1 / 17

The Lit Sphere:

The Lit Sphere:. A Model for Capturing NPR Shading from Art Peter-Pike J. Sloan William Martin Amy Gooch Bruce Gooch. Motivation. Interactive shading of 3D characters Artists shading study on the sphere. Motivation. Acquire reflectance from real world

rane
Download Presentation

The Lit Sphere:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Lit Sphere: A Model for Capturing NPR Shading from Art Peter-Pike J. Sloan William Martin Amy Gooch Bruce Gooch

  2. Motivation • Interactive shading of 3D characters • Artists shading study on the sphere

  3. Motivation • Acquire reflectance from real world • Use to illuminate and place synthetic objects in scene

  4. Previous Work • NPR • Lake2000 – Cartoon Shading • Gooch98 – Technical Illustration • Praun2001 – Real time hatching • Acquiring Shading Models • Environment Maps • Blinn76,Miller84,Green86 • More general models • Yu98, Yu99, Sato99

  5. Simple Idea • “Paint by normals” • Surface parameterized by normal field • Store shading model in a environment mapped indexed by surface normal (not reflection vector)

  6. Simple Examples

  7. Simple Demo

  8. Creating the Environment Map • Could just paint it • requires artistic ability

  9. Extracting EMap

  10. Creating the Environment Map • “Extract” from source artwork • Map triangles from source onto sphere • Simple control over parameterization

  11. Fill in gaps Render at multiple scales Blend into final image (1-dest,1) Could solve for colors by minimizing some high pass filter (ala Hakura99 and McCool01) Texture synthesis Creating The Environment Map

  12. Simple Demo 2

  13. More Examples

  14. Issues • Texture “crawls” when view changes • Texture as a function of curvature – seems odd but works better then one would expect, flat regions have no variation • Could attach texture to the surface, or at least separate it from shading • Probably want texture anchored on the surface, but able to respond to shading changes – kind of like Praun2001 but not just for hatching

  15. Simple Hacks • Have separate “texture sphere” that rotates with the object • Really should just live on the surface, bad parameterization for something very coherent • Just use cube maps • Modulate final results with “canvas” image • Kind of like detail textures, sometimes can make the “swimming” less objectionable

  16. Conclusions • Simple way to interactively shade objects based on source artwork • Works ok if you aren’t trying to transfer something that has strong texture • Probably should factor the model into more then 1 term…

  17. Acknowledgments • University of Utah Computer Graphics groups • Louise Bell, Grue, Susan Ashurst • Michael Cohen, Adam Finkelstein, James Mahoney, Wolfgang Heidrich • DARPA, NSF STC for CG&SV

More Related