10: building environments

generation

cortona: displays in status bar (right click / Preferences / Display Frame Rate / frames per second)
measure in busy / complex area of scene

use fewer polygons
- merge coplanar polys
- use poly reduction tools
- avoid primitives
- consider texture over geometry
- use textures in place of Text{}
consider texture in place of lighting [»]
consider colored polys in place of texture
consider colored polys and grayscale texture in place of full color texture
make use of geometry hints: ccw, solid, and convex (use default TRUE if possible)

never render more than necessary
use LOD{} for environments, with 5 levels:
[empty] [full-poly] [lo-poly] [texture] [empty] close ................................. distant
alternatively, use ProximitySensor{}, Script{}, and Switch{} for more arbitrary control
consider Billboard{} in place of geometry, especially for cylindrical or spherical objects
use Anchor{} to break world into parts that are loaded only on demand

use fewer nodes
- combine multiple IndexedFaceSets into one
- employ DEF and USE liberally
bounding boxes
- a free culling tool– use it
- mostly auto-calculated, except for external geometry: Inline{}, EXTERNPROTO
consider spatial arrangement of scene in file– don't place disparate objects in same group
break monolithic objects into multiple parts so engine can selectivley draw visible portions
model environments with obstructed lines of sight to allow scene culling
build consistent environments; avoid 'hotspots':
- multiple high LOD
- lots of simultaneous texture/geometry loading
- multiple expensive features: animations/collision/lights/sensors

reduce texture memory usage
- use low-res texture files, especially for distant or small objects
- merge individual textures into single texture
- DEF ImageTexture node and USE it for all Appearances needing access to sub textures
use minimum number of lights
- choose PointLight{} over SpotLight{}
- choose DirectionalLight{} over PointLight{}
- choose texture over DirectionalLight{}
minimize fill area
- embed vrml file into html page and use smallest feasible window
minimize viewable volume by setting NavigationInfo's visibilityLimit as close as feasible
use Fog{} to obscure pop-up of distant clipped geometry
turn off collisions
- use a Collision{} node:
  "If there are no Collision nodes specified in a scene, browsers shall detect collision with all objects during navigation"
- consider proxies when collision is required

very important for modem distribution, still relevant with CDs, never hurts to load quickly
be aware of audience's attention span:

acceptable response times

first reaction to scene request <3s

immediate surroundings loaded <30s
immediate, but partial loading is often prefered to comlete but delayed loading
Inline{} (with bounding box) can delay additional downloading until absolutely necesary
start initial viewer position inside small room and inline rest of world to minimize initial download
maximize instancing (DEF / USE)
choose Text{} over equivalent hi-res texture
choose primitives over IndexedFaceSet{}
choose ElevationGrid{}, Extrusion{}, Script{} over IndexedFaceSet{} for geometry
choose quadrilateral over triangular polys
- fewer indices, tcoords, normals
- note: no performance benefit, since quads will be triangulated by engine
reduce numerical precision, remove white space, commas, and leading zeroes
gzip vrml file
consider two-phase development:
1. human readable (ascii, white space, inlines, externprotos, etc.)
2. compressed / published (gzip, no whitespace, no externals)

acceptable response times
	first reaction to scene request	`<3s`
	immediate surroundings loaded	`<30s`