//load or do something to the image here //wrap the BufferedImage in an ImageComponent2D ImageComponent2D imageComponent2D = new ImageComponent2D( ImageComponent2D.FORMAT_RGB, bufferedImage); imageComponent2D.setCapability( ImageComponent.ALLOW_IMAGE_READ ); imageComponent2D.setCapability( ImageComponent.ALLOW_SIZE_READ ); //create the Raster for the image m_RenderRaster = new Raster( new Point3f( 0.0f, 0.0f, 0.0f ), Raster.RASTER_COLOR, 0, 0, bufferedImage.getWidth(), bufferedImage.getHeight(), imageComponent2D, null ); m_RenderRaster.setCapability( Raster.ALLOW_IMAGE_WRITE ); m_RenderRaster.setCapability( Raster.ALLOW_SIZE_READ ); //wrap the Raster in a Shape3D Shape3D shape = new Shape3D( m_RenderRaster ); 8.4.2 Retrieving scene depth components using a Raster The other, more unusual, application for a Rasteris to use it to retrieve the depth components of the 3D scene. These are stored in the Z-buffer, a multibyte array that stores the depth into the scene for each rendered pixel. The depth to the first occurrence of geometry is stored in the Z-buffer, and floating point values are scaled such that the closest value to the user is zero while the farthest value is one. Querying the Z-buffer directly is quite uncommon, but may be useful for such application-specific functionality as hit testing or rendering. The following example illustrates overriding the Canvas3D postSwapmethod to retrieve the contents of the Z-buffer for the scene using a Rasterobject. The Z-buffer Rasteris then used to dynamically update an image Rasterso that the depth components can be rendered graphically. The output from the RasterTestillustrating this technique is shown in figure 8.9. Figure 8.9 Two frames from RasterTest. Each frame contains a rotating cube and a Raster displaying the depth components of the entire frame. The Raster is visible because it also has a depth component 117
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8.2.6 Primitives and the geometry cache The Primitive-derived classes use a very simplistic cache to minimize the CPU time used to create the geometry for each class. An analysis of this capability is included in appendix C. 8.3 GeomBuffer The Primitive-derived classes internally make use of the GeomBufferhelper class. This class allows geometry to be defined using an API similar to OpenGL s stateful display list geometry definition API. This capability is discussed in more detail in appendix C and may be useful for porting OpenGL programs. 8.4 Rasters java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.NodeComponent | +–javax.media.j3d.Geometry | +–javax.media.j3d.Raster The Rasterclass serves double duty in Java 3D. It can be used to either render an image into the 3D scene at a given location or to read the depth components of the 3D scene. The first application is much more common and easier to describe because it truly represents geometry definition. 8.4.1 Rendering an image using a Raster A Rasterobject can be used to simply paste a 2Dimage into the 3D view. The Rasterhas a 3D location associated with it, and this serves as the upper-left corner of the rendered image. Note however that the image for the Rasteris rendered as-is and will not have any scaling, translation, or rotation applied to it regardless of the Raster s position within the scenegraph. A Rastermight be appropriate for graphical coordinate axis labels, for example. Since Rasteris derived from Geometryit must be encapsulated by a Shape3D Nodebefore it can be added to the scenegraph. There are six basic steps to using a Raster: 1. Create the BufferedImage. 2. Read in or generate the image data. 3. Create the ImageComponent2Dto wrap the BufferedImage. 4. Create the Rasterto wrap the ImageComponent2D. 5. Create the Shape3Dto contain the Raster. 6. Add the Shape3Dto the scenegraph. For example: //create the image to be rendered using a Raster BufferedImage bufferedImage = new BufferedImage( 128, 128, BufferedImage.TYPE_INT_RGB); 116
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The Sphere Primitive (low resolution) Figure 8.7 The Sphere Primitive (high resolution) Figure 8.8 Sphere Primitive with an applied texture image of the Earth 8.2.5 Primitive flags All of the Primitiveshave a primitive flags (primflags) argument in one of their constructors. Primitive flags influence the attributes applied to the Shape3Dgeometry when it is generated internally for the Primitive. The available primitive flags are shown in table 8.1. Table 8.1 Primitive flags for Primitive derived classes Primitive flag Effect ENABLE_APPEARANCE_MODIFY Set ALLOW_APPEARANCE_READ and ALLOW_APPEARANCE_WRITE capabilities on the generated geometry’s Shape3D nodes. ENABLE_GEOMETRY_PICKING Set ALLOW_INTERSECT capability on the generated geometry. GENERATE_NORMALS Generate normal vectors along with geometry. GENERATE_NORMALS_INWARD Normal vectors flipped along the surface. GENERATE_TEXTURE_COORDS Generate texture coordinates along with geometry. GEOMETRY_NOT_SHARED Generate geometry that will not be shared by another scene graph node. After a Primitivehas been generated, the capabilities for the Shape3Dsubparts can also be accessed by calling getShape(partid).setCapability(ALLOW_INTERSECT); Note that the setPrimitiveFlagsmethod should not be used, as it does not have any effect once the Primitivehas been created. Unless primitive flags are explicitly supplied, the default GENERATE_NORMALSprimitive flag is used. In other words, both vertex coordinates and normal vectors are generated (to allow surfaces to be lighted). 115
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Figure 8.5 The Cylinder Primitive int BODY = 0; int TOP = 1; int BOTTOM = 2; The default number of surfaces created for the body is 15along the X-axis and 1along the Y-axis, the disks are created as 15-sided polygons. Again, use the most complex form of the constructor to vary the number of surfaces generated for the cylinder: public Cylinder(float radius, float height, int primflags, int xdivision, int ydivision, Appearance ap) { 8.2.4 Sphere java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.Node | +–javax.media.j3d.Group | +–com.sun.j3d.utils.geometry.Primitive | +–com.sun.j3d.utils.geometry.Sphere The Sphere Primitivedefines a sphere with 15 divisions in both the X- and Y-axes, illustrated in figures 8.6 through 8.8. Use the most customizable form of the constructor to vary the number of surfaces created for the Sphere: public Sphere(float radius, int primflags, int divisions, Appearance ap) Figure 8.6 114
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Figure 8.3 The Cone Primitive (low resolution) Figure 8.4 The Cone Primitive (high resolution) By default, 15 surfaces are generated for the sides of the Cone. This can be increased or decreased by using the most customizable constructor: public Cone(float radius, float height, int primflags, int xdivision, int ydivision, Appearance ap) The geometry for the Coneconsists of a Cylindertapering from the supplied radius at one end to zero radius at the other end. A disk is created using the same number of divisions as the Cylinderand aligned to close the open end of the Cylinder. 8.2.3 Cylinder java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.Node | +–javax.media.j3d.Group | +–com.sun.j3d.utils.geometry.Primitive | +–com.sun.j3d.utils.geometry.Cylinder The Cylinder Primitivedefines a capped cylinder, illustrated in figure 8.5. Cylinderis composed from three Shape3Dcomponents: Body, Topdisk, and Bottomdisk. 113
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//enable lighting and assign material m.setLightingEnable(true); ap.setMaterial(m); //render the Box as a wire frame PolygonAttributes polyAttrbutes = new PolygonAttributes(); polyAttrbutes.setPolygonMode( PolygonAttributes.POLYGON_LINE ); polyAttrbutes.setCullFace(PolygonAttributes.CULL_NONE); ap.setPolygonAttributes(polyAttrbutes); //create the box and assign the appearance Box BoxObj = new Box(1.5f, 1.5f, 0.8f, Box.GENERATE_NORMALS | Box.GENERATE_TEXTURE_COORDS, ap); //load and assign a texture image and set texture parameters TextureLoader tex = new TextureLoader(”texture.jpg”, “RGB”, this); if (tex != null) ap.setTexture(tex.getTexture()); TextureAttributes texAttr = new TextureAttributes(); texAttr.setTextureMode(TextureAttributes.MODULATE); ap.setTextureAttributes(texAttr); 8.2.2 Cone java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.Node | +–javax.media.j3d.Group | +–com.sun.j3d.utils.geometry.Primitive | +–com.sun.j3d.utils.geometry.Cone Conedefines a simple ConePrimitivewith a radius and a height, illustrated in figures 8.3 and 8.4. It is a capped cone centered at the origin with its central axis aligned along the Y-axis. The center of the Coneis defined to be the center of its bounding box (rather than its centroid). If the GENERATE_TEXTURE_COORDS flag is set, the texture coordinates are generated so that the texture gets mapped onto the Conesimilarly to a Cylinder, except without a top cap. Coneconsists of the following Shape3Dobjects: ALIGN=”JUSTIFY”>int BODY = 0; “JUSTIFY”>int CAP = 1; 112
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.To facilitate this relationship the Primitiveclass is derived from Group. The Java 3D scenegraph, however, can only have Leaf-derived geometric objects as leaf nodes, and many operations, such as picking for mouse-based selection, are performed on Shape3D-derived objects. This lack of compatibility between Shape3Dobjects and Primitiveobjects is something that Sun will address with future releases of Java 3D. Additionally, it is not generally possible to derive a class from Primitivebecause the class is not designed to be extensible. For example Primitive.java contains the following code: static final int SPHERE = 0×01; static final int CYLINDER = 0×02; static final int CONE = 0×04; static final int BOX = 0×08; This extremely non-object-oriented approach to differentiating between instances of objects derived from Primitiveessentially makes it impossible for application developers to safely create new Primitive-derived classes. In general, classes at the top of a class hierarchy should not have knowledge of derived classes. Example code for all of the Primitive-derived classes is defined in the Sun ConicWorld Java 3D demo directory. The ConicWorld demo creates a variety of Primitiveobjects with various lighting, material, and texture attributes. The following subsections describe the simple geometric Primitivesdefined in com.sun.j3d.utils.geometry. 8.2.1 Box java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.Node | +–javax.media.j3d.Group | +–com.sun.j3d.utils.geometry.Primitive | +–com.sun.j3d.utils.geometry.Box Box defines a simple six-sided cube, illustrated in figure 8.2. Unfortunately for Swing developers this name conflicts with the Swing class javax.swing.Boxso if your application uses Swing you should reference the Java 3D class explicitly, as in the following: com.sun.j3d.utils.geometry.Box box = new com.sun.j3d.utils.geometry.Box( 0.5f, 0.5f, 0.5f, null); 110
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Figure 8.2 The Box Primitive Box contains the following Shape3Dobjects: FRONT = 0; BACK = 1; RIGHT = 2; LEFT = 3; TOP = 4; BOTTOM = 5; The identifiers are used as indices into the PrimitiveGroup Node. In other words, to retrieve the FRONT face of the cube, you must call: Shape3D frontFace = box.getShape(Box.FRONT ); This is defined in Box.java as: public Shape3D getShape(int partId) { if (partId < FRONT || partId > BOTTOM) return null; return (Shape3D)((Group)getChild(0)).getChild(partId); } The faces of the Boxare Shape3Dobjects and are children of the first Nodeadded to the Group. The first Nodeof the Groupis a TransformGroupobject that allows the Boxto be moved as a whole. Thus, modifying the scale, rotation, and translation of the TransformGroup s Transform3Dapplies the scale, rotation, and translation to all of its child Nodesalso. The Sun example ConicWorld/BoxExample.java provides an example of creating Boxesand loading and applying texture images to Boxes. //Set Appearance attributes //first, create an appearance Appearance ap = new Appearance(); //create a colored material Color3f aColor = new Color3f(0.1f, 0.1f, 0.1f); Color3f eColor = new Color3f(0.0f, 0.0f, 0.0f); Color3f dColor = new Color3f(0.8f, 0.8f, 0.8f); Color3f sColor = new Color3f(1.0f, 1.0f, 1.0f); Material m = new Material(aColor, eColor, dColor, sColor, 80.0f); 111
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Figure 8.1 Geometric objects derived from Primitive: sphere, box, cylinder, and cone. Note the different resolution options and how the Primitives are triangulated when drawn as wire frames Primitive is not part of the Java 3D package (javax.media.j3d) but has been defined in the Java 3D utilities package (com.sun.java.j3d.utils). The Primitiveclass serves as the base class for several simple geometric shapes that can act as building blocks for Java 3D developers. The Java 3D Primitive-derived classes have been illustrated in figure 8.1. Primitiveis derived from Group that is, it is not a Shape3Dobject. This is important a Primitive is not a shape or geometric object, but is rather a collection of Shape3Dobjects. Primitiveprovides methods to access the subcomponents of the Group. There is therefore an important distinction between modifying the characteristics of the Primitive(Groupsettings) and modifying the properties of the child Shape3Dobjects (Shape3Dsettings such as Material, Appearance, etc.) Because of serious class design issues regarding the Primitivebase class, I cannot recommend that any of the Primitive-derived classes be used in a Java 3D application of any complexity. The fundamental issue is that the Primitiveclass defines a has-a relationship for its geometry. That is, a single Primitiveis defined such that it is a container for its geometric parts. For example, Boxhas six geometric parts: FRONT, BACK, LEFT, RIGHT TOP, and BOTTOM 109
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The Shape3Dclass is essential to defining viewable geometry in Java 3D. The Shape3Dclass packages the geometry information for a visual object along with the appearance information that governs how the geometry is rendered. The Appearanceclass is covered in chapter 9 and includes a variety of rendering attributes (material, line, surface attributes, etc.). In addition, each Shape3Dmaintains a Boundsobject for use in collision detection and intersection testing between PickRays (lines) and other Shape3Dobjects in the scene. As is customary, Shape3Densures access to internal variables and attributes is subject to the capability bits that have been set for the Shape3Dobject. An example class derived from Shape3Dis the ColorCubeclass. The source code for the ColorCube class is available in the com.sun.java.j3d.utils.geometrypackage where ColorCubeis defined. The basic principle is to define geometry using one of the Geometry-derived classes such as QuadArrayand then assign the geometry to the Shape3Dusing setGeometry(…). GeometryArray-derived classes can also store the normal vectors, colors, and texture coordinates for each vertex defined. 8.1.1 The user data field A useful feature, defined in Shape3D s SceneGraphObjectbase class, is that each Shape3Dhas a user data object associated with it. This allows an arbitrary Object-derived class to be attached to the Shape3D object using: public void setUserData(java.lang.Object userData); public java.lang.Object getUserData(); The user data object can then be queried in response to scenegraph operations, for example selecting with the mouse. A selection utility will typically return the Shape3Dobject that was selected and an application-specific data structure will need to be retrieved to apply the results of the selection operation this can be stored in the user data field of the Shape3Dobject. The user data field can also be used to remove a scenegraph object once it has been added a useful function. This technique is described in chapter 5. 8.2 Primitives java.lang.Object | +–javax.media.j3d.SceneGraphObject | +–javax.media.j3d.Node | +–javax.media.j3d.Group | +–com.sun.j3d.utils.geometry.Primitive 108
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