Real-Time High Quality Rendering

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Real-Time High Quality Rendering

• COMS 6160 Fall 2004, Lecture 1
• Ravi Ramamoorthi

http//www.cs.columbia.edu/ravir/6160
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Motivation

• Today, we create photorealistic computer graphics
• Complex geometry, realistic lighting, materials,
  shadows
• Computer-generated movies/special effects
  (difficult to tell real from rendered)
• But algorithms are very slow (hours to days)

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Real-Time Rendering

• Goal is interactive rendering. Critical in many
  apps
• Games, visualization, computer-aided design,
• So far, focus on complex geometry
• Chasm between interactivity, realism

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Evolution of 3D graphics rendering

• Interactive 3D graphics pipeline as in OpenGL
• Earliest SGI machines (Clark 82) to today
• Most of focus on more geometry, texture mapping
• Some tweaks for realism (shadow mapping, accum.
  buffer)

SGI Reality Engine 93 (Kurt Akeley)
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Offline 3D Graphics Rendering

• Ray tracing, radiosity, photon mapping
• High realism (global illum, shadows, refraction,
  lighting,..)
• But historically very slow techniques
• So, while you and your childrens children are
  waiting for ray tracing to take over the world,
  what do you do in the meantime? Real-Time
  Rendering

Pictures courtesy Henrik Wann Jensen
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New Trend Acquired Data

• Image-Based Rendering Real/precomputed images as
  input
• Also, acquire geometry, lighting, materials from
  real world
• Easy to obtain or precompute lots of high quality
  data. But how do we represent and reuse this for
  (real-time) rendering?

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5 years ago

• High quality rendering ray tracing, global
  illum., image-based rendering (This is what a
  rendering course would cover)
• Real-Time rendering Interactive 3D geometry with
  simple texture mapping, maybe fake shadows
  (OpenGL, DirectX)
• Complex environment lighting, real materials
  (velvet, satin, paints), soft shadows, caustics
  often omitted in both
• No COMS 6160 Realism, interactivity at cross
  purposes

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Outline of Lecture

• Background
• Motivation, effects for high quality real-time
  rendering
• Recent technological, algorithmic developments
• Preview of results currently possible
• Logistics of course

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High quality real-time rendering

• Photorealism, not just more polygons
• Natural lighting, materials, shadows
• Interiors by architect Frank Gehry. Note
  rich lighting, ranging from localized sources to
  reflections off vast sheets of glass.

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High quality real-time rendering

• Photorealism, not just more polygons
• Natural lighting, materials, shadows
• Real materials diverse and not easy to
  represent by simple parameteric models. Want to
  support measured reflectance.

Peacock feather
Glass Star (courtesy Intel)
Glass Vase
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High quality real-time rendering

• Photorealism, not just more polygons
• Natural lighting, materials, shadows
• Natural lighting creates a mix of soft diffuse
  and hard shadows.

small area light, sharp shadows
soft and hard shadows Ng et al. 03
Agrawala et al. 00
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Demo

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Applications

• Entertainment Lighting design
• Architectural visualization
• Material design Automobile industry
• Realistic Video games
• Electronic commerce

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Outline of Lecture

• Background
• Motivation, effects for high quality real-time
  rendering
• Recent technological, algorithmic developments
• Preview of results currently possible
• Logistics of course

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5 years ago

• High quality rendering ray tracing, global
  illum., image-based rendering (This is what a
  rendering course would cover)
• Real-Time rendering Interactive 3D geometry with
  simple texture mapping, maybe fake shadows
  (OpenGL, DirectX)
• Complex environment lighting, real materials
  (velvet, satin, paints), soft shadows, caustics
  often omitted in both
• No COMS 6160 Realism, interactivity at cross
  purposes

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Today

• Vast increase in CPU power, modern instrs (SSE,
  SIMD, )
• Real-time raytracing techniques are possible
• 4th generation of graphics hardware is
  programmable
• (First 3 gens were wireframe, shaded, textured)
• Modern nVidia, ATI cards allow vertex, fragment
  shaders
• Great deal of current work on acquiring and
  rendering with realistic lighting, materials
  Especially at Columbia
• Goals of COMS 6160 Understand these new ideas
  for high-quality rendering, and recent literature
  (last 5 years)
• (This is not a course about real-time rendering
  with complex geometry. It is primarily about
  high quality shading effects)

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Outline of Lecture

• Background
• Motivation, effects for high quality real-time
  rendering
• Recent technological, algorithmic developments
• Preview of results currently possible
• Programmable graphics hardware
• Precomputation-based methods
• Interactive RayTracing
• Logistics of course

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Programmable Graphics Hardware

• Nvidia dusk demo http//www.nvidia.com/object/demo
  _dusk.html

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Precomputation-Based Methods

• Static geometry
• Precomputation
• Real-Time Rendering (relight all-frequency
  effects)
• Involves sophisticated representations, algorithms

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Relit Images
Ng, Ramamoorthi, Hanrahan 04
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Video Real-Time Relighting
Followed by demo with real-time relighting with
caustics
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Interactive RayTracing

• Advantages
• Very complex scenes relatively easy (hierarchical
  bbox)
• Complex materials and shading for free
• Easy to add global illumination, specularities
  etc.
• Disadvantages
• Hard to access data in memory-coherent way
• Many samples for complex lighting and materials
• Global illumination possible but expensive
• Modern developments Leverage power of modern
  CPUs, develop cache-aware, parallel
  implementations

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Interactive Ray-Tracing Video
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Outline of Lecture

• Background
• Motivation, effects for high quality real-time
  rendering
• Recent technological, algorithmic developments
• Preview of results currently possible
• Logistics of course

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Course Goals, Format

• Goal Background and current research on
  high-quality real-time rendering in computer
  graphics
• Columbia is one of the best places for this!!
• Format Alternate lectures, student presentations
  of papers
• http//www.cs.columbia.edu/ravir/6160/

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Course Logistics

• No textbooks. Required readings are papers
  available online (except 2 handouts today)
• The book Real-Time Rendering (2nd ed) by Moller
  and Haines may be helpful (though we will not
  follow it closely)
• Office hours before class. My contact info is
  on my webpage http//www.cs.columbia.edu/ravir
• Counts for PhD elective breadth in graphics/HCI,
  MS elective for vision/graphics, BS elective etc.

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Requirements

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

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Project

• Wide flexibility if related to course. Can be
  done in groups
• Default Implement (part of) one of papers and
  produce an impressive real-time high quality
  rendering demo
• See/e-mail me re ideas
• Best projects will go beyond simple
  implementation (try something new, some
  extensions)
• Alternative (less desirable) Summary of 3
  papers in an area
• Best projects will explore links/framework not
  discussed by authors, and suggest future research
  directions

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Prerequisites

• Strong interest in graphics, rendering
• 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. Neednt fully follow each one, but
  doing so will be most rewarding.

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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, wont be much fun
• If in doubt, see if you can more or less follow
  some of papers after background reading
• Ultimately, your call

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Assignment this week

• E-mail me (ravir_at_cs)
• Name, e-mail, status (Senior, PhD etc.)
• Will you be taking course grades or P/F
• Background in graphics/any special comments
• Optional Papers youd like to present FCFS
• Paper presenters for next week You (may) get a
  one-paper reduction in load
• Hardware Geometry Engine, Reality-Engine

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Questions?