Java LWJGL

Haven’t tested the library yet, just got the HelloWorld program working by using JDK18 instead of JDK19 in Eclispse.

With JDK19 getting a JNI Error possibly caused by Project Panama.

https://www.lwjgl.org/download‘

https://jdk.java.net/java-se-ri/18

https://github.com/LWJGL/lwjgl3-wiki/wiki

GitBook a project I didn’t know about, sounds cool

https://coffeebeancode.gitbook.io/lwjgl-game-design/tutorials/chapter-0-getting-started-with-lwjgl

Default OpenGL Experience in Java is Bad

Following code acts in unexpected ways, tracking down problems takes time, windows view and camera enabled easily factors into Throughput vs Negated Throughput

import org.lwjgl.*;
import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;
import org.lwjgl.system.*;
import org.lwjgl.util.meshoptimizer.MeshoptAllocate;

import java.nio.*;

import static org.lwjgl.glfw.Callbacks.*;
import static org.lwjgl.glfw.GLFW.*;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.system.MemoryStack.*;
import static org.lwjgl.system.MemoryUtil.*;

public class HelloWorld {

	// The window handle
	private long window;

	public void run() {
		System.out.println("Hello LWJGL " + Version.getVersion() + "!");

		init();
		loop();

		// Free the window callbacks and destroy the window
		glfwFreeCallbacks(window);
		glfwDestroyWindow(window);

		// Terminate GLFW and free the error callback
		glfwTerminate();
		glfwSetErrorCallback(null).free();
	}

	private void init() {
		// Setup an error callback. The default implementation
		// will print the error message in System.err.
		GLFWErrorCallback.createPrint(System.err).set();

		// Initialize GLFW. Most GLFW functions will not work before doing this.
		if ( !glfwInit() )
			throw new IllegalStateException("Unable to initialize GLFW");

		// Configure GLFW
		glfwDefaultWindowHints(); // optional, the current window hints are already the default
		glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); // the window will stay hidden after creation
		glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE); // the window will be resizable

		// Create the window
		window = glfwCreateWindow(300, 300, "Hello World!", NULL, NULL);
		if ( window == NULL )
			throw new RuntimeException("Failed to create the GLFW window");

		// Setup a key callback. It will be called every time a key is pressed, repeated or released.
		glfwSetKeyCallback(window, (window, key, scancode, action, mods) -> {
			if ( key == GLFW_KEY_ESCAPE && action == GLFW_RELEASE )
				glfwSetWindowShouldClose(window, true); // We will detect this in the rendering loop
		});

		// Get the thread stack and push a new frame
		try ( MemoryStack stack = stackPush() ) {
			IntBuffer pWidth = stack.mallocInt(1); // int*
			IntBuffer pHeight = stack.mallocInt(1); // int*

			// Get the window size passed to glfwCreateWindow
			glfwGetWindowSize(window, pWidth, pHeight);

			// Get the resolution of the primary monitor
			GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor());

			// Center the window
			glfwSetWindowPos(
				window,
				(vidmode.width() - pWidth.get(0)) / 2,
				(vidmode.height() - pHeight.get(0)) / 2
			);
		} // the stack frame is popped automatically

		// Make the OpenGL context current
		glfwMakeContextCurrent(window);
		// Enable v-sync
		glfwSwapInterval(1);

		// Make the window visible
		glfwShowWindow(window);
	}
	
	private void log(String message) {
		System.out.println(message);
	}

	private void loop() {
		// This line is critical for LWJGL's interoperation with GLFW's
		// OpenGL context, or any context that is managed externally.
		// LWJGL detects the context that is current in the current thread,
		// creates the GLCapabilities instance and makes the OpenGL
		// bindings available for use.
		GL.createCapabilities();

		// Set the clear color
		glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
		
		// Run the rendering loop until the user has attempted to close
		// the window or has pressed the ESCAPE key.
		while ( !glfwWindowShouldClose(window) ) {
			glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear the framebuffer
			
			glLoadIdentity();
			
			glBegin(GL_TRIANGLES);
			glColor3f(0, 0, 1.0f);
		    glVertex3f( 1.0f, 3.0f, 0.0f);              
		    glVertex3f( -1.0f,0.0f, 0.0f);             
		    glVertex3f( 2.0f,0.0f, 0.0f);			

			glColor3f(1.0f, 0.0f, 0.0f);
		    glVertex3f( 0.0f, 1.0f, 0.0f);              
		    glVertex3f(-1.0f,-1.0f, 0.0f);             
		    glVertex3f( 1.0f,-1.0f, 0.0f);            
			glEnd();
						
			glfwSwapBuffers(window); // swap the color buffers

			// Poll for window events. The key callback above will only be
			// invoked during this call.
			glfwPollEvents();
		}
	}

	public static void main(String[] args) {
		new HelloWorld().run();
	}

}