04: surfaces & sound

surface nodes

Appearance{} : the place to define materials and textures
Material{} : provides parameters to control surface properties of the shape
example: [»]

lighting nodes

DirectionalLight{} : straight parallel beams simulate a distant source [»]
PointLight{} : rays emanate from a central point, like an exposed bulb [»]
SpotLight{} : casts a cone of light [»]

vrml lighting model

ideally, lighting values would be calculated per pixel (Phong shading). Most commonly, though, browsers calculate lighting values at vertices, and interpolate them across the face of a polygon (Gouraud shading). This has significant implications for hilights:

vertices and light quality [»]
vertices and specular quality [»]

lighting considerations

if the browser sees diffuseColor, ambientIntensity, and specularColor all set to 0, it should exclude the shape from any lighting calculations and render it solely in its emissive color
if Gouraud shading, better lighting = more vertices + smaller polygons
light mixes via multiplication; consider red * blue: (1 0 0) * (0 0 1) = (0 0 0)
avoid hotspots where many lights illuminate the same vertices
in terms of cpu cost, directional lights are cheapest, then point lights, then spot lights
directional lights are scoped by grouping nodes
point and spot lights have radius fields to limit their impact on the scene
the vrml specification only requires browser support for eight simultaneous lights

lighting examples

additive color mixing [»]
light and surface color mixing [»]
scoping directional lights [»]
faking shadows [»]

sound nodes

Sound{} : orients and shapes the sound space
AudioClip{} : the actual sound and its pitch
cortona will play mp3, wav, midi

visualizing sound

two ellipsoids; within the inner limit volume is 100%. Beyond the outer limit volume is 0%. Between the inner and outer limits, volume changes linearly from 100% to 0%:

ambient sound

to create sound that can be heard everywhere in the scene regardless of position or orientation (like a movie sound track):

spatialize = FALSE
loop = TRUE
inner sound ellipsoid = outer sound ellipsoid = bounding dimensions of scene

directional sound

to add sound effects that should seem attached to an object or place in the scene:

spatialize = TRUE
loop = FALSE
inner sound ellipsoid is just big enough to fit the object and a listener
outer sound ellipsoid is as big as the sound should carry
direction should be specified so sound emanates properly

sound considerations

avoid hotspots where too many sounds overlap
make ellispoinds as small as practical
most vrml browsers can only play 6-8 simultaneous sounds
spatialization costs extra cpu cycles
in vrml, pitch and duration are directly linked
mp3s may be problematic with spatialization

sound examples

the basics [»]
sound vista [»]
pitch and duration [»]
moving sounds [»]
reactive sounds [»]