3D Programming in Java Part II Doing it in Java. Can I do OpenGL in Java? Can I do OpenGL in Java? GL4Java. GL4Java. OpenGL.

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1 3D Programming in Java Part II Doing it in Java Joe Geigel So Far OpenGL C API Supported by most Graphics Cards Inventor /VRML Scene Graph based Object oriented sort of. Can I do OpenGL in Java? Java wrappers for OpenGL: Mesa: jgl JOGL (Java Bindings for OpenGL) Can I do OpenGL in Java? Java app JNI OpenGL Graphics Card Thin wrapper (1-1 mapping) of OpenGL functions GLU and GL GLUT not needed. Canvas classes gl4java.awt.glanimcanvas gl4java.awt.glcanvas gl4java.swing.glanimjpanel gl4java.swing.gljpanel gl4java.swing.simplegljapplet1 Accessing OpenGL functions Each canvas has an object gl that implements the GLFunc interface which includes all gl functions Each canvas has an object glu that implements the GLUFunc interface which includes all glu functions 1

2 Each canvas has an object glj which is the GLContext. GLContext main mapping from java to native OpenGL implementation. All native libraries and GLFunc* and GLUFunc* implementations can/should be loaded right here! Simulating GLUT behaviour: preinit - initialisation before creating GLContext init - 1st initialisation docleanup - OGL cleanup prior to context deletion display - render one frame reshape - to reshape (window resize) ReInit - ReInitialisation after stop for setsuspended(false) Look at some code. Applet In December 1995, Sun announced that it was working on a 3D API for Java Scene Graph Based Thrills for VRML developers Java app JNI OpenGL Java app JNI DirectX Packages javax.media.j3d Core classes com.sun.j3d.utils Utility classes Not officially part of javax.vecmath Vector / Matrix classes Graphics Card Graphics Card 2

3 basics 1. Create a Canvas3D object 2. Create a VirtualUniverse object 3. Create a Locale object, attaching it to the VirtualUniverse object 4. Construct a view branch graph a. Create a View object b. Create a ViewPlatform object c. Create a PhysicalBody object d. Create a PhysicalEnvironment object e. Attach ViewPlatform, PhysicalBody, PhysicalEnvironment, and Canvas3D objects to View object 5. Construct content branch graph(s) 6. Compile branch graph(s) 7. Insert subgraphs into the Locale basics Why the complex view model? was designed to work in VR applications Head Mounted Displays Physical environment vs. Virtual Environment Full Physical Body model of head For stereo viewing Basics 1. Create a Canvas3D Object 2. Create a SimpleUniverse object which references the earlier Canvas3D object a. Customize the SimpleUniverse object 3. Construct content branch 4. Compile content branch graph 5. Insert content branch graph into the Locale of the SimpleUniverse 1. public class Helloa extends Applet { 2. public Helloa() { 3. setlayout(new BorderLayout()); 4. GraphicsConfiguration config = 5. SimpleUniverse.getPreferredConfiguration(); 6. Canvas3D canvas3d = new Canvas3D(config); 7. add("center", canvas3d); BranchGroup scene = createscenegraph(); 10. scene.compile(); // SimpleUniverse is a Convenience Utility class 13. SimpleUniverse simpleu = new SimpleUniverse(canvas3D); // This moves the ViewPlatform back a bit so the 16. // objects in the scene can be viewed. 17. simpleu.getviewingplatform().setnominalviewingtransform(); simpleu.addbranchgraph(scene); 20. } // end of Helloa (constructor) 1. public BranchGroup createscenegraph() { 2. // Create the root of the branch graph 3. BranchGroup objroot = new BranchGroup(); // Create a simple shape leaf node, add it the scene graph. 6. // ColorCube is a Convenience Utility class 7. objroot.addchild(new ColorCube(0.4)); return objroot; 10. } // end of createscenegraph method of Helloa 11. } // end of class Helloa 3

4 VRML vs. differs significantly from VRML in its support for: Instancing (DEF and USE) Backgrounds Behaviors Interpolators Clipping Collision detection has richer semantics for scoping lights, fog, backgrounds, and behaviors VRML vs. does not have built-in support for: Primitive geometry (box, cone, cylinder, sphere) Specialized geometry (elevation grid, extrusion) Prototypes Inlines Routes Navigation All of these can be implemented atop vs. (and others) Low level (direct connection to hardware) Faster More difficult to program More bells and whistles Easier to program Slower Demo vs. (and others) The word on the street Even in the Sun camps is out JOGL is in. VRML and Java Java applet VRML External Authoring Interface (EAI) Allows external software components (e.g. applets) to modify node field values. Allows for creation of new nodes on the fly Java Web component VRML Browser VRML EAI calls 4

5 VRML Example VRML Example 3D Model Generation Stage is built from geometric primitives using stage dimensions. Audience seating Placement of seats Determine location of each Seat Use the Seat PROTO to instantiate individual seats Provide each seat with a unique name based on Section/Row/SeatNo. VRML Example Seat Selection Seat Selection scripts communicates with VRML Applet via EAI. Set mycolor message sent to Seat nodes corresponding to selected seats VRML Example Viewpoint Selection New viewpoint node created on-the-fly for selected seats using EAI. Newly created viewpoint nodes are activated as specified by Viewpoint Selection Applet via EAI. Problems with VRML/Java link External Authoring Interface (EAI) is not part of the VRML97 Standard Spec. Browser writers can ignore parts or all of the EAI and still be VRML97 compliant To be fixed with X3D? VRML and Java The word on the street is out j3d, a java based viewer for X3D files is in 5

6 So what do I use? VRML/X3D is a content-centric approach to building 3D worlds The application (browser) is standardized; only the content is variable VRML is good when operations on the content are simple and well-known (walk around and draw) VRML is primarily for contentdevelopers With X3D and standard EAI, external control is on the way So what do I use? / et al. is a programcentric approach to building 3D worlds Neither the application nor the content is standardized; both are variable is good when operations on the content are complex and application-specific is primarily for applicationdevelopers vs. (and others) Low level (direct connection to hardware) Faster More difficult to program More bells and whistles Easier to program Slower Vital Links: JOGL VRML/X3D j3d Questions? 6