Taking stereoscopic toursof astronomical scenes

Stuart Levy with Robert Patterson

Advanced Visualization Lab - AVL at NCSA Nat'l Center for Supercomputing Applications,

University of Illinois Urbana-Champaign

October 17, 2011

Stereoscopic Rendering

Two views from slightly different viewpoints

Separation vector normally parallel to screen

Ideally, how virtual camera sees virtual screen should match (up to arbitrary scaling) how real viewer sees real screen.

Stereoscopic Viewing

Viewer sees L/R disparity, interprets as distance...

… nearer than / coincident with / farther than screen plane …

Stereoscopic ViewingNearer-than-screen (in-theater) can look exciting. Take care:

Comfortable convergence angle: more than 1-2˚ can cause flyswatting (fun!) and eyestrain.

Large virtual eye separation minimizes things.  

Should a galaxy look majestically grand? Or be a toy within a large galaxy cluster?

Rendering, 2: Get Infinity Right(or know why you aren't!)

Infinitely distant objects have zero disparity...

So real images should be separated by viewer's real eye separation. Display-size dependent!

Hundreds of pixels of image shift on asmall panel, dozens on a large screen.

Stereo Visual Cues

Stereo vision is pretty forgiving if you avoid extreme convergence and conflicting cues...

Occlusion: If stereo puts thing X nearer than (real) screen, then X shouldn't be sliced by (virtual) screen edge.

Stereo Visual Cues

Stereo vision is pretty forgiving if you avoid extreme convergence and conflicting cues...

Occlusion: If stereo puts thing X nearer than (real) screen, then X shouldn't be sliced by (virtual) screen edge.

Motion-parallax, etc. shouldcorrelate with stereo distance

Stereo Visual Cues

Stereo vision is pretty forgiving if you avoid extreme convergence and conflicting cues...

Occlusion: If stereo puts thing X nearer than (real) screen, then X shouldn't be sliced by (virtual) screen edge.

Motion-parallax, etc. shouldcorrelate with stereo distance

Each eye should see just its own image - “ghosting” shouldn't be distracting. It's worston small displays (widely separated images)and high-contrast material.

Display Challenge: small = large?

If we set up the viewing geometry right,we should be able to use a small display

to test imagery meant for a large screen.

“Right” means...

correctly handle infinity (image shift), and

view from a point that sees the small screenwith the proper angular field-of-view(~90˚ wide for IMAX film from a typical seat)

that occlusion isn't too troublesome

Dynamics – Changing scale along path

Touring in a multi-scale environmentShrinking in virtual scale as we approach...

Dynamics – Changing scale along path

Touring in a multi-scale environmentShrinking in virtual scale as we approach...

This crabwise sidling path gives better motionparallax to complement the stereo depth cues

Dynamics – Changing scale along path

Touring in a multi-scale environmentShrinking in virtual scale as we approach...

This crabwise sidling path gives better motionparallax to complement the stereo depth cues

Autoscaling during choreography

Feature added to Virtual Director:

“autoscale zones” where scale is determined by distance from that zone's center point,

over some range of distances

Autoscaling during choreography

Feature added to Virtual Director:

“autoscale zones” where scale is determined by distance from that zone's center point,

over some range of distances

e.g. one zone at Earth, one at Tycho SN remnant, one at Milky Way center

Autoscaling during choreography

Feature added to Virtual Director:

“autoscale zones” where scale is determined by distance from that zone's center point,

over some range of distances

e.g. one zone at Earth, one at Tycho SN remnant, one at Milky Way center

Scale sets flight speed as well as stereo:auto-shrinking helps fly smoothly along approach curves.

Trick: dimming foreground clutter

Does story line say we should focus attention ongalactic core, but there are many bright stars much

nearer, hurtling by us?

If eye separation is enough to give good senseof depth, the foreground stars are likely too close to fuse at all – extreme disparity.

Renderer hack, tied to motion blur: streak dimming!