OpenGL Color and Lighting.ppt

CGGM Lab. Tan-Chi Ho 2001 OpenGL Color and Lighting Color Example Color Example #include GL/glut.h void GL_display() { glBegin(GL_TRIANGLES); glColor3f(1,1, 1); // 白 glVertex2f(0.0, 3.0); glColor3f(0, 0,1); // 藍 glVertex2f(6.0, 1.5); glColor3f(0,1,1); // 黃 glVertex2f(4.0, 0.0); glEnd(); } Lighting Example Lighting Example #include GL/glut.h void GL_display() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glutSolidSphere(1.0, 16, 16); glFlush(); } Lighting Example void init() { GLfloat mat_diffuse[4] = {1.0, 1.0, 1.0, 1.0}; GLfloat mat_specular[4] = { 1.0, 1.0, 1.0, 1.0 }; GLfloat mat_shininess[] = { 50.0 }; GLfloat light_position[4] = { 1.0, 1.0, 1.0, 0.0 }; glClearColor(0.0, 0.0, 0.0, 0.0); glShadeModel(GL_SMOOTH); glEnable(GL_DEPTH_TEST); // z buffer enable glEnable(GL_LIGHTING); // enable lighting // set light property glEnable(GL_LIGHT0); glLightfv(GL_LIGHT0, GL_POSITION, light_position); // set material property glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse); glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular); glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess); } Color Two Color modes: RGBA Color Index Choosing between RGBA and Color Index glutInitDisplayMode(); (GLUT) glutInitDisplayMode(GL_RGBA) (for RGBA) glutInitDisplayMode(GL_INDEX) (for color index) Color RGBA mode: Four components Red, Green, Blue, and Alpha. Each component is normalize to 0.0~1.0 glColor {34}{sifd}[v](TYPE colors); Ex. glColor3f(0.0, 0.0, 0.0); // black color glColor4f(0.0, 1.0, 0.0, 1.0); // green color Color Color Index mode: Use a color map (lookup table) to prepare for a paint-by-number scene. OpenGL does not provide any routing to load color map (it’s load by window system). glIndex{sidf…}(TYPE c); Color Clearing the Window Use glClearColor() or glClearIndex() to specify the clear color. Call glClear(GL_COLOR_BUFFER_BIT); if need to clear the color buffer. Specifying shading model glShadeModel(GLenum mode); The parameter is e