Appearance Models for Graphics COMS , Lecture 1 Ravi Ramamoorthi

This course mainly focuses on materials But appearance depends on geometry, materials, lights Computer Graphics Rendering Geometry Lighting Materials Rendering Viewpoint Camera Image

Photorealistic Rendering Materials/Lighting (Texture Reflectance[BRDF] Lighting) Realistic input models required Arnold Renderer: Marcos Fajardo Rendering Algorithm 80’ s,90’ s : Physically based Geometry 70’ s, 80’ s : Splines 90’ s : Range Data

One Motivation: Digital Actors Final Fantasy Shrek

Computer Vision Analysis Most algorithms assume very simple lighting, materials Image Lighting Materials Vision alg. Viewpoint Camera Geometry

Inverse Rendering GeometryInverse Rend Viewpoint Camera Lighting Useful for acquiring material models in graphics Recognizing materials in vision Materials

Material Recognition Photographs of 4 spheres in 3 different lighting conditions courtesy Dror and Adelson

Complex materials Geometry, illumination, reflectance all important Often scales of geometry: Continuum of geometry/reflectance

Appearance important other areas Physics Materials science Cosmetics Building materials Car paints Textiles Art Using computer, complex simulations doable

Topics Modeling how light interacts with matter Measurement/acquisition of materials Image-based modeling and rendering Analytic methods Real-time rendering Focus mainly on computational methods

Outline Why appearance models? Examples of recent graphics images Approaches: Physical, structural, phenomenological methods Overview of course logistics

Outdoor Scenes Deussen et al. 98

Weathering: Metallic Patinas Dorsey and Hanrahan 96

Weathering: Flows Dorsey and Hanrahan 96

3D Texture (CURET database) Dana et al 97

Diffraction Stam 99

Subsurface Scattering Jensen et al. 2001

Hair Marschner et al.

Approaches Physical: Understand basic physics Structural: Understand microstructure (patinas, fabrics, layered models) Phenomenological: Empirical

Physical example: Fresnel Dielectrics: Increasing specularities grazing angles Metals: reflection changes with wavelength Copper-coloredCook-Torrance

Fresnel functions

(Micro)Structure Hair Fiber CD Plastic microfabric

Phenomenological Models Lambertian: Phong: –Really corresponds to extended light source Also, gaussian surfaces, splines, wavelets, Zernike polynomials, spherical harmonics, … BRDF itself phenomenological model

Taxonomy of Materials Renderman World PlasticMetalMatte ShinyPlastic ThinPlasticRoughMetal

Real World? Real World AnimalVegetableMineral Skin HairLeavesBarkMarble

Course Goals, Format Goal: Background and current research on appearance models in graphics and vision

Course Goals, Format Goal: Background and current research on appearance models in graphics and vision Columbia is the best place for this!!

Course Goals, Format Goal: Background and current research on appearance models in graphics and vision Columbia is the best place for this!! Format: Alternate lectures, student presentations of papers

Course Logistics No textbooks. Required readings are papers available online (except 3 handouts today) Office hours: before class. My contact info is on my webpage: Will (almost certainly) count for PhD elective breadth in graphics/HCI (if taken on grades)

Requirements Pass-Fail –Show up to class regularly –Present 1 (maybe 2) paper(s) –Prefer you do this rather than just sit in Grades –Attend class, participate in discussions (10%) –Present 2 (maybe 3) papers (30%) –Project (60%)

Project Wide flexibility if related to course (some ideas off main course webpage). Can be done in groups of 2-3 –Implementation/extension of one of the papers –Modeling of challenging natural object –Theoretical analysis/extension/verification –Best projects will go beyond simple implementation (try something new, some extensions) Alternative (less desirable): Summary of 3 or more papers in an area –Best projects will explore links/framework not discussed by authors, and suggest future research directions

Prerequisites Strong interest in graphics (and vision) Computer graphics experience (4160) –What if lacking prerequisites? Next slide Course will move quickly –Covering recent and current active research –Some material quite technical –Assume some basic knowledge –Many topics. Needn’t fully follow each one, but doing so will be most rewarding.

If in doubt/Lack prerequisites Material is deep, not broad –May be able to pick up background quickly –Course requirements need you to really fully understand only one/two areas (topics) –But if completely lost, won’t be much fun If in doubt, see if you can more or less follow some of papers after background reading Ultimately, your call

Assignment this week me –Name, , status (Senior, PhD etc.) –Will you be taking course grades or P/F –Background in graphics/any special comments –Optional: Papers you’d like to present FCFS Paper presenters for next week [You (may) get a one-paper reduction in load] –Oren-Nayar, Torrance-Sparrow, Koenderink-van Doorn

Questions?