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99 Lighting a Scene Lighting a Scene

There are four types of lighting:There are four types of lighting:– ambient lightambient light– directional lightdirectional light– point lightpoint light– spotlightspotlight

Any number of these can be added to a scene.Any number of these can be added to a scene. A shape must be set up to reflect light (see later).A shape must be set up to reflect light (see later).

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LightsLights

Java 3D Lighting ModelJava 3D Lighting Model InfluenceInfluence Different Light TypesDifferent Light Types Mixing LightsMixing Lights Material ObjectsMaterial Objects Other Coloring PossibilitiesOther Coloring Possibilities ShadowsShadows

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LightsLights

ObjectivesObjectives

Understand the Java 3D lighting system. Understand the Java 3D lighting system. Know about the different ways to give a Know about the different ways to give a

color to an object.color to an object. Recall the theory about additive light Recall the theory about additive light

mixing.mixing.

Tutorial Page 6-2

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LightsLights

Java 3D Lighting ModelJava 3D Lighting Model

There are three different reflections:There are three different reflections:– Ambient (caused by ambient light)Ambient (caused by ambient light)– Diffuse („normal“ reflection)Diffuse („normal“ reflection)– Specular (highlight reflections of polished Specular (highlight reflections of polished

material)material) No inter-object reflections in Java 3D. No inter-object reflections in Java 3D. Light sources are not visible itself.Light sources are not visible itself.

Tutorial Page 6-2

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LightsLights

InfluenceInfluence

There is no warning for leaving light out of There is no warning for leaving light out of a scene.a scene.

There is no warning for not setting a light There is no warning for not setting a light source its influencing bounds.source its influencing bounds.

Some light types have a attenuation setting. Some light types have a attenuation setting.

Tutorial Page 6-8 6-9

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LightsLights

Different Light TypesDifferent Light Types

Ambient lightAmbient lightAs if the sky was cloudy.As if the sky was cloudy.

Directional lightDirectional lightFor the virtual „sun“.For the virtual „sun“.

Point lightPoint lightFor virtual lamps.For virtual lamps.

Spot lightSpot lightVirtual spot lamps.Virtual spot lamps.

Tutorial Page 6-11 ff

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LightsLights

Mixing LightMixing Light

Why does an object appear in a certain Why does an object appear in a certain color?color?

White sphere, red and blue light -> result? White sphere, red and blue light -> result?

Tutorial Page 6-17

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LightsLights

Material ObjectMaterial Object

Color settings of the material object Color settings of the material object represent „reflection coefficients“.represent „reflection coefficients“.

Shininess is an interesting value.Shininess is an interesting value.

Tutorial Page 6-21

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LightsLights

Other Coloring PossibilitiesOther Coloring Possibilities

No lights needed, but no „shiny“ effects:No lights needed, but no „shiny“ effects:– ColoringAttributesColoringAttributes– Per-vertex color (KickCan example: class Per-vertex color (KickCan example: class

Floor).Floor).

Tutorial Page 6-23

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LightsLights

ShadowsShadows

There are no built-in shadows in Java 3D. There are no built-in shadows in Java 3D. Shadows in the tutorial are created using Shadows in the tutorial are created using

hand-made classes and polygones.hand-made classes and polygones.

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LightsLights

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Lighting ModelLighting Model

Capture from the OpenGLCapture from the OpenGL

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Lighting Model(scope)Lighting Model(scope)

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SceneGraph(Light)SceneGraph(Light)

S

BG

TG

TG

TG

S

S

S

TG

Locale

VitualUniverse object

view

sphere

environment BGL

scopeTG

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Shading ModelShading Model

Flat Shading Gouraud Shading

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MaterialMaterial

Same as OpenGLSame as OpenGL AmbientColorAmbientColor DiffuseColorDiffuseColor SpecularColorSpecularColor EmissiveColorEmissiveColor ShininessShininess

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9.1. Ambient Light9.1. Ambient Light

Ambient light has the same intensity in all locations and directions– used as a kind of 'background' lighting

in many scenes

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. Directional Light. Directional Light

Provides light shining in one direction– often used to approximate the sun

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. Point Light. Point Light Light emitted from a pointLight emitted from a point

– the intensity changes with distancethe intensity changes with distance

– often used to approximate light bulbs, often used to approximate light bulbs, candles, etc.candles, etc.

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SpotLightSpotLight

Adds direction and concentration to the Adds direction and concentration to the PointLight

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lightScene() in WrapChecker3DlightScene() in WrapChecker3D private void lightScene() /* One ambient light, 2 directional lights */ { Color3f white = new Color3f(1.0f, 1.0f, 1.0f); // Red, Green, Blue values in 0-1 range

// Set up the ambient light AmbientLight ambientLightNode =

new AmbientLight(white); ambientLightNode.setInfluencingBounds(bounds);

sceneBG.addChild(ambientLightNode);:

Lights must be givenbounds in which tooperate.

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// Set up the directional lights Vector3f light1Direction =

new Vector3f(-1.0f, -1.0f, -1.0f); // (x,y,z) left, down, backwards

Vector3f light2Direction = new Vector3f(1.0f, -1.0f, 1.0f);

// (x,y,z) right, down, forwards:

x-axis

z-axis

y-axisviewer

+

+

+

-

-

-

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DirectionalLight light1 = new DirectionalLight(white, light1Direction); light1.setInfluencingBounds(bounds); sceneBG.addChild(light1);

DirectionalLight light2 = new DirectionalLight(white, light2Direction); light2.setInfluencingBounds(bounds); sceneBG.addChild(light2);

} // end of lightScene()

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Making a BackgroundMaking a Background

private void addBackground() // A blue sky { Background back = new Background(); back.setApplicationBounds( bounds ); back.setColor(0.17f, 0.65f, 0.92f); // sky colour sceneBG.addChild( back ); } // end of addBackground()

A background can be a constant colour (as here), an image, or a geometry.

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3D Shapes3D Shapes A 3D shape is defined as a A 3D shape is defined as a Shape3D object. object.

Each Each Shape3D object has object has two node components:two node components:– Geometry

made up of coordinates made up of coordinates (vertices)(vertices)

– Appearance e.g. colour, texture, e.g. colour, texture,

transparency,transparency,materialmaterial

continued

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There are several predefined shape classes iThere are several predefined shape classes in n com.sun.j3d.utils.geometry::– Box, , Sphere, , Cone, , Cylinder

we use we use Sphere in in Checkers3D

Usually these classes are insufficient, and a Usually these classes are insufficient, and a shape's geometry must be built by connectinshape's geometry must be built by connecting vertices. g vertices.

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Shape RepresentationShape Representation

Shape?Shape?– GeometryGeometry

How to represent geometry?How to represent geometry? Polygon-based representationPolygon-based representation

– AppearanceAppearance What is the appearance?What is the appearance?

Shape3D classShape3D class

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Building GeometryBuilding Geometry

The The GeometryArray class is the parent for class is the parent for several useful geometry subclassesseveral useful geometry subclasses

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GeometryGeometryGeometryArray

GeometryStripArray

IndexedGeometryArray

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Shape ColourShape Colour

You can specify a shape's colour in three ways: – in the shape's material

used when the scene is illuminated (as here)

– in the shape's colouring attributes used when the shape is unreflecting

– in the vertices of the shape's geometry also for unreflecting shapes

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Illuminating a ShapeIlluminating a Shape

A shape will reflect light when:– the scene has lights

set up in lightScene()

– the shape has material information see the next few slides

– the shape has a geometry containing normals done automatically in predefined shapes

(Sphere, Box, etc.)

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Types of Shape ReflectionTypes of Shape Reflection

specularreflection(white)

diffusereflection(blue)

ambientreflection(blue here, but often set to black)

no shadow

no reflectionfor the floor

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MaterialMaterial

The The Material is part of a shape's is part of a shape's Appearance node component.node component.

The The Material object specifies ambient, diffu object specifies ambient, diffuse, specular, and emissive colors and a shinise, specular, and emissive colors and a shininess valueness value– emissive colour is a kind of glowing effect, but emissive colour is a kind of glowing effect, but

it does not illuminate other shapesit does not illuminate other shapes

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Creating a MaterialCreating a Material private void floatingSphere() // A shiny blue sphere located at (0,4,0) { // Create the blue appearance node Color3f black = new Color3f(0.0f, 0.0f, 0.0f); Color3f blue = new Color3f(0.3f, 0.3f, 0.8f); Color3f specular = new Color3f(0.9f, 0.9f, 0.9f);

Material blueMat = new Material(blue, black, blue, specular,25.0f); // ambient,emissive,diffuse,specular,shininess blueMat.setLightingEnable( true );

Appearance blueApp = new Appearance(); blueApp.setMaterial(blueMat); : // position the sphere: see later }

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A shape is transformed using a A shape is transformed using a TranformGroup object.object.

The three basic transformations:The three basic transformations:– translationtranslation: move the shape to a new location: move the shape to a new location– rotationrotation: rotate the shape around the X, Y, Z axes: rotate the shape around the X, Y, Z axes– scalingscaling: resize the shape : resize the shape

A A TransformGroup object is initialised using object is initialised using Tranform3D objects. objects.

TransfomationsTransfomations

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TranslationTranslation Build a shapeBuild a shape

Shape3D myShape = new Shape3D(myGeo, myApp);

TranslationTranslationTransform3D t3d = new Transform3D();t3d.set( new Vector3d(2.0, 1.0, -2.0) );

Create a transform group, set transform, add Create a transform group, set transform, add

the shapethe shapeTransformGroup tg = new TransformGroup(t3d);tg.addChild(myShape);

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RotationRotation Build shapeBuild shape

Shape3D myShape = new Shape3D(myGeo, myApp);

Rotation (around z-axis)Rotation (around z-axis)Transform3D t3d = new Transform3D();t3d.rotZ(0.785); // rotate by 45 degrees

Create a transform group, set transform, add Create a transform group, set transform, add the shapethe shapeTransformGroup tg = new TransformGroup(t3d);tg.addChild(myShape);

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RotationRotation

public BranchGroup SceneGraph(){

BranchGroup bg = new BranchGroup();

ColorCube c = new ColorCube(0.4f);

Transform3D t1 = new Transform3D();

t1.rotX(Math.PI/3.0d);

TransformGroup tg = new TransformGroup(t1);

tg.addChild(c);

bg.addChild(tg);

bg.compile();

return bg;

}

We need to change just:

Output

Scene Graph

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What about the java3d What about the java3d coordinate system?coordinate system?

2n Meters Units 87.29 Universe (20 billion light years) 69.68 Galaxy (100,000 light years) 53.07 Light year 43.43 Solar system diameter 23.60 Earth diameter 10.65 Mile 9.97 Kilometer 0.00 Meter -19.93 Micron -33.22 Angstrom -115.57 Planck length

The coordinate system is sufficient to describe a universe in excess of several hundred billion light years across, yet still define objects smaller than a proton! [check this]

It is a right handed system, in meters.

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ScalingScaling Build shapeBuild shape

Shape3D myShape = new Shape3D(myGeo, myApp);

Scaling by 1.75 in X, Y, and ZScaling by 1.75 in X, Y, and ZTransform3D t3d = new Transform3D();t3d.set(1.75);

Create transform group, set transform, add the Create transform group, set transform, add the

shapeshapeTransformGroup tg = new TransformGroup();tg.setTransform(t3d); // another waytg.addChild(myShape);

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Composite TransformationsComposite Transformations

Combine translations, rotations, and Combine translations, rotations, and

scaling.scaling.

Methods: Methods: void setTranslation( Vector3d vectorTranslation );

void setRotation( AxisAngle4d axisangleAxis );void setRotation( Matrix3d matrixRotation );void setScale( double scaleFactor );

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Positioning the SpherePositioning the Sphere

private void floatingSphere() // blue sphere located at (0,4,0) { : // set up the blue material

// position the sphere Transform3D t3d = new Transform3D(); t3d.set( new Vector3f(0,4,0)); TransformGroup tg = new TransformGroup(t3d); tg.addChild( new Sphere(2.0f, blueApp) ); // set its radius and appearance sceneBG.addChild(tg); } // end of floatingSphere()