OPENGL

OpenGL OpenGL resources: www.opengl.org The Red Book, www.glprogramming.com/red/ Manual pages, www.opengl.org/sdk/docs/man3/

OpenGL OpenGL core library OpenGL Utility (GLU) OpenGL Utility Toolkit (GLUT) Header files: #include <GL/gl.h> #include <GL/glu.h> #include <GL/glut.h>

#include <GL/glut.h> // (or others, depending on the system in use) void init (void) { glClearColor (1.0, 1.0, 1.0, 0.0); // Set display-window color to white. glMatrixMode (GL_PROJECTION); // Set projection parameters. gluOrtho2D (0.0, 200.0, 0.0, 150.0); } void lineSegment (void) { glClear (GL_COLOR_BUFFER_BIT); // Clear display window. glColor3f (0.0, 0.0, 1.0); // Set line segment color to blue. glBegin (GL_LINES); glVertex2i (180, 15); // Specify line-segment geometry. glVertex2i (10, 145); glEnd ( ); glFlush ( ); // Process all OpenGL routines as quickly as possible. void main (int argc, char** argv) { glutInit (&argc, argv); // Initialize GLUT. glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode. glutInitWindowPosition (50, 100); // Set top-left display-window position. glutInitWindowSize (400, 300); // Set display-window width and height. glutCreateWindow ("An Example OpenGL Program"); // Create display window. init ( ); // Execute initialization procedure. glutDisplayFunc (lineSegment); // Send graphics to display window. glutMainLoop ( ); // Display everything and wait. OpenGL

OpenGL Point Functions glVertex*( ); * : 2, 3, 4 i (integer) s (short) f (float) d (double) Ex: glBegin(GL_POINTS); glVertex2i(50, 100); glEnd(); Ex: int p1[ ]={50, 100}; glBegin(GL_POINTS); glVertex2iv(p1); glEnd();

OpenGL Line Functions GL_LINES GL_LINE_STRIP GL_LINE_LOOP Ex: glBegin(GL_LINES); glVertex2iv(p1); glVertex2iv(p2); glEnd();

OpenGL glBegin(GL_LINES); GL_LINES GL_LINE_STRIP glVertex2iv(p1); glVertex2iv(p2); glVertex2iv(p3); glVertex2iv(p4); glVertex2iv(p5); glEnd(); GL_LINE_LOOP p3 p3 p5 p1 p1 p2 p4 p2 p4 p3 p5 p1 p2 p4

OpenGL Ex: glBegin(GL_POINTS); GL_POINTS glVertex2iv(p1); glEnd(); glPointSize(size); size: 1,2,… Ex: glPointSize(2.0); // 2x2 pixels p3 p5 p1 p2 p4

OpenGL Polygon Functions glRect*(x1, y1, x2, y2); Ex: Ex: i (integer) s (short) f (float) d (double) v (vector) Ex: glRecti(200, 100, 50, 250); Ex: int v1[ ]={200, 100}; int v2[ ]={50, 250}; glRectiv(v1, v2); (50, 250) (200, 100)

OpenGL Ex: GL_POLYGON glBegin (GL_POLYGON); glVertex2iv(p1); glEnd(); p6 p5 p1 p4 p2 p3 GL_POLYGON

OpenGL Ex: GL_TRIANGLES glBegin (GL_TRIANGLES); glVertex2iv(p1); glEnd(); p6 p5 p1 p4 p2 p3 GL_TRIANGLES

OpenGL Ex: GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN glBegin (GL_TRIANGLES); glVertex2iv(p1); glVertex2iv(p2); glVertex2iv(p6); glVertex2iv(p3); glVertex2iv(p4); glVertex2iv(p5); glEnd(); p6 p5 p1 p4 p2 p3 GL_TRIANGLES p6 p6 p5 p5 p1 p4 p1 p4 p2 p3 p2 p3 GL_TRIANGLE_STRIP GL_TRIANGLE_FAN

OpenGL Ex: GL_QUADS GL_QUAD_STRIP glBegin (GL_QUADS); glVertex2iv(p1); glEnd(); p8 p1 p4 p5 p7 p6 p3 p2 GL_QUADS GL_QUAD_STRIP

OpenGL RGB colors Red Green Blue Color Black 1 Cyan Magenta Yellow Black 1 Cyan Magenta Yellow White

OpenGL Color Functions glClearColor(r, g, b, a); 0.0 ≤ r, g, b, a ≤ 1.0 specifies the color for color buffers glClear(GL_COLOR_BUFFER_BIT); applies the clear color to the color buffers Ex: glClearColor(1.0, 1.0, 1.0, 0.0); // White glColor(GL_COLOR_BUFFER_BIT);

OpenGL Color Functions glColor3f(r, g, b); 0.0 ≤ r, g, b ≤ 1.0 Ex: glColor3f(1.0, 0.0, 0.0); // Red glColor3ub(r, g, b); 0 ≤ r, g, b ≤ 255 glColor3ub(255, 0, 0); // Red

OpenGL Reshape Function glutReshapeFunc(func); Ex: glutReshapeFunc(my_reshape_func);

OpenGL – Transformations Matrix Operations glMatrixMode routine: Projection mode (GL_PROJECTION) Modelview mode (GL_MODELVIEW) Texture mode Color mode

OpenGL – Transformations Modelview Mode glMatrixMode(GL_MODELVIEW); designates 4x4 modelview matrix as the current matrix. glLoadIdentity(); assigns the identity matrix to the current matrix.

OpenGL – Transformations Translate glTranslatef (tx, ty, tz); Scale glScalef (sx, sy, sz); Rotate glRotatef (theta, vx, vy, vz);

OpenGL I Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue glRecti(0,0,80,40); glFlush ( ); Modelview Matrix I

OpenGL I I.T Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue glRecti(0,0,80,40); glFlush ( ); Modelview Matrix I glColor3f (1.0, 0.0, 0.0); // red glTranslatef(10.0, 10.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T

OpenGL I I.T I.T.S Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue glRecti(0,0,80,40); glFlush ( ); Modelview Matrix I glColor3f (1.0, 0.0, 0.0); // red glTranslatef(10.0, 10.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T glColor3f (1.0, 0.0, 0.0); // red glScalef(2.0, 2.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T.S

OpenGL I I.T I.T.S I.T.S.R Modelview Matrix glColor3f (0.0, 0.0, 1.0); // blue glRecti(0,0,80,40); glFlush ( ); Modelview Matrix I glColor3f (1.0, 0.0, 0.0); // red glTranslatef(10.0, 10.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T glColor3f (1.0, 0.0, 0.0); // red glScalef(2.0, 2.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T.S glColor3f (0.0, 1.0, 0.0); // green glRotatef(20.0, 0.0, 0.0, 1.0); glRecti(0,0,80,40); glFlush ( ); I.T.S.R

OpenGL – Transformations Matrix Stack glPushMatrix (); glPopMatrix ();

OpenGL I I.T I.T.S I.T.R Modelview Matrix Stack glColor3f (0.0, 0.0, 1.0); // blue glRecti(0,0,80,40); glFlush ( ); I glColor3f (1.0, 0.0, 0.0); // red glTranslatef(10.0, 10.0, 0.0); glRecti(0,0,80,40); glPushMatrix(); glFlush ( ); I.T I.T glColor3f (1.0, 0.0, 0.0); // red glScalef(2.0, 2.0, 0.0); glRecti(0,0,80,40); glFlush ( ); I.T.S I.T glColor3f (0.0, 1.0, 0.0); // green glPopMatrix(); glRotatef(20.0, 0.0, 0.0, 1.0); glRecti(0,0,80,40); glFlush ( ); I.T.R

OpenGL Ex: ROBOT transform robot glPushMatrix() transform head draw head glPopMatrix() transform body transform left_arm draw left_arm transform right_arm draw right_arm draw body Ex: ROBOT

OpenGL – 2D Viewing Clipping Window Viewport Function gluOrtho2D (xwmin, xwmax, ywmin, ywmax); float or double Viewport Function glViewport (xvmin, yvmin, vpWidth, vpHeight); integer Window (xwmax, ywmax) Viewport vpHeight vpWidth (xvmin, yvmin) (xwmin, ywmin)

OpenGL – 2D Viewing Create Display Window Display Window Mode glutInit (&argc, &argv) glutInitWindowPosition (xTopLeft, yTopLeft) glutInitWindowSize (width, height) windowID=glutCreateWindow (“title”) glutDestroyWindow (windowID) Display Window Mode glutInitDisplayMode (mode) Ex: glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);

OpenGL – 2D Viewing Display Functions glutDisplayFunction (dFunc) dFunc (callback function) describes what is to be displayed in the current window glutPostRedisplay () Indicates that the contents of the current display window should be renewed glutIdleFunc (iFunc) iFunc is executed when there are no other events for the system to process glutMainLoop ()

OpenGL – 3D Viewing Projection glMatrixMode (GL_PROJECTION) Orthogonal Projection gluOrtho (xwmin, xwmax, ywmin, ywmax, dnear, dfar) Perspective Projection gluPerspective (theta, aspect, dnear, dfar) theta: field-of-view angle (00 – 1800) aspect: aspect ratio of the clipping window (width/height) dnear, dfar: positions of the near and far planes (must have positive values) glFrustum (xwmin, xwmax, ywmin, ywmax, dnear, dfar) if xwmin = -xwmax and ywmin = -ywmax then symmetric view volume

OpenGL – 3D Viewing glMatrixMode (GL_MODELVIEW) gluLookAt (x0, y0, z0, xref, yref, zref, Vx, Vy, Vz) Designates the origin of the viewing reference frame as, the world coordinate position P0=(x0, y0, z0) the reference position Pref=(xref, yref, zref) and the viewup vector V=(Vx, Vy, Vz) double-precision, floating-point values xw yw zw xv yv zv V P0 N Pref

OpenGL – 3D Viewing gluLookAt (x0, y0, z0, xref, yref, zref, Vx, Vy, Vz) Default parameters are: P0=(0,0,0) Pref=(0,0,-1) V=(0,1,0) xw yw zw xv yv zv V P0 Pref

OpenGL float eye_x, eye_y, eye_z; void init (void) { glClearColor (1.0, 1.0, 1.0, 0.0); // Set display-window color to white. glMatrixMode (GL_PROJECTION); // Set projection parameters. glLoadIdentity(); gluPerspective(80.0, 1.0, 50.0, 500.0); // degree, aspect, near, far glMatrixMode (GL_MODELVIEW); eye_x = eye_y = eye_z = 60; gluLookAt(eye_x, eye_y, eye_z, 0,0,0, 0,1,0); // eye, look-at, view-up } void main (int argc, char** argv) { glutInit (&argc, argv); // Initialize GLUT. glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode. glutInitWindowPosition (50, 500); // Set top-left display-window position. glutInitWindowSize (400, 300); // Set display-window width and height. glutCreateWindow ("An Example OpenGL Program"); // Create display window. glViewport (0, 0, 400, 300); init ( ); // Execute initialization procedure. glutDisplayFunc (my_objects); // Send graphics to display window. glutReshapeFunc(reshape); glutKeyboardFunc(keybrd); glutMainLoop ( ); // Display everything and wait.

OpenGL Functions Cube glutSolidCube (size) glutWireCube (size) Cone glutSolidCone (base_radius, height, slices, stacks) glutWireCone (base_radius, height, slices, stacks) Sphere glutSolidSphere (radius, slices, stacks) glutWireSphere (radius, slices, stacks) Teapot glutSolidTeapot (size) glutWireTeapot (size) Torus glutSolidTorus (inner_radius, outer_radius, nsides, rings) glutWireTorus (inner_radius, outer_radius, nsides, rings)

OpenGL Functions Tetrahedron glutSolidTetrahedron () glutWireTetrahedron () 4 sided Octahedron glutSolidOctahedron () glutWireOctahedron () 8 sided Dodecahedron glutSolidDodecahedron () glutWireDodecahedron () 12 sided Icosahedron glutSolidIcosahedron () glutWireIcosahedron () 20 sided

OpenGL glPolygonMode(GL_FRONT_AND BACK, GL_LINE) glEnable (GL_FOG) displays both visible and hidden edges glEnable (GL_FOG) glFogi (GL_FOG_MODE, GL_LINEAR) generates fog effect. Uses depth cueing. glEnable (GL_CULL_FACE) glDisable (GL_CULL_FACE) glCullFace (mode) used for backface removal GL_BACK (default), GL_FRONT (if inside a building), GL_FRONT_AND_BACK

OpenGL glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH) initializes GLUT, requests a depth buffer and a frame buffer glClear (GL_DEPTH_BUFFER_BIT) initially depth buffer has the background color. It must be cleared every time before displaying a new frame. glEnable (GL_DEPTH_TEST) glDisable (GL_DEPTH_TEST) to activate depth buffer routines glClearDepth (maxDept) to set maxDepth to another value (0.0 – 1.0) glDepthRange (nearNormDept, farNormDept) to adjust normalization values (defaults: near- 0.0, far- 1.0)

Diffuse and Specular Lightings I = Idiff + Ispec = ka Ia + kd Il (N.L) + ks Il (N.H)ns

OpenGL GLfloat pos[ ] = {x, y, z, w} (x, y, z): position w: type 1.0 – local (positional light) 0.0 – distant (directional light) glLightfv(GL_LIGHT1, GL_POSITION, pos) GL_POSITION sets the light position and type glEnable (GL_LIGHT1) glDisable (GL_LIGHT1)

OpenGL GLfloat color[ ] = {r, g, b, a} (r, g, b): RGB color (I) a: alpha (used only if color blending routines are active) glLightfv(GL_LIGHT1, GL_AMBIENT, color) glLightfv(GL_LIGHT1, GL_DIFFUSE, color) glLightfv(GL_LIGHT1, GL_SPECULAR, color) GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR set the light color

OpenGL GLfloat dir[ ] = {x, y, z} 1.0 if light source is not spotlight fl,angatten = 0.0 if Vobj.Vlight=cos a < cos ql (Vobj . Vlight )al otherwise OpenGL GLfloat dir[ ] = {x, y, z} (x, y, z): direction vector Vlight default direction (0.0, 0.0, -1.0) glLightfv(GL_LIGHT2, GL_SPOT_DIRECTION, dir) glLightfv(GL_LIGHT2, GL_SPOT_CUTOFF, c) c: cut off angle θ (0o-90o) glLightfv(GL_LIGHT2, GL_SPOT_EXPONENT, e) e: exponent value for angular intensity attenuation (0-128) Vlight Vobj ql a

OpenGL GLfloat ka[ ] = {r, g, b, a} GLfloat kd[ ] = {r, g, b, a} GLfloat ks[ ] = {r, g, b, a} (r, g, b): RGB color (k) a: alpha glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, ka) glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, kd) glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, ks) glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS, s) s: specular reflection exponent (0-128) GLfloat emissioncolor[ ] = {r, g, b, a} glMaterialfv(GL_FRONT, GL_EMISSION, emissioncolor)

OpenGL glColor4f(R, G, B, A) glEnable (GL_BLEND) glDisable (GL_BLEND) A: alpha parameter 1.0 – transparent 0.0 - opaque glEnable (GL_BLEND) glDisable (GL_BLEND)