introduction to hierarchical modeling and animation using

Introduction to Hierarchical Modelingand Animation using Inventor

François Faure

Grenoble Universities, INRIA, CNRS

François Faure Introduction to Hierarchical Modeling and Animation using Inventor

A graphical model

A graphical model

Composed of :geometric shapesdisplacementscolors


A graphical model

A sphere

Text file :� �# I nven to r V2.0 a s c i i

Sphere { }� �File format : Inventor V2.0 ascii

One single object with default values


A graphical model

Adding a cylinder


Sphere { }Cy l inder { }� �or, equivalently :� �# I nven to r V2.0 a s c i i

Cy l inder { }Sphere { }� �

The cylinder has default values tooThe order does not matter here


A graphical model

Tuning the parameters


Sphere {rad ius 0.1

}Cy l inder {

rad ius 0.05he igh t 1

}� �Objects have attributesPosition and orientation are notshape attributes


A graphical model

Changing the coordinate system


Sphere {rad ius 0.1

}T rans la t i on {

t r a n s l a t i o n 0 0.5 0}Cy l inder {

rad ius 0.05he igh t 1

}� �Objects are drawn in their localcoordinate system


A graphical model

Adding a cone

� �# I nven to r V2.0 a s c i i

Sphere {rad ius 0.1

}T rans la t i on {

t r a n s l a t i o n 0 0.5 0}Cy l inder {

rad ius 0.05he igh t 0.8

}T rans la t i on {

t r a n s l a t i o n 0 0.4 0}Cone {

bottomRadius 0.1he igh t 0.1

}� �Geometric transforms are combinedBasic shapes are centered at the origin of thecurrent coordinate system


A graphical model

Adding the X arrow


Sphere { rad ius 0.1 }

T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder {


}T rans la t i on { t r a n s l a t i o n 0 0.4 0 }Cone {


}

# Rotate then draw the arrow againRotationXYZ { ax is Z angle −1.5708 }





}� �

Rotate along Z


A graphical model

Adding the X arrow







}

# Rotate then draw the arrow againRotationXYZ { ax is Z angle −1.5708 }





}� �

Rotate along ZTransformations are applied in thecurrent reference frame

Need a translation to start back fromthe origin.


A graphical model

Better� �# I nven to r V2.0 a s c i i

Sphere { rad ius 0.1 }T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder {




}

# back to o r i g i n then draw againT rans la t i on { t r a n s l a t i o n 0 −0.9 0 }RotationXYZ { ax is Z angle −1.5708 }





}� �François Faure Introduction to Hierarchical Modeling and Animation using Inventor

A graphical model

Groups



DEF arrow Group {T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder {




}}

# back to the o r i g i nT rans la t i on { t r a n s l a t i o n 0 −0.9 0 }

# then r o t a t e and redrawRotationXYZ { ax is Z angle −1.5708 }USE arrow� � Groups define hierarchical

structuresNaming a group allows us to re-useit


A graphical model

Separators

Separators push/pop statevaluesSeparators leave the stateunchanged� �

# I nven to r V2.0 a s c i i


DEF arrow Separator {T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder {




}}# a u t o m a t i c a l l y back to prev ious s ta te

# then r o t a t e and redrawRotationXYZ { ax is Z angle −1.5708 }USE arrow� �

Groups “contaminate” the restof the scene and may inducedata dependency� �

# I nven to r V2.0 a s c i i


DEF arrow Group {T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder {




}}

# back to the o r i g i nT rans la t i on { t r a n s l a t i o n 0 −0.9 0 }

# then r o t a t e and redrawRotationXYZ { ax is Z angle −1.5708 }USE arrow� �


A graphical model

Colors



Ma te r i a l { d i f f u s e C o l o r 0 1 0 }DEF arrow Separator{

T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder { rad ius 0.05

he igh t 0 .8 }T rans la t i on { t r a n s l a t i o n 0 0.4 0 }Cone { bottomRadius 0.1

he igh t 0.1 }}

RotationXYZ { ax is Z angle −1.5708 }Ma te r i a l { d i f f u s e C o l o r 1 0 0 }

USE arrow� �Separators leave the stateunchanged


A graphical model

Adding the Z axis



Ma te r i a l { d i f f u s e C o l o r 0 1 0 }DEF arrow Separator{

T rans la t i on { t r a n s l a t i o n 0 0.5 0 }Cy l inder { rad ius 0.05

he igh t 0 .8 }T rans la t i on { t r a n s l a t i o n 0 0.4 0 }Cone { bottomRadius 0.1

he igh t 0.1 }}

RotationXYZ { ax is Z angle −1.5708 }Ma te r i a l { d i f f u s e C o l o r 1 0 0 }

USE arrow

RotationXYZ { ax is X angle 1.5708 }Ma te r i a l { d i f f u s e C o l o r 0 0 1 }

USE arrow� �François Faure Introduction to Hierarchical Modeling and Animation using Inventor

A graphical model

Scene graph

The scene is modeled as a tree-like structure (DirectedAcyclic Graph)Three families of rendering nodes :

Shape nodes, which represent 3D geometric objectsProperty nodes, which represent appearance and otherqualitative characteristics of the sceneGroup nodes, which are containers that collect nodes intographs


A graphical model

The Traversal state

Scene processing is performed by depth-first graphtraversalsThe drawings depend of the traversal state :

Current geometric transformationCurrent material componentsCurrent lighting modelCurrent drawing styleCurrent text fontCurrent coordinatesCurrent normalsCurrent lightsCurrent viewing specification

Separators push/pop the traversal stateSee chapter 3 of The Inventor Mentor


A graphical model

Actions

Different actions (graph traversals) can be applied to the scenegraph :

Draw, or render, the scene graphCompute a 3D bounding box for objects in the scene graphCompute a cumulative transformation matrix (and itsinverse)Write the scene graph to a fileSearch for nodesAllow objects in the scene graph to handle an eventPick objects in the scene graph along a rayTraverse the scene graph and accumulate traversal state,then perform your own action using callback functionsSee chapter 9 of The Inventor Mentor


A graphical model

Modeling the Water Molecule in C++

� �/ / Code from ‘ ‘ The Inven to r mentor ’ ’ , Jos ie Wernecke , Addison−Wesley/ / Const ruct a l l pa r t sSoGroup ∗waterMolecule = new SoGroup ; / / water molecule

SoGroup ∗oxygen = new SoGroup ; / / oxygen atomSoMater ia l ∗ r e d P l a s t i c = new SoMater ia l ;SoSphere ∗sphere1 = new SoSphere ;

SoGroup ∗hydrogen1 = new SoGroup ; / / hydrogen atomsSoGroup ∗hydrogen2 = new SoGroup ;SoTransform ∗hydrogenXform1 = new SoTransform ;SoTransform ∗hydrogenXform2 = new SoTransform ;SoMater ia l ∗w h i t e P l a s t i c = new SoMater ia l ;SoSphere ∗sphere2 = new SoSphere ;SoSphere ∗sphere3 = new SoSphere ;

/ / Set a l l f i e l d values f o r the oxygen atomr edP las t i c−>ambientColor . setValue ( 1 . 0 , 0 .0 , 0 .0 ) ;r edP las t i c−>d i f f u s e C o l o r . setValue ( 1 . 0 , 0 .0 , 0 .0 ) ;r edP las t i c−>specu larColor . setValue ( 0 . 5 , 0 .5 , 0 .5 ) ;r edP las t i c−>sh in iness = 0 . 5 ;� �


A graphical model

Modeling the Water Molecule in C++ (continued)

� �/ / Code from ‘ ‘ The Inven to r mentor ’ ’ , Jos ie Wernecke , Addison−Wesley/ / Set a l l f i e l d values f o r the hydrogen atomshydrogenXform1−>sca leFactor . setValue (0 .75 , 0.75 , 0 .75) ;hydrogenXform1−>t r a n s l a t i o n . setValue ( 0 . 0 , −1.2, 0 .0 ) ;hydrogenXform2−>t r a n s l a t i o n . setValue (1.1852 , 1.3877 , 0 .0 ) ;wh i t eP las t i c−>ambientColor . setValue ( 1 . 0 , 1 .0 , 1 .0 ) ;wh i t eP las t i c−>d i f f u s e C o l o r . setValue ( 1 . 0 , 1 .0 , 1 .0 ) ;wh i t eP las t i c−>specu larColor . setValue ( 0 . 5 , 0 .5 , 0 .5 ) ;wh i t eP las t i c−>sh in iness = 0 . 5 ;

/ / Create a h ie ra rchywaterMolecule−>addChild ( oxygen ) ;waterMolecule−>addChild ( hydrogen1 ) ;waterMolecule−>addChild ( hydrogen2 ) ;

oxygen−>addChild ( r e d P l a s t i c ) ;oxygen−>addChild ( sphere1 ) ;hydrogen1−>addChi ld ( hydrogenXform1 ) ;hydrogen1−>addChi ld ( w h i t e P l a s t i c ) ;hydrogen1−>addChi ld ( sphere2 ) ;hydrogen2−>addChi ld ( hydrogenXform2 ) ;hydrogen2−>addChi ld ( sphere3 ) ;� �


A graphical model

Scenegraph Built-in Animation Using Engines

Engines :Are part of the scene graph (can be read from file andwritten to file)Have built-in functionsAre evaluated automaticallyHave inputs fields and outputs fields of a fixed typeCan affect only other nodes or engines in a scene graph


A graphical model

A Simple Field Connection

A digital clock connected to the global field “realTime”


A graphical model

Example of Engines

Translation as a function of time

SoElapsedTime engine isconnected to realTime perdefaultSoComposeVec3f has 3scalar inputs and one 3Dvector outputThe model slidescontinuously from left toright


A graphical model

SoRotor

An embedded engine animates a rotation.


A graphical model

Frame Hierarchies

Example : a simple planetary system

sun at the center of theworld reference frame

r1(0,0, θ1) : yearly earthrotationt2(x2,0,0) : sun-earthoffsetr3(0,0, θ3) : dayly earthrotationr4(0,0, θ4) : monthly moonrotationt5(x5,0,0) : earth-moonoffset


A graphical model

Frame Hierarchies


sun at the center of theworld reference framer1(0,0, θ1) : yearly earthrotation

t2(x2,0,0) : sun-earthoffsetr3(0,0, θ3) : dayly earthrotationr4(0,0, θ4) : monthly moonrotationt5(x5,0,0) : earth-moonoffset


A graphical model

Frame Hierarchies


sun at the center of theworld reference framer1(0,0, θ1) : yearly earthrotationt2(x2,0,0) : sun-earthoffset

r3(0,0, θ3) : dayly earthrotationr4(0,0, θ4) : monthly moonrotationt5(x5,0,0) : earth-moonoffset


A graphical model

Frame Hierarchies


sun at the center of theworld reference framer1(0,0, θ1) : yearly earthrotationt2(x2,0,0) : sun-earthoffsetr3(0,0, θ3) : dayly earthrotation

r4(0,0, θ4) : monthly moonrotationt5(x5,0,0) : earth-moonoffset


A graphical model

Frame Hierarchies


sun at the center of theworld reference framer1(0,0, θ1) : yearly earthrotationt2(x2,0,0) : sun-earthoffsetr3(0,0, θ3) : dayly earthrotationr4(0,0, θ4) : monthly moonrotation

t5(x5,0,0) : earth-moonoffset


A graphical model

Frame Hierarchies


sun at the center of theworld reference framer1(0,0, θ1) : yearly earthrotationt2(x2,0,0) : sun-earthoffsetr3(0,0, θ3) : dayly earthrotationr4(0,0, θ4) : monthly moonrotationt5(x5,0,0) : earth-moonoffset


A graphical model

A Frame Hierarchy in Inventor


A graphical model

Visualizing the local coordinate system

include an external fileits content is drawn in thelocal coordinate systemwe reuse the initialexample


A graphical model

Changing the point of view

sun fixed, moving earth earth fixed, moving sun


A graphical model

Adapting a scene graph

Sun fixed, moving earthand moon

Moon fixed, moving sunand earth


A graphical model

Resources

Free implementation of OpenInventor : www.coin3d.orgLinux : install packages SoQt-dev, libsimageWindows/Mac : download and compile Coin, SoWin,simage

Additional resources onwww-evasion.imag.fr/Membres/Francois.Faure/enseignement/ressources/openinventor.html

Inventor Mentor : reference bookDeveloper documentation (doxygen-html, also onwww.coin3d.org)Code and project files of the Inventor Mentor examplesInventor Toolmaker : to extend OpenInventor


introduction to hierarchical modeling and animation using

Documents