Java tutorial
/* * Copyright LWJGL. All rights reserved. * License terms: http://lwjgl.org/license.php */ package org.lwjgl.demo.opengl.geometry; import static org.lwjgl.demo.opengl.util.DemoUtils.createShader; import static org.lwjgl.glfw.GLFW.*; import static org.lwjgl.opengl.GL11.*; import static org.lwjgl.opengl.GL15.*; import static org.lwjgl.opengl.GL20.*; import static org.lwjgl.opengl.EXTGeometryShader4.*; import static org.lwjgl.system.MemoryUtil.NULL; import java.io.IOException; import java.nio.FloatBuffer; import java.nio.IntBuffer; import org.joml.Matrix4f; import org.lwjgl.BufferUtils; import org.lwjgl.glfw.GLFWErrorCallback; import org.lwjgl.glfw.GLFWFramebufferSizeCallback; import org.lwjgl.glfw.GLFWKeyCallback; import org.lwjgl.glfw.GLFWVidMode; import org.lwjgl.opengl.GL; import org.lwjgl.opengl.GLCapabilities; import org.lwjgl.opengl.GLUtil; import org.lwjgl.system.Callback; /** * Demo how to render the silhouette/outline of a mesh using the geometry shader. * <p> * First, the triangles with adjacency information (GL_TRIANGLES_ADJACENCY) are calculated based on a normal * GL_TRIANGLES mesh. Using this, the geometry shader is invoked which checks whether each one of the three edges is a * silhouette edge by determining the dot product between the front face and the back/adjacent face. * * @author Kai Burjack */ public class SilhouetteDemo { long window; int width = 1024; int height = 768; int vao; int program; int viewProjMatrixUniform; Matrix4f viewProjMatrix = new Matrix4f(); FloatBuffer matrixBuffer = BufferUtils.createFloatBuffer(16); GLCapabilities caps; GLFWErrorCallback errCallback; GLFWKeyCallback keyCallback; GLFWFramebufferSizeCallback fbCallback; Callback debugProc; void init() throws IOException { glfwSetErrorCallback(errCallback = new GLFWErrorCallback() { GLFWErrorCallback delegate = GLFWErrorCallback.createPrint(System.err); @Override public void invoke(int error, long description) { if (error == GLFW_VERSION_UNAVAILABLE) System.err.println("This demo requires OpenGL 2.0 or higher."); delegate.invoke(error, description); } @Override public void free() { delegate.free(); } }); if (!glfwInit()) throw new IllegalStateException("Unable to initialize GLFW"); glfwDefaultWindowHints(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0); glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE); window = glfwCreateWindow(width, height, "Silhouette rendering with geometry shader", NULL, NULL); if (window == NULL) { throw new AssertionError("Failed to create the GLFW window"); } glfwSetFramebufferSizeCallback(window, fbCallback = new GLFWFramebufferSizeCallback() { @Override public void invoke(long window, int width, int height) { if (width > 0 && height > 0 && (SilhouetteDemo.this.width != width || SilhouetteDemo.this.height != height)) { SilhouetteDemo.this.width = width; SilhouetteDemo.this.height = height; } } }); glfwSetKeyCallback(window, keyCallback = new GLFWKeyCallback() { @Override public void invoke(long window, int key, int scancode, int action, int mods) { if (action != GLFW_RELEASE) return; if (key == GLFW_KEY_ESCAPE) { glfwSetWindowShouldClose(window, true); } } }); GLFWVidMode vidmode = glfwGetVideoMode(glfwGetPrimaryMonitor()); glfwSetWindowPos(window, (vidmode.width() - width) / 2, (vidmode.height() - height) / 2); glfwMakeContextCurrent(window); glfwSwapInterval(0); glfwShowWindow(window); caps = GL.createCapabilities(); if (!caps.GL_EXT_geometry_shader4) { throw new AssertionError("This demo requires the EXT_geometry_shader4 extension"); } debugProc = GLUtil.setupDebugMessageCallback(); glClearColor(0.55f, 0.75f, 0.95f, 1.0f); glEnable(GL_DEPTH_TEST); /* Create all needed GL resources */ createBoxVao(); createRasterProgram(); initProgram(); } static void createBoxVao() { FloatBuffer pb = BufferUtils.createFloatBuffer(3 * 8); pb.put(-1).put(-1).put(-1); // 0 pb.put(1).put(-1).put(-1); // 1 pb.put(-1).put(1).put(-1); // 2 pb.put(-1).put(-1).put(1); // 3 pb.put(1).put(1).put(-1); // 4 pb.put(-1).put(1).put(1); // 5 pb.put(1).put(-1).put(1); // 6 pb.put(1).put(1).put(1); // 7 pb.flip(); IntBuffer ib = BufferUtils.createIntBuffer(3 * 2 * 6); ib.put(0).put(3).put(5).put(5).put(2).put(0); // -X ib.put(6).put(1).put(4).put(4).put(7).put(6); // +X ib.put(3).put(0).put(1).put(1).put(6).put(3); // -Y ib.put(5).put(7).put(4).put(4).put(2).put(5); // +Y ib.put(1).put(0).put(2).put(2).put(4).put(1); // -Z ib.put(3).put(6).put(7).put(7).put(5).put(3); // +Z ib.flip(); // Create GL_TRIANGLES_ADJACENCY index buffer IntBuffer adj = BufferUtils.createIntBuffer(ib.remaining() * 2); Adjacency.computeAdjacency(ib, adj); // setup vertex positions buffer int vbo = glGenBuffers(); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, pb, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, 0L); // setup index buffer with adjacency indices int ibo = glGenBuffers(); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, adj, GL_STATIC_DRAW); } void createRasterProgram() throws IOException { int program = glCreateProgram(); int vshader = createShader("org/lwjgl/demo/opengl/geometry/silhouette-vs.glsl", GL_VERTEX_SHADER); int fshader = createShader("org/lwjgl/demo/opengl/geometry/silhouette-fs.glsl", GL_FRAGMENT_SHADER); int gshader = createShader("org/lwjgl/demo/opengl/geometry/silhouette-gs.glsl", GL_GEOMETRY_SHADER_EXT); glAttachShader(program, vshader); glAttachShader(program, fshader); glAttachShader(program, gshader); glBindAttribLocation(program, 0, "position"); glProgramParameteriEXT(program, GL_GEOMETRY_VERTICES_OUT_EXT, 6); glProgramParameteriEXT(program, GL_GEOMETRY_INPUT_TYPE_EXT, GL_TRIANGLES_ADJACENCY_EXT); glProgramParameteriEXT(program, GL_GEOMETRY_OUTPUT_TYPE_EXT, GL_LINE_STRIP); glLinkProgram(program); int linked = glGetProgrami(program, GL_LINK_STATUS); String programLog = glGetProgramInfoLog(program); if (programLog.trim().length() > 0) { System.err.println(programLog); } if (linked == 0) { throw new AssertionError("Could not link program"); } this.program = program; } /** * Initialize the shader program. */ void initProgram() { glUseProgram(this.program); viewProjMatrixUniform = glGetUniformLocation(this.program, "viewProjMatrix"); glUseProgram(0); } float angle = 0.0f; long lastTime = System.nanoTime(); void update() { long thisTime = System.nanoTime(); float diff = (thisTime - lastTime) / 1E9f; lastTime = thisTime; angle += diff; viewProjMatrix.setPerspective((float) Math.toRadians(30), (float) width / height, 0.01f, 50.0f) .lookAt(0.0f, 2.0f, 7.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f).rotateY(angle); } void render() { glUseProgram(this.program); glUniformMatrix4fv(viewProjMatrixUniform, false, viewProjMatrix.get(matrixBuffer)); glDrawElements(GL_TRIANGLES_ADJACENCY_EXT, 6 * 2 * 6, GL_UNSIGNED_INT, 0L); glUseProgram(0); } void loop() { while (!glfwWindowShouldClose(window)) { glfwPollEvents(); glViewport(0, 0, width, height); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); update(); render(); glfwSwapBuffers(window); } } void run() { try { init(); loop(); if (debugProc != null) debugProc.free(); errCallback.free(); keyCallback.free(); fbCallback.free(); glfwDestroyWindow(window); } catch (Throwable t) { t.printStackTrace(); } finally { glfwTerminate(); } } public static void main(String[] args) { new SilhouetteDemo().run(); } }