Shadows vs. StereoShadows vs. StereoDaniel WalshDaniel Walsh

Aims of the ProjectAims of the Project

• 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

MotivationMotivation

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

Choosing a Shadow Choosing a Shadow AlgorithmAlgorithm

• Three Main AlgorithmsThree Main Algorithms

Shadow VolumesShadow Volumes

Shadow MapsShadow Maps

Ray TracingRay Tracing

Shadow MappingShadow Mapping

• Scene is drawn twice Scene is drawn twice

Once from the lightOnce from the light’’s s point of viewpoint of view

Once from the Once from the cameracamera’’s point of views point of view

Shadow MappingShadow Mapping

Pixels visible to light Pixels visible to light are drawn lit in are drawn lit in camera viewcamera view

Pixels occluded or Pixels occluded or outside of the lightoutside of the light’’s s field of view are field of view are drawn shadoweddrawn shadowed

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

Stereo RenderingStereo Rendering

• Polarised Passive StereoPolarised Passive Stereo

A polarised screen coupled with 3D glasses are A 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 fools The difference between the two images fools the brain into thinking itthe brain into thinking it’’s seeing three s seeing three dimensions rather than a flat planedimensions rather than a flat plane

Stereo RenderingStereo Rendering

The scene is drawn once The scene is drawn once for each eyefor each eye

A shader interlaces the A shader interlaces the two images so that they two images so that they can be output by the can be output by the display to each eye display to each eye individuallyindividually

ExperimentExperiment

• Part 1Part 1

Users are asked to identify which, of two objects Users are asked to identify which, of two objects is nearer the camera in a sceneis nearer the camera in a scene

• Part 2Part 2

Users are asked to compare the aesthetic value Users are asked to compare the aesthetic value of a pair of scenes rendered using different of a pair of scenes rendered using different techniquestechniques

Experimental ResultsExperimental Results• Part 1Part 1

Users were more successful with both shadows Users were more successful with both shadows and stereo, with stereo showing a slightly larger and stereo, with stereo showing a slightly larger improvement.improvement.

Experimental ResultsExperimental Results• Part 2Part 2

Overall shadows were preferred aesthetically, Overall shadows were preferred aesthetically, with stereo performing far better with shadows with stereo performing far better with shadows included.included.

Thanks For ListeningThanks For Listening

• Any Questions?Any Questions?