H331: Computer Graphics - PowerPoint PPT Presentation

Loading...

PPT – H331: Computer Graphics PowerPoint presentation | free to view - id: 1ad1-M2JjN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

H331: Computer Graphics

Description:

Hollywood solution light props. Light props, light tricks ... Hollywood solution compositing. 16. The CG solution fake lights. 17. The CG solution bend light ... – PowerPoint PPT presentation

Number of Views:75
Avg rating:3.0/5.0
Slides: 24
Provided by: Philip5
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: H331: Computer Graphics


1
H331 Computer Graphics
  • http//www.cs.kuleuven.ac.be/graphics/H331/Phili
    p Dutré
  • Department of Computer Science
  • Wednesday, April 30

2
Production Rendering
  • Making movies
  • Images portray and accent the story
  • Cheating physics to make images less boring
  • Image will be seen very large by millions of
    people
  • No artifacts please
  • Deadlines cannot be broken
  • Better be fast, robust, predictable

3
Live action movies
  • They are NOT photographs of real scenes
  • Have to combine virtual and real

4
Issues in image synthesis
  • Efficiency
  • How much does it take for the machine?
  • Control
  • How hard is it to render the image for a person?
  • Fidelity
  • How faithful is the picture to what I have in
    mind?

5
Production requirements
  • Large amount of high quality geometry
  • Arbitrary programmable shading
  • Limited time memory
  • No artifacts (aliasing, tesselation, noise,
    cracks, numerical instability)
  • Mixed rendering algorithms (scanline, raytracing,
    volume rendering)
  • Robustness

6
Some numbers
  • 2000x1800 _at_ 36-100 samples/pixels
  • 120,000 frames
  • Not counting trials, mistakes, multiple elements
  • Input geometry per frame 1 GB
  • Input texture per frame 1-10 GB
  • Average cost 4 hours, 256-512 Mb
  • Roughly 50 visibility, 50 shading

7
Numbers and money
  • Renderfarm
  • 100 Sun boxes with 14GB memory
  • Approximate cost 10M (12 of a movie)
  • Cannot afford slow rendering!

8
PIXAR PRMan
  • Strenght
  • Really good antialiasing
  • Really good motion blur
  • High level surface primitives
  • Cheap displacement maps
  • Flexibility/Robustness
  • Physical light transport?

9
Ray tracing
  • Yes, they do it moderately
  • Glad they do it only occasionally
  • Normally raytrace only hand-simplified versions
    of the scenes

10
Ray tracing
11
Control
12
The typical problem
Make this side less satured
Make this corner pinker
Make this shadow sharper
Make this shadow blurrier
13
Hollywood solution ? light props
  • Light props, light tricks

14
Hollywood solution ? compositing
15
Hollywood solution ? compositing
16
The CG solution ? fake lights
17
The CG solution ? bend light
Physical light
18
The CG solution ? bend light
Physical light
Movie light
19
Light tells a story
20
Hard issues with Rendering
  • Production requirement
  • Flexibility
  • Robustness
  • Control
  • Mixing with live action footage
  • Cant afford to change the WORKFLOW!!!

21
True production problems
  • Modeling
  • Animating
  • Lighting

22
What would they pay you for?
  • Time/memory requirements
  • Automation/Control
  • Skilled lighters do better than GI
  • Too many lighters need better tools
  • Quality issues
  • Raytracing is VERY artifact prone, but simple
  • Cheating physics better

23
Reality is nice, but the art director wants the
shadow to be blue and the motion blur streak to
be longer and the wagon wheals to strobe like an
old movie. Every aspect of the image must be
adjustable for artistic interpretation, even when
doing so violates physics, mathematics and common
sense. Larry Gritz
About PowerShow.com