Lighting Your World

Motivation

• By default, you have one light in the scene, attached to your head
• For more realism, you can add multiple lights
  • Suns, light bulbs, candles
  • Flashlights, spotlights, firelight
• Lights can be positioned, oriented, and colored
• Lights do not cast shadows

Using types of lights

There are three types of X3D lights:

• Point lights - radiate in all directions from a point
• Directional lights - aim in one direction from infinitely far away
• Spot lights - aim in one direction from a point, radiating in a cone

Using common lighting features

All lights have several common fields:

• on - turn it on or off
• intensity - control brightness
• ambientIntensity - control ambient effect
• color - select color

Point lights and spot lights also have:

• location - position
• radius - maximum lighting distance
• attenuation - drop off with distance

Directional lights and spot lights also have:

• direction - aim direction

Syntax: PointLight

A PointLight node illuminates radially from a point:

XML Encoding

<PointLight
    location='0.0 0.0 0.0'
    intensity='1.0'
    color='1.0 1.0 1.0'/>

Classic VRML Encoding

PointLight {
  location  0.0 0.0 0.0
  intensity 1.0
  color     1.0 1.0 1.0
}

Syntax: DirectionalLight

A DirectionalLight node illuminates in one direction from infinitely far away:

XML Encoding

<DirectionalLight
    direction='1.0 0.0 0.0'
    intensity='1.0'
    color='1.0 1.0 1.0'/>

Classic VRML Encoding

DirectionalLight {
  direction 1.0 0.0 0.0
  intensity 1.0
  color     1.0 1.0 1.0
}

Syntax: SpotLight

A SpotLight node illuminates from a point, in one direction, within a cone:

XML Encoding

<SpotLight
    location='0.0 0.0 0.0'
    direction='1.0 0.0 0.0'
    intensity='1.0'
    color='1.0 1.0 1.0'
    cutOffAngle='0.785'/>

Classic VRML Encoding

SpotLight {
  location    0.0 0.0 0.0
  direction   1.0 0.0 0.0
  intensity   1.0
  color       1.0 1.0 1.0
  cutOffAngle 0.785
}

• The maximum width of a spot light’s cone is controlled by the cutOffAngle field
• An inner cone region with constant brightness is controlled by the beamWidth field

XML Encoding

<SpotLight
    ...
    cutOffAngle='0.785'
    beamWidth='0.52'/>

Classic VRML Encoding

SpotLight {
  ...
  cutOffAngle 0.785
  beamWidth   0.52
}

Summary

• There are three types of lights: point, directional, and spot
• All lights have an on/off, intensity, ambient effect, and color
• Point and spot lights have a location, radius, and attenuation
• Directional and spot lights have a direction