Taking stereoscopic tours of 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 Viewing Nearer-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 a small 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. should correlate 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. should correlate with stereo distance Each eye should see just its own image - “ghosting” shouldn't be distracting. It's worst on 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 screen with 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 environment Shrinking in virtual scale as we approach...

Dynamics – Changing scale along path Touring in a multi-scale environment Shrinking in virtual scale as we approach... This crabwise sidling path gives better motion parallax to complement the stereo depth cues

Dynamics – Changing scale along path Touring in a multi-scale environment Shrinking in virtual scale as we approach... This crabwise sidling path gives better motion parallax 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 on galactic core, but there are many bright stars much nearer, hurtling by us? If eye separation is enough to give good sense of depth, the foreground stars are likely too close to fuse at all – extreme disparity. Renderer hack, tied to motion blur: streak dimming!