lights in the phong model
Download
Skip this Video
Download Presentation
Lights in the Phong Model

Loading in 2 Seconds...

play fullscreen
1 / 17

Lights in the Phong Model - PowerPoint PPT Presentation


  • 63 Views
  • Uploaded on

Lights in the Phong Model. 1. How to compute these?. 2. What are these?. Light source direction: . Look around you … The light in Seattle: Indirect background, … ambient Sun light: Direct, very far away coming from a constant direction (independent of where you are)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Lights in the Phong Model' - robyn


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
lights in the phong model
Lights in the Phong Model

1. How to compute these?

2. What are these?

light source direction
Light source direction:
  • Look around you …
  • The light in Seattle: Indirect
    • background, … ambient
  • Sun light: Direct, very far away
    • coming from a constant direction(independent of where you are)
  • Light bulb at home: Direct
    • closer, shines from a fixed point
  • Light from the projector/desk lamp
    • How would you describe this?

credit: http://mynasadata.larc.nasa.gov/Radiation_Explanation.html

credit: http://www.truebeyonddesign.com/products-page/

http://www.apartmenttherapy.com/ny/lighting/best-product-tolomeo-desk-lamp-001066

what is ambient light
What is Ambient Light?
  • Not in the real world!
  • Implementation dependent!
    • constant color added to illumination results
    • Maya scene file

Rendered image

Ambient light

Material Property

what about the sun
What about the Sun?
  • How would you describe the incoming light source for this scene?

http://www.planetware.com/picture/kansas-cottonwood-falls-tallgrass-prairie-national-preserve-flint-hills-national-prairie-us-ks108.htm

directional light
Directional Light
  • Direction is:
  • No position!! (where is the Sun?)
  • Light has no geometry and does not show up in final rendered image
  • Planes looks … flat 
  • Maya Scene

Rendered image

Directional Light

what about the light bulb
What about the Light Bulb?
  • How would you describe the light source of these scenes?

http://companyofburninghearts.wordpress.com/2010/03/18/mystic-clusters/

http://home.cogeco.ca/~richardastro2/

point light
Point Light
  • Position ()
  • For every visible position ()
      • is unique!
  • Illumination is a function of relative position to lights!
  • Maya Scene

Different vector for each visible point

Point Lights

Rendered image

now my desk lamp
Now, my desk lamp
  • How would you describe the light source of these scenes?

http://www.how-to-refinish-hardwood-floors.wirze.com/

http://agreenliving.org/tag/concept-design/

http://www.mackayphotography.co.uk/light_pollution.htm

http://0.tqn.com/d/drawsketch/1/0/N/J/eggsetup.jpg

spot light
Spot Light
  • Direction + Position:
    • Pointing direction
    • As in point light, for each visible point is unique!
    • Cone angle (θ) defines illumination range

θ

Different vector for each visible point

slide10

Maya Scene

Cone boundaries

Rendered image

spotlight bounds
Spotlight bounds

Illumination at this point is

  • Position:
  • Main direction
  • : cone angle
  • θ: regions of full illumination
  • angle to position for illumination
  • If θ< < Illumination drops off according to:

θ

Region: fully illuminated

Penumbra Region: gradual drop off

drop off behavior
Drop off behavior

P<1

p=0.1

P>1

p=0.2

Drop off p=1

p=20

p=30

slide13

scene

No drop off

Penumbra region

implement penumbra region
Implement Penumbra Region
  • For a visible position:
    • cos(

If (cos( > cos( // <

Full illumination

else if (cos() < cos()) // >

no illumination

else

Penumbra region

θ

A visibleposition

distance attenuation
Distance Attenuation
  • Illumination is a function of
      • d = distance between light and visible position!!
  • Physics tells us
  • Did not follow physics in the rest of the model!
    • WAY too dark!!
  • Generally:

d

how about
How about ?
  • Let user specify each of thecomponents!

OpenGL:

Maya:

Our ToyRayTracer:

general form of phong
General form of Phong

Our Ray Tracer implements:

ad