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Explore the accuracy of rendering techniques in depicting Pacioli's Rhombicuboctahedron through PechaKucha style presentation.
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BID Lunch, May 13, 2014PechaKucha Style Presentation: Physically Correct Rendering of Pacioli’s Rhombicuboctahedron Carlo H. Séquin and Raymond Shiau University of California, Berkeley
“Ritratto di Frà Luca Pacioli” (1495) Museo e Gallerie di Capodimonte in Naples, Italy
RCO = Rhombi-cuboctahedron • Archimedean solid: 8 triangles, 18 square faces RCO “Leonardo style”
Praise of the Pacioli RCO • … a masterpiece of reflection, refraction, and perspective.[George Hart] • Its surface reflects a view out an open window, showing the Palazzo Ducale in Urbino.[Margaret Davis]
How Accurate Is the Rendering ? • … do the reflections show that the window is high up towards the left? Or rather towards the bottom right? Both do not really make sense. • … the way the images are formed doesn’t seem very realistic at all.[Joost Rekveld]
Comparison to a Physical Model Model by Claude Boehringer -- quite different surroundings.
Do a Computer Graphics Rendering! Which of these pictures is correct? There are many parameters to adjust! Difficulties with the glass/water interface.
Matching the Viewing Geometry Front view Side view
Depicting Surface Reflections 0° 170° 146° A line reflected across a non-flat dihedral angle results in a “sheared” discontinuity. Pasted-on rectangular “sticker” is wrong!
Simple Refraction in Water Painting no refraction with refraction Painter did not observe any refraction!(probably did not have a water-filled model)
Multiple Refraction- & Mirror-Events M=1 R=2 M • Limiting the depth of the ray-trace tree: M=1 M=8R=2 R=8 >3R
Glass / Water Interface view Water half-cube behind glass half-cube water/gap/glasswater/glass (fused)
Water Half-cube behind Glass Half-cube Tracing ray-bundles Properly fused interface
Water Half-cube behind Glass Half-cube Ray-bundles Properly fused interface Ray-bundles
The Complete RCO The various materials and interfaces:Opaque filler (O), Water (W), Glass (G), G/W-interface (I)
Modeling the Whole RCO M=1 R=3
Modeling the Whole RCO R=4 M=1, R=4
Modeling the Whole RCO M=1, R=6 M=R=10 (max) = “ground truth” ?
RCO in Pacioli’s Room Slightly exaggerated tinting Set-up
Final Comparison 1495 Painting 2014 Computer Rendering