Introduction to Computer GraphicsFarhana Bandukwala, PhDLecture 19: Putting it all togetherOpenGL: glutInit() to glFlush()main(){ glutInit(&argc, argv);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB |GLUT_DEPTH);glutInitWindowSize(800, 800);glutCreateWindow(“Sample");glutDisplayFunc(renderScene);glutMainLoop();}Step 1: Initializing buffers2 (800x800) color buffersfront back1 (800x800) depth bufferStep 2: General parameter initialization & Light propertiesinitState() { glClearColor(0.0f,0.0f,0.0f,1.0f);glShadeModel(GL_SMOOTH);glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);glEnable(GL_DEPTH_TEST);glEnable(GL_NORMALIZE);GLfloat light_diffuse[]={1.0,1.0,0.50,1.0};GLfloat light_specular[]={1.00,1.00,1.00,1.0};GLfloat light_model_ambient[]={.7,.7,.7,1.0};glLightfv(GL_LIGHT0,GL_DIFFUSE,light_diffuse);glLightfv(GL_LIGHT0,GL_SPECULAR,light_specular);glLightf(GL_LIGHT0,GL_LINEAR_ATTENUATION,0.5f);}lightStep 3: Define object(s) modelvoid drawCylinder1() {glBegin(GL_QUAD_STRIP);{for (int ii=0;ii<numPts;ii++){setMaterialProperties(&mat_shininess[ii], mat_specular[ii], mat_diffuse[ii], mat_ambient[ii] );glNormal3f(0.0f,(GLfloat)xvals[ii],(GLfloat)yvals[ii]);glVertex3f((GLfloat)0.f,(GLfloat)xvals[ii],(GLfloat)yvals[ii]);glVertex3f((GLfloat)0.5f,(GLfloat)xvals[ii],(GLfloat)yvals[ii]);}glNormal3f(0.0f,(GLfloat)xvals[0],(GLfloat)yvals[0]);glVertex3f((GLfloat)0.f,(GLfloat)xvals[0],(GLfloat)yvals[0]);glVertex3f((GLfloat)0.5f,(GLfloat)xvals[0],(GLfloat)yvals[0]);}glEnd();}drawSphere(){ … }World bounding boxStep 4: Place objects in worldvoid renderScene(void){glMatrixMode(GL_MODELVIEW);glLoadIdentity();glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();}10000100001000011000010000102001Model view matrixWorld bounding boxStep 5: Specify viewpointvoid renderScene(void){glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt( 0.0,2.0,-3,1.5,0,0,0,1,0);glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();}−10000100001000011000010000.8.600.6-.8 100000.83210.5547-000.5547 0.8321 000011ccTTModel view matrix−10000100001020011000010000.8.600.6-.8 100000.83210.5547-000.5547 0.8321 000011ccTTWorld frustumStep 6: Specify frustum and add light positionvoid renderScene(void){GLfloat light_position[]={ 1.0,4.0,0.0,1.0};glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(75.0, aspectRatio, -2.0,5.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt( 0.0,2.0,-3,1.5,0,0,0,1,0);glLightfv(GL_LIGHT0,GL_POSITION,light_position);glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();}0100000000000viewzviewzviewzProjection matrixWorld frustumStep 7: Normalize frustum void renderScene(void){GLfloat light_position[]={ 1.0,4.0,0.0,1.0};glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(75.0, aspectRatio, -2.0,5.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt( 0.0,2.0,-3,1.5,0,0,0,1,0);glLightfv(GL_LIGHT0,GL_POSITION,light_position);glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();}−−−−+−−+−−+−0100)(2000)()(2000)()(2minmaxmaxminminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxzzzzzzzzyyyyyyviewzxxxxxxviewzNormalized Projection matrixStep 8: Scale to viewport coords & Rasterizevoid renderScene(void){GLfloat light_position[]={ 1.0,4.0,0.0,1.0};glViewport(0,0,width,height);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(75.0, aspectRatio, -2.0,5.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt( 0.0,2.0,-3,1.5,0,0,0,1,0);glLightfv(GL_LIGHT0,GL_POSITION,light_position);glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();glFlush();}World frustumdepthfrontbackStep 9: glutSwapBuffers() Æ switch front and back buffersvoid renderScene(void){GLfloat light_position[]={ 1.0,4.0,0.0,1.0};glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(75.0, aspectRatio, -2.0,5.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt( 0.0,2.0,-3,1.5,0,0,0,1,0);glLightfv(GL_LIGHT0,GL_POSITION,light_position);glPushMatrix();drawCylinder1();glPopMatrix();glPushMatrix();glTranslatef(2.0,0,0);drawSphere();glPopMatrix();glFlush();glutSwapBuffers();}World
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