Cutting-Edge Photorealistic Image Synthesis in Architectural CAD Systems

1. Photorealistic Image Synthesisin CAD Systems(IKTA3 00101/2000) László Szirmay-Kalos Budapesti University of Technology and Economics Department of Control Engineering and Information Technology and Graphisoft R&D

2. The Project • A research project between BUTE and Graphisoft • Research topic: global illumination in architecturalCAD systems • January 2001 – April 2002 • Homepage: www.iit.bme.hu/~szirmay/ikta/index.html • Participants: • Project leader: dr. László Szirmay-Kalos (BUTE) • Advisors: dr. László Szirmay-Kalos (BUTE) and László Sparing (Graphisoft) • PhD students: György Antal, Ferenc Csonka (Graphisoft), László Kovács (BUTE), Benedek Balazs (BUTE), Szécsi László (BUTE) • Others: dr. Horváth Tamás (BUTE), Csaba Kelemen • The main results: scientific research and a new framework called RenderX for testing and implementing global illumination algorithms Photorealistic Image Synthesis in CAD systems

3. Graphisoft and ArchiCAD • Graphisoft was promoted in 1982 • It is the third software company in the AEC sector (Architecture, Engineering and Construction) • The leading product of Graphisoft is the ArchiCAD, which is an object oriented, 3D design software for the architecture and building industry Photorealistic Image Synthesis in CAD systems

4. Outlines • Objective of the project • Photorealistics image synthesis fundamentals • The result of the project • Products and applications Photorealistic Image Synthesis in CAD systems

5. Goal of the project • Global illumination image synthesis • Must be physically accurate • Solving the rendering equation • Identify all potential light paths • Conventional methods took hours to render • Interactive naviagation and animation • must produce new images in seconds Photorealistic Image Synthesis in CAD systems

6. The aim of image synthesis • In the virtual world, a virtual camera makes the photo of the scene. The camera sees the scene like this The camera looks into the world through a window Photorealistic Image Synthesis in CAD systems

7. The rendering equation • L= Le+ TL Photorealistic Image Synthesis in CAD systems

8. How does the Nature work? • 100 W light bulb emits 1042photon per second • The calculation of the intersected patches, that the photons hit is determined parallel with the speed of light • The photons are absorbed randomly or reflected into a random direction • Very little fraction of the emitted photons arrive finally to the eye Photorealistic Image Synthesis in CAD systems

9. Local Illumination Top: sharp (left) and soft (right) shadows on local illumination images Down: the global illumination image (H. W. Jensen, 1996) Photorealistic Image Synthesis in CAD systems

10. Global Illumination • Identify all the possible light paths via multiple reflections, from the light source to the eye Photorealistic Image Synthesis in CAD systems

11. Global Illumination • Follow the light paths from the camera to the eye with another method (Szirmay-Kalos László, 2000) Photorealistic Image Synthesis in CAD systems

12. Results • Publications in 2001: • László Szirmay-Kalos, Ferenc Csonka, György Antal: Global Illumination as a Combination of Continuous Random Walk and FiniteElement Based Iteration, Eurographics Conference, 2001 • Csaba Kelemen, László Szirmay-Kalos: A Microfacet Based Coupled Specular-Matte BRDF Model with ImportanceSampling,Eurographics Conference, 2001 • Csaba Kelemen, László Szirmay-Kalos: Simple and Robust Mutation Strategy for Metropolis Light Transport Algorithm, Dagstuhl Seminar on Monte-Carlo Methods in Rendering, 2001 • György Antal, László Szirmay-Kalos, Ferenc Csonka, Csaba Kelemen: Multiple Strategy Stochastic Iteration for Architectural Walkthroughs, Dagstuhl Seminar on Monte-Carlo Methods in Rendering, 2001 • Ferenc Csonka, László Szirmay-Kalos György Antal: Cost-Driven Multiple Importance Sampling for Monte-Carlo Rendering,MCM Conference, Salzburg, 2001 • György Antal, László Szirmay-Kalos, Ferenc Csonka, Csaba Kelemen: Multiple Strategy Stochastic Iteration for Architectural Walkthroughs, Technical Report, TR-186-2-01-17, Vienna, 2001 • Csaba Kelemen, László Szirmay-Kalos: Simple and Robust Mutation Strategy for Metropolis Light Transport Algorithm, Technical Report, TR-186-2-01-18, Vienna, 2001 • Ferenc Csonka, László Szirmay-Kalos György Antal: Cost-Driven Multiple Importance Sampling for Monte-Carlo Rendering,MCM Conference, Technical Report, TR-186-2-01-19, Vienna, 2001 • László Szirmay-Kalos, László Kovács, Ali Mohamed Abbas: Testing Global Illumination Methods with Analytically Computable Scenes Winter School of Computer Graphics Conf., 2001 • Roel Martínez, László Szirmay-Kalos, Mateu Sbert, Ali Mohamed Abbas: Parallel Implementation of Stochastic Iteration Algorithms, Winter School of Computer Graphics Conf., 2001 • László Szirmay-Kalos, György Antal, Mateu Sbert: Progressive Light Path Development, Winter School of Computer Graphics Conf., 2001 Photorealistic Image Synthesis in CAD systems

13. Results • Publications in 2002: • György Antal, László Szirmay-Kalos, Ferenc Csonka: Weighted Multipass Method Based on Stochastic Iteration and Random Walk Methods,Winter School Of Computer Graphics Conference, 2002 • Csaba Kelemen, László Szirmay-Kalos, György Antal, Ferenc Csonka: Simple and Robust Mutation Strategy for Metropolis Light Transport Algorithm, Eurographics Conference, 2002 • György Antal, László Szirmay-Kalos, Ferenc Csonka: Hemicube Shooting for Non-Diffuse Global Illumination, Spring Conference on Computer Graphics, 2002 • László Szirmay-Kalos, Vlastimil Havran, Balázs Benedek, László Szécsi: On the Efficiency of Ray-shooting Acceleration Schemes, Spring Conference on Computer Graphics, 2002 • Submitted papers: • György Antal, László Szirmay-Kalos, Ferenc Csonka, Csaba Kelemen: Multiple Strategy Stochastic Iteration for Architectural Walkthroughs • Ferenc Csonka, László Szirmay-Kalos, György Antal: Cost-Driven Multiple Importance Sampling for Monte-Carlo Rendering • Ferenc Csonka, László Szirmay-Kalos,Csaba Kelemen, György Antal: Dependent Tests driven Filtering in Monte-Carlo Global Illumination • György Antal, Ferenc Csonka: An Efficient And Robust Framework for Global Illumination Algorithms, 1st Hungarian Conference on Computer Graphics, 2002 • Ferenc Csonka, György Antal: A Multi-Phase Energy Preserving Filtering Method for Architectural Scenes,1st Hungarian Conference on Computer Graphics, 2002 Photorealistic Image Synthesis in CAD systems

14. Applications • The CAD programs connect to the global illumination application via 3D File formats: SCE, 3DS, VRML, MGF. Ray Bundle ArchiCAD SceWriter SCE 3D Studio RenderX 3DS, VRML, MGF,... Maya Photorealistic Image Synthesis in CAD systems

15. RenderX SCE 3DS VRML MGF Wireframe Local Illumination Ray-Tracing Ray Bundles (Gouraud) Ray Bundles (Phong) Path Tracing BidirectionalPath Tracing Metropolis ... Scaling Ward etc. Photorealistic Image Synthesis in CAD systems

16. 12 20 Stochastic IterationFinite element methods seconds 5 15 K patches Photorealistic Image Synthesis in CAD systems

17. Stochastic Iterationwith Phong shading Photorealistic Image Synthesis in CAD systems

18. Production qualityMonte-Carlo methods Photorealistic Image Synthesis in CAD systems

19. Walkthrough Animation • Place camera keyframes in ArchiCAD, • save scene, • calculate global illumination animation in RenderX Photorealistic Image Synthesis in CAD systems