OpenGL overview (đồ họa máy TÍNH SLIDE)

OpenGL Overview OpenGL and GLUT Overview • What is OpenGL & what can it for me? • OpenGL in windowing systems • Why GLUT • A GLUT program template What Is OpenGL? • Graphics rendering API – – • a cross-platform API high-quality color images composed of geometric and image primitives widely used in CAD, virtual reality, scientific visualization, information visualization and video game development OpenGL Architecture OpenGL as a Renderer • Geometric primitives – • points, lines and polygons Image Primitives – – images and bitmaps separate pipeline for images and geometry • • linked through texture mapping Rendering depends on state – colors, materials, light sources, etc Related APIs • • • AGL, GLX, WGL – glue between OpenGL and windowing systems GLU (OpenGL Utility Library) – – part of OpenGL NURBS, tessellators, quadric shapes, etc GLUT (OpenGL Utility Toolkit) – – – – portable windowing API keyboard and mouse input Geometric primitives: cubes, spheres, and teapot not officially part of OpenGL OpenGL and Related APIs application program OpenGL Motif GLUT widget or similar GLX, AGL or WGL X, Win32, Mac O/S software and/or hardware GLU GL What is JOGL? • Java OpenGL is a wrapper library by the Game Technology Group at Sun Microsystems that allow OpenGL to be used in Java • • • The base OpenGL C API is accessed in JOGL via Java Native Interface (JNI) calls The straightforward mapping of the OpenGL C API to Java methods Other Java OpenGL wrappers: GL4Java, JGL, LWJGL (Light-Weight Java Game Library) Setting Up JOGL 2.0x • Download the latest "stable" release from JogAMP http://jogamp.org/deployment/jogamp-current/archive Select "jogamp-all-platforms.7z" • Setup Library – – Copy the necessary jar-file, native libraries of your operating platform, and source-files into the appropriate sub-directories for Win32, copy • • • • "jar\gluegen-rt.jar", "jar\jogl.all.jar" into "jar"; all files in "lib\windows-i586" into "lib"; "gluegen-java-src.zip", "jogl-java-src.zip" into "src" Unzip the javadocs downloaded into "javadoc" Preliminaries • Headers Files // must import OpenGL im p ort javax.media.opengl.GL2; // import GL constants im p ort static javax.media.opengl.GL2.*; im p ort javax.media.opengl.glu.GLU; im p ort com.jogamp.opengl.util.gl2.GLUT im p ort javax.media.opengl.GLAutoDrawable; im p ort javax.media.opengl.GLCapabilities; im p ort javax.media.opengl.GLEventListener; im p ort javax.media.opengl.GLProfile; im p ort javax.media.opengl.awt.GLJPanel; Shapes Tutorial Controlling Rendering Appearance • From Wireframe to Texture Mapped OpenGL’s State Machine • All rendering attributes are encapsulated in the OpenGL State – – – – rendering styles shading lighting texture mapping Manipulating OpenGL State • Appearance is controlled by current state for each (primitive to render) { update OpenGL state render primitive } • Manipulating vertex attributes is most common way to manipulate state • • • glColor*() / glIndex*() glNormal*() glTexCoord*() Controlling current state • Setting State – – – • glPointSize(size); glLineStipple(repeat, pattern); glShadeModel(GL_SMOOTH); Enabling Features – – – glEnable(cap); glDisable(cap); cap is a feature like: • GL_LIGHTING, GL_TEXTURE_2D, GL_CULL_FACE, GL_BLEND, OpenGL State Variables • You can query the State Machine to determine the state of any variable • Any feature you enable or disable with glEnable / glDisable as well as numeric settings set with glSet can be queried with the many variations of glGet • Example byte color[3]; gl.glColor3ub(color[0], color[1], color[2]); gl.glColor3bv(color); fl o at colorf[3]; gl.glGetFloatv(GL_CURRENT_COLOR, colorf, 0); Animation and Depth Buffering Depth Buffering and Animation • Discuss double buffering and animation • Discuss hidden surface removal using the depth buffer Animation using Double Buffering 1 2 Front Buffer Back 16 16 Display Buffer Animation and Double Buffering • Request a double buffered color buffer – • Default for JOGL Clear color buffer – gl.glClear(GL_COLOR_BUFFER_BIT); • Render scene • Request swap of front and back buffers – • gl.glFlush(); Repeat steps - for animation Depth Buffering and Hidden Surface Removal 1 2 Color Buffer 16 Depth 16 Display Buffer Hidden Surface Removal Depth Buffering Using OpenGL • • • • • Request a depth buffer Enable depth buffering – glEnable(GL_DEPTH_TEST); Clear color and depth buffers – glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); Render scene Swap color buffers An Updated Program Template • Depth Buffer phải xóa trước vẽ p u b lic void display(G LAutoD raw able draw able) { G L2 gl= draw able.getG L().getG L2(); // clear color and depth buff ers gl.glClear(G L_CO LO R_BU FFER_BIT | G L_D EPTH _BU FFER_BIT); gl.glLoadIdentity(); gl.glTranslatef(0.0f,0.0f,-5.0f); } An Updated Program Template (cont) void init() { glClearColor(0.0, 0.0, 1.0, 1.0); } void drawScene() { fl o at vertices[] = { … }; fl o at colors[] = { … }; gl.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); gl.glBegin(GL_TRIANGLE_STRIP); /* calls to glColor*() and glVertex*() */ gl.glEnd(); gl.glflush(); } .. .OpenGL and GLUT Overview • What is OpenGL & what can it for me? • OpenGL in windowing systems • Why GLUT • A GLUT program template What Is OpenGL? • Graphics rendering... // must import OpenGL im p ort javax.media .opengl. GL2; // import GL constants im p ort static javax.media .opengl. GL2.*; im p ort javax.media .opengl. glu.GLU; im p ort com.jogamp .opengl. util.gl2.GLUT... javax.media .opengl. GLAutoDrawable; im p ort javax.media .opengl. GLCapabilities; im p ort javax.media .opengl. GLEventListener; im p ort javax.media .opengl. GLProfile; im p ort javax.media .opengl. awt.GLJPanel;