1. VRML 97
Formato per la definizione di oggetti 3D. La versione VRML 1 viene da una semplificazione degli scene graphs di OpenInventor. La versione 2.0 (97) aggiunge molti nuovi nodi e modifica gran parte dei vecchi. Si tratta comunque di uno standard molto recente (Agosto 1996 per la 1.0).
I files VRML non sono eseguibili, ma files di solo testo che vengono “eseguiti” da un VRML browser. Il browser legge il file e genera un ambiente 3D interattivo. Molto usato sul WEB.
VRML 2.0

2. Ambiente Usato
I browsers VRML sono plugins di un browser HTML. Noi vedremo Cosmo Player 2.0 (della Silicon Graphics) insieme a Netscape 4.
Il browser e’ disponibile gratuitamente sul sito
Alternativa: usare WorldView (della Intervista) insieme ad Internet Explorer 4.
Informazioni dettagliate su VRML nei siti:
Sito Ufficiale VRML
Repository VRML
VRML 2.0

3. Dave Nadeau, John Moreland e Mike Heck
Tutorial
I lucidi successivi vengono da un tutorial tenuto al SIGGRAPH96 da:
Dave Nadeau, John Moreland e Mike Heck
Versione interattiva disponibile sulla mia pagina e nella directory del laboratorio. Contiene anche molti esempi ed esercizi. Originale sul WWW alla pagina:
VRML 2.0

4. What is VRML? VRML is: A text file format
A simple language for describing 3-D shapes and
interactive environments
A web standard
VRML is endorsed by:
Most 3-D graphics vendors
Most web browser vendors
VRML 2.0

5. VRML File Structure VRML files contain: The file header
Comments - notes to yourself
Nodes - nuggets of scene information
Fields - node attributes you can change
Values - attribute values
Node Names - names for reusable nodes
more. . .
VRML 2.0

6. A Sample VRML File #VRML V2.0 utf8 # A Cylinder Shape {
appearance Appearance {
material Material { } }
geometry Cylinder {
height 2.0
radius 1.5
} }
VRML 2.0

7. Defining Names for Nodes
Nodes can be named, and used
repeatedly
DEF MyCylinder Shape {
. . . }
USE MyCylinder
VRML 2.0

8. Shapes Shapes are the building blocks of a VRML world
Primitive Shapes are standard building blocks:
Box
Cone
Cylinder
Sphere
VRML 2.0

9. Shapes (2) Shape nodes describe: geometry - form, or structure
appearance - color and texture
Shape {
geometry
appearance . . . }
VRML 2.0

10. Specifying Geometry Shape geometry is built with geometry nodes
Standard, primitive geometry nodes include:
Box { }
Cone { }
Cylinder { }
Sphere { }
VRML 2.0

11. Setting Geometry Dimensions
Geometry node fields control dimensions
Box { size }
Dimensions are usually in meters, but they can be anything
Cone { height 3.0 bottomRadius 0.75 }
Cylinder { height 2.0 radius 1.5 }
Sphere { radius 1.0}
VRML 2.0

12. A Sample Primitive Shape
#VRML V2.0 utf8
Shape {
appearance Appearance {
material Material { } }
geometry Cylinder {
height 2.0
radius 1.5
VRML 2.0

13. Groups Group nodes describe:
children - a list of member nodes for the group
#VRML V2.0 utf8
Group {
children [
Shape { },
. . .
] }
VRML 2.0

14. Specifying Transforms
A Transform group node controls:
translation - position
rotation - orientation
scale - size
Transform {
translation rotation
scale children [ ] }
It applies, in a fixed order,
scale - rotation -translation
VRML 2.0

15. Appearance
The primitive shapes have a default emissive (glowing) white appearance
You can control a shape's
Shading color
Glow color
Transparency
more . . .
VRML 2.0

16. Appearance (2) Appearance nodes describe: material properties - color,
transparency, etc.
more . . .
Shape {
appearance Appearance { material }
geometry . . . }
VRML 2.0

17. Materials A Material node controls: diffuse color - main shading color
emissive color - glowing color
transparency - opaque or not
more . . .
Material {
diffuseColor
emissiveColor . . .
transparency }
VRML 2.0

18. Example Shape { appearance Appearance {
material Material { diffuseColor } }
geometry . . .
VRML 2.0

19. Grouping Nodes Shapes can be grouped to compose more complex shapes
VRML has several grouping nodes, including:
Group { }
Switch { }
Transform { }
Billboard { }
VRML 2.0

20. Group and Switch
The Group node creates a basic group. Every child node in the group is displayed
Group { children [ ] }
The Switch group node creates a switched group. Only one child node in the group is displayed. You select which child
Switch {
whichChoice 0
choice [ ] }
VRML 2.0

21. Transform and Billboard
The Transform group node creates a group with its own coordinate system. Every child node in the group is displayed
Transform {
translation . . .
rotation
scale
children [ ] }
VRML 2.0

22. Billboard
The Billboard group node creates a group with a special coordinate system. Every child node in the group is displayed. Coordinate system is turned to face viewer
Billboard { axisOfRotation children [ ] }
A rotation axis defines a pole to rotate round. Similar to a Transform node's rotation field, but no angle (auto computed)
VRML 2.0

23. A Sample Billboard Group
children [
Billboard {
axisOfRotation
children [ ... ] },
Transform { } ] }
VRML 2.0

24. Summary of Groups The Group node creates a basic group
The Switch node creates a group with 1 choice used
The Transform node creates a group with a new coordinate system
The Billboard node creates a group with a coordinate system that rotates to face the viewer
VRML 2.0

25. Components VRML files describe components of a world:
Tables, chairs, lamps, walls, floors, doors
Inlining combines files to build larger components
Rooms, buildings, neighborhoods
VRML 2.0

26. Inlining
The Inline node creates a special group. Children are read from a VRML file selected by a URL. Every child node in the group is displayed
Inline { url "table.wrl” }
Transform {
translation . . .
children [ Inline { url "chair.wrl" } ] }
VRML 2.0

27. Esempio (1)
Definizione della seguente scena
VRML 2.0

28. Esempio #VRML V2.0 utf8 Group { children [ Inline { url "table.wrl" },
Transform { translation
children DEF Chair Inline { url "chair.wrl" } },
Transform { translation
rotation children USE Chair },
Transform { translation
rotation children USE Chair },
Transform { translation
rotation children USE Chair }, ] }
VRML 2.0

29. IndexedFaceSet
Hard to build using primitives
VRML 2.0

30. Specifying Coordinates
Location of dots (points) using Coordinate node
Coordinate {
point [ , ,
. . . ] }
Three nodes have a coord field which accepts a Coordinate node
PointSet, IndexedLineSet, IndexedFaceSet
VRML 2.0

31. PointSet node A dot is drawn at each point PointSet {
coord Coordinate {
point [ ] }
No control over size of dot
Also supports color field for Color node
VRML 2.0

32. IndexedLineSet node Straight lines are drawn between points
coord Coordinate {
point [ ] }
coordIndex [
1, 0, 3, -1, . . .
] }
VRML 2.0

33. Coordinate Index Values
coordIndex [ 1, 0, 3, -1, ]
Indexes reference ordered points of coord field:
Index order is arbitrary (eg: 1, 0)
Indexes are Zero-based (eg: 0)
Can skip coordinates (eg: 0, 3)
Poly-line can be many points (eg: 1, 0, 3)
End of poly-line (eg: -1)
Multiple poly-lines (eg: . . .)
VRML 2.0

34. IndexedFaceSet node Faces are drawn within perimeter of points
coord Coordinate {
point [ ] }
coordIndex [
1, 0, 3, -1, . . . ]
VRML 2.0

35. ElevationGrid Node
Good for creating terrains, Mountain Ranges, Sea Floors and Planet Surfaces
ElevationGrid {
xDimension 3 xSpacing 1.0
zDimension 2 zSpacing 1.0
height [
0.0, -0.5, 0.0,
0.2, 4.0, 0.0 ] }
VRML 2.0

36. Texture Mapping Wrap images around shapes
Apply an image as an opaque "decal"
Apply an image with transparent "holes"
Wrap a movie's images around shapes
Add realistic appearance to shapes
VRML 2.0

37. Texture Mapping Specifics
Texture color overrides Material node color
Appearance node's texture field wraps an image around geometry
The texture can be an ImageTexture, MovieTexture, or PixelTexture
VRML 2.0

38. ImageTexture node Appearance { material Material {}
texture ImageTexture {
url "myimage.jpg" }
The ImageTexture node supports
JPEG, PNG, GIF
VRML 2.0

39. MovieTexture node Appearance { texture MovieTexture {
url "mymovie.mpg"
speed 1
loop FALSE } }
The MovieTexture nodes supports:
MPEG1-Systems and MPEG1-Video
VRML 2.0

40. PixelTexture Format
The PixelTexture node contains data stored as width, height, number of channels, followed by width*height hex values representing the image
Example: A 2x4 RGB image
PixelTexture {
image xFF0000 0x00FF00
xFFFFFF 0xFFFF00 }
VRML 2.0

41. Lights Light sources illuminate and effect shading of faces
Several types of lights available for maximum control
Lights do not cast shadows
VRML 2.0

42. Light Nodes and Fields Three different light nodes
PointLight, DirectionalLight, SpotLight
Standard fields (common to all 3) and defaults
on TRUE
intensity 1.0
ambientIntensity 0.0
color
VRML 2.0

43. Point Light Point lights have a location and glow radially
# Standard fields, plus:
location
radius 1.0
attenuation }
VRML 2.0

44. Directional Light Directional lights point in a specified direction
# Standard fields, plus:
direction }
VRML 2.0

45. Spot Light Spot lights point in a direction and focus in a cone
SpotLight { # Standard fields, plus:
location
direction
beamWidth 1.57
cutOffAngle 0.785
radius 1.0
attenuation }
VRML 2.0

46. Viewpoint Primarily used to define named camera positions
Browser will usually present a list of viewpoints using their description strings.
Browser may animate between viewpoints.
Orientation defines direction of view and "up" direction (relative to default orientation).
Viewpoint { position orientation
description "DefaultView" }
VRML 2.0

47. Events Event: A message that contains a data value
Has a specific data type, eg. SFTime
set_ event: Changes node when received
Example: set_startTime
_changed event: Sent when node changes
Example: position_changed
VRML 2.0

48. Data Types Standard VRML Data Types SFBool SFRotation / MFRotation
SFColor / MFColor SFString / MFString
SFFloat / MFFloat SFTime
SFImage SFVec2f / MFVec2f
SFInt32 / MFInt32 SFVec3f / MFVec3f
SFnode / MFNode
VRML 2.0

49. Fields and Events Each node has specific fields and events
Field: A stored value (parameter), eg. url
EventIn: An event node can receive, eg. set_url
EventOut: An event node can send, eg. url_changed
Note: ExposedField defines all three
VRML 2.0

50. Routes Route: Connects an EventOut to an EventIn
A Route is not a node!
Output type must match input type exactly
Output may connect to multiple inputs (fan-out)
Multiple outputs may connect to single input (fan-in)
Nodes must be named in order to use Routes
VRML 2.0

51. Collision Triggers Sound
ROUTE Node1.collideTime
TO Node2.startTime
Note use of DEF to name nodes
DEF NODE1 Collision { }
DEF NODE2 AudioClip { }
ROUTE NODE1.CollideTime
TO NODE2.startTime
VRML 2.0

52. Summary of Events Event: A message that contains a data value
set_ events: Change node when received
_changed events: Sent when node changes
EventIn: Specifies an event node can receive
EventOut: Specifies an event node can send
VRML 2.0

53. Sensors Sensing the user's "presence" in the world: Entering the world
Entering a region surrounding an object
Position and orientation within a region
VRML 2.0

54. The ProximitySensor Generates events when viewpoint:
Enters Region: SFTime enterTime
Leaves Region: SFTime exitTime
Moves within Region:
SFVec3f position_changed
SFRotation orientation_changed
ProximitySensor { center size }
Defines an axis-aligned region
Zero size disables the sensor
All relevant Proximity sensors generate events
VRML 2.0

55. Example: Trigger Alarm
Sound {
source DEF Alarm AudioClip { } }
DEF Car ProximitySensor {
size # size of Car
ROUTE Car.enterTime TO Alarm.startTime
VRML 2.0

56. Other Nodes that "Sense" the Viewer
LOD: Distance to viewpoint (no explicit events)
VisibilitySensor: Visibility of a region.
events: isActive, enterTime, exitTime
Collision: Collision of viewer with objects.
event: SFTime collideTime
VRML 2.0

57. TouchSensor Events Pointer is on geometry: SFBool isOver
Button press/release:
SFBool isActive
SFTime touchTime (on ButtonUp)
Pointer dragged over geometry:
SFVec3f hitPoint_changed
SFVec3f hitNormal_changed
SFVec2f hitTexCoord_changed
VRML 2.0

58. Other Nodes That "Sense" the User
Anchor: Click on children (causes implicit action)
CylinderSensor: Maps motion to rotation around sensor's Y axis
PlaneSensor: Maps motion to translation in sensor's XY plane
SphereSensor: Maps motion to general rotation around center of sensor
VRML 2.0

59. Summary of Sensors Sensors are not grouping nodes
Trigger on geometry defined by sibling nodes
When geometry overlaps, closest object is used
Sensor "lowest" in the graph sends the event
Multiple sensors may send "simultaneous" events
Use these sensors to detect user actions.
Use their events to start and stop animations.
Also for simple dragging, rotating objects.
VRML 2.0

60. Time A TimeSensor node is similar to a stop watch (sorta)
You control the start time, stop time, and cycle length
The sensor generates events while it is running
You ROUTE events to change node fields
VRML 2.0

61. Time Sensors TimeSensor nodes describe:
start and stop time - when to run
cycle interval time - how long a cycle is
looping - whether or not to repeat
cycles
TimeSensor {
cycleInterval 4.0 loop FALSE
starTime 0.0 stopTime 1.0 }
VRML 2.0

62. Timer Input Events Can create continuously running timmers:
loop TRUE stopTime < startTime
Can run one cycle then stop
loop FALSE stopTime < startTime
Can run until stopped, or after cycle is over
loop TRUE or FALSE stopTime >= startTime
The set_startTime input event:
Sets when the timer should start
The set_stopTime input event:
Sets when the timer should stop
VRML 2.0

63. Timer Cycles The first cycle starts at the start time
The cycle interval is the length (in seconds) of the cycle
Each cycle varies a fraction from 0.0 to 1.0
If loop is FALSE, there is only one cycle, otherwise the timer may cycle forever
VRML 2.0

64. Timer Output Events The isActive output event:
Outputs TRUE at timer start
Outputs FALSE at timer stop
The fraction_changed output event:
Outputs values from 0.0 to 1.0 during a cycle
Resets to 0.0 at the start of each cycle
VRML 2.0

65. A Sample Time Sensor DEF Monolith1Timer TimeSensor {
cycleInterval 4.0 loop FALSE
startTime 1.0 stopTime 0.0 }
ROUTE Monolith1Touch.touchTime
TO Monolith1Timer.set_startTime
ROUTE Monolith1Timer.fraction_changed
TO Monolith1Light.set_intensity
VRML 2.0

66. Summary of TimeSensors
The TimeSensor node's fields control:
Timer start and stop times
The cycle interval
Whether the timer loops or not
The sensor generates:
isActive events at start and stop
fraction_changed events while running
VRML 2.0

67. Interpolators To animate the position of a shape you specify:
A list of key positions for a path
An interpolator computes intermediate positions for you
You specify key values (like positions) along a path
Key values have two components
A value (such as a position)
A key fraction (usually between 0.0 and 1.0)
VRML 2.0

68. Interpolation Interpolation fills in values between your key values:
Time Position Time Position
PositionInterpolator nodes describe:
keys - key fractions
values - key positions
PositionInterpolator { key [ 0.0, ]
keyValue [ , ] }
VRML 2.0

69. Position Interpolator Events
The set_fraction input event:
Sets the current fraction (usually 0.0 to 1.0) along the key path
The value_changed output event:
Outputs the position along the path each time the fraction is set
DEF Stair1Path PositionInterpolator {
key [ 0.0, ] keyValue [ , . . .] }
ROUTE Stair1Timer.fraction_changed TO Stair1Path.set_fraction
ROUTE Stair1Path.value_changed TO Stair1.set_translation
VRML 2.0

70. Other Interpolators You can also interpolate: Rotations Colors
Coordinates
Normals
Scalars
VRML 2.0

71. Format of Interpolators
All Interpolators use keys for key fractions.
OrientationInterpolator nodes describe:
values - key rotations (axis and angle)
ColorInterpolator nodes describe:
values - key colors (red, green, blue)
CoordinateInterpolator nodes describe:
values - key coordinate lists (X,Y,Z lists)
NormalInterpolator nodes describe:
values - key normal lists (X,Y,Z lists)
ScalarInterpolator nodes describe:
values - key scalars (used for anything)
VRML 2.0

72. Scripts
Many actions are too complex for built-in sensors, interpolators, shapes, etc.
Computed animation paths (eg. gravity)
Algorithmic shapes (eg. fractals)
Collaborative environments (eg. games)
You can write program scripts in Java, JavaScript, etc, that:
Accept event inputs
Generate event outputs
Read and write fields
VRML 2.0

73. Program Script Use Script nodes include:
url - the program script to use
Script { url "circle.class” or… url "circle.js” or...
url "javascript: ...” }
Script nodes also declare:
fields and events - the program script interface
Each has a name and data type
Fields have an initial value
Script { field SFFloat cycles 1.0
eventIn SFFloat set_fraction
eventOut SFVec3f position_changed }
VRML 2.0

74. Proto You can create new node types that encapsulate: Shapes Sensors
Interpolators Scripts
anything else . . .
This creates high-level nodes
Robots, menus, new shapes, etc.
PROTO declares a new node type:
name - the new node type name
fields and events - interface to the prototype
VRML 2.0