This document discusses an experiment to determine whether shadow rendering or stereoscopic 3D provides better depth cues and is more aesthetically pleasing. The experiment asks users to identify which of two objects is nearer the camera and to compare scenes rendered with different techniques. For depth cue identification, users performed better with both shadows and stereo, with stereo showing a slightly larger improvement. Aesthetically, shadows were preferred overall but stereo performed far better when combined with shadows. The document provides background on shadow mapping and stereo rendering techniques.

1. Shadows vs. StereoShadows vs. Stereo
Daniel WalshDaniel Walsh

2. Aims of the ProjectAims of the Project
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To Determine Through Experimentation Which,To Determine Through Experimentation Which,
of Shadow Rendering and Stereoscopic 3Dof Shadow Rendering and Stereoscopic 3D
Provides better depth cuesProvides better depth cues
Is more aesthetically pleasing to the userIs more aesthetically pleasing to the user

3. MotivationMotivation
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As 3D displays become more and moreAs 3D displays become more and more
common in the consumer space it becomescommon in the consumer space it becomes
necessary to attempt to gauge the actualnecessary to attempt to gauge the actual
improvement over standard 2D technologies.improvement over standard 2D technologies.

4. Choosing a ShadowChoosing a Shadow
AlgorithmAlgorithm
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Three Main AlgorithmsThree Main Algorithms
Shadow VolumesShadow Volumes
Shadow MapsShadow Maps
Ray TracingRay Tracing

5. Shadow MappingShadow Mapping
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Scene is drawn twiceScene is drawn twice
Once from the lightOnce from the light’’ss
point of viewpoint of view
Once from theOnce from the
cameracamera’’s point of views point of view

6. Shadow MappingShadow Mapping
Pixels visible to lightPixels visible to light
are drawn lit inare drawn lit in
camera viewcamera view
Pixels occluded orPixels occluded or
outside of the lightoutside of the light’’ss
field of view arefield of view are
drawn shadoweddrawn shadowed

7. Shadow MappingShadow Mapping
No prior knowledge of scene neededNo prior knowledge of scene needed
No overhead for more complex objectsNo overhead for more complex objects
LightLight’’s view must be stored in a texture units view must be stored in a texture unit
Less accurate than shadow volumesLess accurate than shadow volumes

8. Stereo RenderingStereo Rendering
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Polarised Passive StereoPolarised Passive Stereo
A polarised screen coupled with 3D glasses areA polarised screen coupled with 3D glasses are
used to transmit a different image to each eyeused to transmit a different image to each eye
The difference between the two images foolsThe difference between the two images fools
the brain into thinking itthe brain into thinking it’’s seeing threes seeing three
dimensions rather than a flat planedimensions rather than a flat plane

9. Stereo RenderingStereo Rendering
The scene is drawn onceThe scene is drawn once
for each eyefor each eye
A shader interlaces theA shader interlaces the
two images so that theytwo images so that they
can be output by thecan be output by the
display to each eyedisplay to each eye
individuallyindividually

10. ExperimentExperiment
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Part 1Part 1
Users are asked to identify which, of two objectsUsers are asked to identify which, of two objects
is nearer the camera in a sceneis nearer the camera in a scene
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Part 2Part 2
Users are asked to compare the aesthetic valueUsers are asked to compare the aesthetic value
of a pair of scenes rendered using differentof a pair of scenes rendered using different
techniquestechniques

11. Experimental ResultsExperimental Results
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Part 1Part 1
Users were more successful with both shadowsUsers were more successful with both shadows
and stereo, with stereo showing a slightly largerand stereo, with stereo showing a slightly larger
improvement.improvement.

12. Experimental ResultsExperimental Results
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Part 2Part 2
Overall shadows were preferred aesthetically,Overall shadows were preferred aesthetically,
with stereo performing far better with shadowswith stereo performing far better with shadows
included.included.

13. Thanks For ListeningThanks For Listening
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Any Questions?Any Questions?