IMM2202 Interactive Multimedia Development 3 3D animation...digital audio...digital video

1
MUL242 3d modelling animation
07
Rendering
2
this lecture...

• this lecture will look at...
• Rendering
• what is it?
• rendering models
• Bringing it Together
• Models
• Surfaces
• Animation
• Sound
• Lighting
• Cameras
• Project Management

3
rendering

• the rendering process involves giving objects
  shading via a number of different methods
• each pixel is rendered by considering the
  interaction of an objects surfaces and light
  sources to derive its colour
• colour images are typically 32bit, greyscale are
  8bit...
• the time taken to calculate the image is the same
• the memory requirement is less in greyscale
• 32bit rendered images include an 8bit alpha
  channel
• 24bits colour alpha channel for
  matting/compositing
• rendering algorithms are procedures used by a
  particular program to generate an image from the
  view of a modelled world

4
rendering
24 bits (888 RGB) 8 bits (Alpha) 32 bits.
Think of the possibilities!
5
ray casting

• the colour of each pixel is typically calculated
  using a process called ray-casting
• the ray casting algorithm casts a single ray
  through each pixel. If the ray strikes a surface,
  the colour of the surface is calculated and
  assigned to the pixel
• but... how is colour calculated?

6
shading models

• shading models work in tandem with raycasting
  renderers to calculate the shading of a
  particular point on a surface and to determine
  the colour of a pixel based upon
• lights in a space
• light shining on objects
• light bouncing on objects from other objects
• shading of objects based upon their surface
  properties
• all shading models are approximations the better
  the approximation the better the image and the
  longer it takes to render

7
shading models

• faceted shading
• uses the assumption that a surface is the same
  colour across its entire face
• colour is calculated by using the surface normal
  to determine the direction of the surface
  relative to lighting
• surfaces facing a light are brighter than those
  facing away
• using the surface normal, flat surfaces render OK
  but curved surfaces require many normals in order
  for a correct approximation to take place
• Bezier-based modellers convert curved surfaces
  into patches in order to render using facets

8
smooth shading

• smooth shading algorithms take the change in
  surface normals across a surface into account
• Gouraud shading (Henri Gouraud)
• process...
• calculates the average surface normal at each
  vertex
• uses the average to calculate a colour at each
  vertex
• interpolates colour between corners
• produces good shading but generates a polygonal
  structure at the edges

9
smooth shading

• Phong shading (Bui Tuong Phong)
• calculates the average surface normal at each
  vertex
• uses the average to interpolate surface normals
  across a surface
• interpolates colour between the new normals
  across a surface
• generates much better images than Gouraud but
  also takes longer
• raycasting algorithms have a major limitation in
  that they only deal with every object in a scene
  as if it existed in isolation.
• casting shadows, transparency and reflection are
  all effects that require the effect of multiple
  objects to be calculated

10
ray tracing

• ray tracing takes into account all objects in a
  scene simultaneously by more accurately
  simulating the real world
• a specific point on a surface is affected by
  light falling onto the surface from the
  environment via reflection many light rays
  affect every point on a surface.

11
ray tracing

• ray tracing traces the rays of light backward
  through a model to determine how the image should
  appear
• if the light ray comes from a surface, the
  renderer then calculates where the light that
  reflected off that surface originated and hence
  all the objects which it bounced off or passed
  through.
• eg. the colour of the cylinder is influenced by
  the colour of the cube, the cone and the space
  around the cube

12
ray tracing

• can render almost any effect, true reflectivity,
  refractive transparency and shadows
• very computationally expensive...but results are
  brilliant
• problems
• shadows are sharp
• diffuse reflection of light between surfaces
• eg. holding a red card in front of a white wall
  should cause a pink hue to appear on the wall
• radiosity does this but is REALLY SLLLOOOOWWW!!!

13
Radiosity Caustics

• Diffuse reflected light is referred to in CG
  terminology as radiosity.
• light coming from any source will touch a surface
  of some kind, then part of that light will
  reflect away, perhaps touching another surface
  and reflecting again.

14
Caustics

• Caustics is the focusing of light due to
  reflection or refraction onto another surface so
  as to cause areas of intense illumination.

15
bringing it all together

• 3D development is a collaborative venture
  involving
• Project Managers
• Scriptwriters
• Graphic Designers
• 3D artists
• Modellers
• Surface artists
• Lighting Designers
• Cinematographers
• Animators

16
SHREK - Technical Credits

• Production Design by
• James Hegedus  
•  
• Art Direction by
• Guillaume Aretos (II)  
• Douglas Rogers  
•  
• Costume Design by
• Isis Mussenden  
•  
• Production Management
• Mitchell Ferm .... production supervisor for
  technology
• Kate Swanborg .... production manager Los
  Angeles preproduction
• Triva von Klark .... production manager
•  
• Art Department

17
SHREK - Technical Credits (cont)

• Hugh Waddell .... adr supervisor
• Wade Wilson (II) .... sound designer
  co-supervisor 2002 Imax re-release version
• sound designer editor
• Visual Effects by
• Victoria Alonso .... senior unit production
  manager Los Angeles preproduction
• Ken Bielenberg .... visual effects supervisor
• Christian Cunningham .... technical director
• Nickson Fong .... digital artist Dreamworks
  SKG, LA crew
• Ben Gunsberger .... lighting animator
• Albert Hastings .... digital layout/character
  setup
• Lee Lanier .... digital artist
• Bert Poole .... digital artist Senior Lighting
  Animator
• Bill Seneshen .... effects lead cloth
  simulation
• Susan Thayer .... digital artist additional
  effects
• Carlos A. Vidal .... digital artist senior
  technical director
•  
• Other crew
• John Bell (II) .... orchestrator

18
SHREK - Technical Credits (cont)

• Raman Hui .... supervising animator
• Ethan Hurd .... animator
• Danny Jacobs (II) .... musician guitar
• Christopher Knights .... first assistant film
  editor
• Boris Kossmehl .... animator
• Eric Lessard .... animator
• Philip K. Livingston Jr. .... production
  assistant
• Ladd McIntosh .... orchestrator
• Walling C. Michael .... render wrangler
• Marc Miller (V) .... render assistant
• Yvonne S. Moriarty .... orchestrator
• Christine M. Norton .... assistant to producer
• Jessica Nourse .... singing voice Cameron Diaz
• Elisa Pensler-Gabrielli .... adr loop group
• Emmanuel Roth .... animator
• Steven Sorensen (III) .... render assistant
• Allen Stetson .... render assistant
• Drew Stewart .... production assistant
• James C.J. Williams .... title designer end
  titles

• Jobs include
• Set Designers
• Storyboard Artists
• Clothing Designers
• Render Wrangers!

19
Project Management

• Essential to Successful Completion of any large
  Multimedia project
• Need to Monitor allocation of resources
• Time
• Budget
• Talent
• Need to Promote
• Communication
• Collaboration
• Creativity

20
Workshop

• Surfacing
• Rendering
• Rule of thirds
• Camera zoom
• Motion blur
• Depth of field
• Assignment workshop