial shows you the ins and outs of creating a stereoscopic camera rig in Maya, but the aim is to concentrate on the theory of creating such a rig so you can apply this to your own projects.

»

Convergence of projection planes using film offset, note the skewed frustums

STAGE TWOBuilding a stereoscopic rigSebastian Schneider has scripted a rig for Blender along with a tutorial on its use on his blog. The script is based on the below theories and includes controls for the zero parallax and interaxial separation, as well as anaglyph previewing.

Before we dive into the tutorial, we need to define a few key terms…

Zero Parallax Plane This is effectively the screen depth: anything in front of the zero parallax plane will appear to float outside of the screen and anything behind it will appear inside the screen.

Interocular Distance This is the distance between the viewer’s eyes. Commonly referred to as the IOD, the average for humans is 6.35 centimetres.

Interaxial Distance This is the distance between two stereoscopic cameras and is generally set to match the IOD. The interaxial distance can be raised or lowered to exaggerate or decrease the depth effect.

Parallax The apparent displacement or difference in the apparent position of an object viewed along two different lines of sight.

03 Setting up the stereoscopic camera rig quickly in six steps

A Place a single camera into your scene and set the target distance of the camera to your intended zero parallax plane. You should also set the focal length if you intend to use any depth of field effects. This centre camera will be used to help compose your shot.

Bernard Mendiburu’s book 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen is an excellent source of information on the theory and practice of making stereo 3D films.

Louis Marcoux’s Blog – Focused on 3ds Max Louis Marcoux’s blog has some very useful information on stereoscopy along with a downloadable stereo camera rig for 3ds Max.area.autodesk.com/blogs/louis/

Sebastian Schneider’s blog contains a wealth of information on stereo camera rigs along with his own stereo rig for Blender and a tutorial on its use.noeol.de/s3d/

You can download the 3DTV.at Stereoscopic Player from the 3dtv.at site. There you’ll find a free version available which is capable of playing back a maximum of five minutes of footage.3dtv.at/Downloads/Index_en.aspx

Useful resourcesWhile we’ve tried to cover as much of the theory as possible this issue, there’s plenty of stereoscopic resources worth checking out…

Anatomy of a stereoscopic rig Some modellers have stereoscopic render functionality built in. This means the hard work of creating a rig has already been done for you. If you are using one of the following apps you may want to skip the example and read the notes on comfortable scene layout.

MayaMaya has contained a comprehensive stereo camera rig since the 2009 version. It is called StereoCamera and can be accessed from the Create camera menu. This rig gives you access to controls for the zero parallax plane and

interaxial distance along with visual feedback regarding comfortable stereo areas. Maya can also give a live stereoscopic preview in the viewport with support for anaglyph along with more exotic display technologies such as polarised and shuttered glasses.

LightWave 3DLightWave has support for stereo rendering on versions 9 and above, which is enabled in the Camera properties (left) and uses a rig setup similar to the example below. The only setting available is for the interaxial distance and there is no built-in preview as in Maya.

3ds Max3ds Max has no official support for stereoscopic rendering although Autodesk blogger Louis Marcoux has scripted his own rig called StereoCamModifier. It includes controls to set interaxial separation and zero parallax as well as helper objects to define comfortable viewing areas and even generate an anaglyph preview. The rig is available for download on Louis’ blog on Autodesk’s Area website.

modo 401modo 401 also has support for stereo rendering. First you need to enable the Stereoscopic option in the render settings (left). This will then give you controls for the interaxial distance and zero parallax plane in your camera settings (bottom left). As with LightWave there is no built-in stereo preview.

TRAINING Stereoscopic workflow

Image distortion with converged cameras: the projected image is incorrect

Parallel cameras improve distortion but waste a lot of the available image area

Setting up a stereo camera rig isn’t hard – but requires tweaking to get it just right

»

WATCH THE VIDEO TUTORIALGet a video showing the stereo 3D workflow from the

competition website 3dworldmag.com/sonycompetition

Page 2: Stereoscopic workflow - People · Stereoscopic workflow Ben Kitching explains how to create a stereoscopic ... final animation • Making your scene comfortable for viewing ON THE

In association with Sony

04 Previewing your sceneBefore committing to the final output

you should preview your work. Export full resolution images at strategic points – for example when objects are at their closest or farthest away from the zero parallax plane or at points along a camera’s animated path. You should render a separate image out from each camera and use 3dtv.at.com’s

07 Use the comfortable viewing areas as a guide

The comfortable viewing area should only be thought of as a guideline; you can get away with objects being outside this area especially if

they move quickly through it and then out of shot. Problems occur if you have static objects outside of this given range. A good way to check this effect is to look at the separation between the left and right images of your anaglyphs – generally if the separation on objects at the very front or back of your scene is more than around 6cm it will be uncomfortable to view. This constraint varies with screen size and if you set a particular object to the limits of its separation on a small screen, blowing it up to a larger screen will increase this separation and could break your 3D effect. Ideally you should be conservative with the separation to ensure comfort on a range of screen sizes.

08 Handling depthIf you have a scene that is very deep

you may need to render the background off on a separate layer with different stereo parameters or even use your centre camera for no stereo effect at all to ensure comfortable viewing. The area outside the screen (in front of the zero parallax plane) should also be used with care. Ideally no object should stay in this area for too long.

One way to increase the comfortable viewing distance is to use depth of field to blur the areas outside of the comfort zone.

09 The stereoscopic windowThe display screen is the window into

your stereoscopic world. You should not let anything that is outside this window touch its edges. Your eyes will tell you that it is outside the screen due to its parallax, but your common sense will tell you it is inside the screen because it is occluded by the edge of the screen. This conflict of information will ruin the illusion of depth. You should trim any continuous surfaces such as ceilings or floors to the zero parallax plane for the same reason. You can see the right and wrong effects with your anaglyph glasses in figure 6. The satellite appears outside the screen on the left image yet as soon as it touches the side of the screen as in the right image the effect is lost.

10 Outputting the final animationThe final render can be thought of as

two separate animations, one for each eye. If your software contains tools for batch rendering you can save out two copies of your scene, one with the left camera active and the other with the right camera active and batch render these two files together. For

the Sony competition you should render out either a TIFF or TARGA image sequence for each eye at a resolution of 1,920 x 1,080.

To prepare your initial entry you’ll need to use After Effects or similar compositing software to first horizontally compress each image sequence to a resolution of 960 x 1080 then arrange the two sequences side by side, with the left image on the left, to get a final size of 1,920 x 1,080 (see image 10 above). Note how each image is squashed horizontally – this is done so that stereoscopic video can fit into the same bandwidth as standard HD video. On playback the images will be expanded to fill the entire 1,920 x 1,080 frame.

11 The final outputThe left and right eye sequences have

been horizontally compressed into a 1,920 x 1,080 frame to fit the same bandwidth as HD video for

B Now we need to set up the left and right cameras that will give us our stereoscopic effect. To start you should separate your left and right cameras by 6.3cm. To do this copy your original camera twice, moving one copy 3.15cm to the left and the other 3.15cm to the right.

C You should then create an expression so that moving one of these new cameras will move the other in the opposite direction. This will help later on when we need to play with the interaxial distance to optimise the 3D effect.

D Next you should name your cameras left, right and centre according to their position and group all of them within a null object so that you can move or animate them as one.

E Next use the Film Offset on the left and right cameras so that their projection planes overlap (as shown in the figure on page 59).

F Finally, you should create an expression between the left and right Film Offset values so that moving one will move the other in the opposite direction. This will save you from having to adjust the two values independently whenever you change the interaxial distance.

We now have an optimally configured camera rig. However there are a few things to consider before outputting our scene: you will have to experiment with separation between the cameras and the placement of objects in your scene to achieve a stereo effect that works with your particular scene.

initial judging. Your entry should have stereo audio and use any codec that can be played back on a standard PlayStation 3. A list of compatible codecs can be found here: manuals.playstation.net/document/en/ps3/current/video/filetypes.html.

However, make sure you also keep the original image sequences: if your movie is chosen for inclusion on the 3D demo Blu-ray Disc, you will need to provide them so Sony’s engineers can generate the S-3D master. Audio should be provided as a 48KHz WAV file in either stereo or surround format.

For more information, helpful video tutorials and a forum, visit 3dworldmag.com/sonycompetition

With thanks to…Finally thanks to Google’s 3D Warehouse, planetpixelemporium.com and Roy Uyematsu (roystarman.com) for the textures, images and models used in my S.I.D. satellite example.

stereoscopic player (Windows only) to view your images. Grey anaglyph is the best way to preview your stereo effect without a special screen.

05 If you’re on a Mac, just use Photoshop instead

If you are working on a Mac, you can still preview your image by creating an anaglyph from your left

and right images using this method in Photoshop…Open both the left and right images together. Using the channels palette select the red channel of the left image. Select > All and copy this entire channel. Now simply select the red channel of the right image and then paste the copied channel from the left image into it. Finally switch back to the RGB view and you should see your anaglyph image.

06 Comfortable scene layout Our eyes can only focus within a limited

depth range: their ‘depth of field’. In the real world anything in front of or behind this depth of field appears out of focus. In a CG scene it is entirely possible to have objects in focus exceeding this range. This will cause our eyes to try and focus on too large a depth range causing discomfort and loss of the stereo effect. A good rule of thumb is that no object should be further from the zero parallax plane in either direction than half way between the camera and the zero parallax plane.

TRAINING Stereoscopic workflow

04

05

06

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09

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Until 3D monitors are commonplace, anaglyph images are still the best way to test your scene

Warning! Window violation in progress

Stereoscopic Player supports a vast amount of different viewing methods

Anaglyph separation distance can highlight areas of discomfort

The final stereo images compressed into the competition entry format