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Hwk1- A Tutorial of OPENGL ver2.0

Hwk1- A Tutorial of OPENGL ver2.0. We will introduce…. Draw a window by OpenGL Draw one/many polygons by OpenGL Rotate/Translate Matrix Push/ PopMatrix. Homework1. Please draw a walking robot!. TAs will offer…. Ex1a:Rotate/Translate/Push/ PopMatrix Ex1b:draw polygon/Keyboard function.

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Hwk1- A Tutorial of OPENGL ver2.0

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  1. Hwk1-A Tutorial of OPENGLver2.0

  2. We will introduce… • Draw a window by OpenGL • Draw one/many polygons by OpenGL • Rotate/Translate Matrix • Push/PopMatrix

  3. Homework1 • Please draw a walking robot!

  4. TAs will offer… • Ex1a:Rotate/Translate/Push/PopMatrix • Ex1b:draw polygon/Keyboard function

  5. First open Ex1b… • A basic OpenGLmain functionlooks like: int main(intargc, char** argv){ glutInit(&argc, argv); glutInitWindowSize(800, 800); glutInitWindowPosition(0, 0); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); glutCreateWindow("Homework_1b"); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutSpecialFunc(specialkey); glutMainLoop(); return 0; }

  6. What is in the Main function? • Windows size/starting position/name. • Display mode(how many color channels? …etc) • Tell the system “which function” handle the operations glutInitWindowSize(800, 800); glutInitWindowPosition(0, 0); glutCreateWindow("Homework_1b"); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutSpecialFunc(specialkey);

  7. void glutInit(int *argcp, char **argv); • Initializing the GLUT library • Should be called before any other GLUT funcitons • http://www.opengl.org/resources/libraries/glut/spec3/node10.html • void glutInitDisplayMode(unsigned int mode); • Specify a display mode for windows created. • GLUT_RGB / GLUT_RGBA / GLUT_INDEX • GLUT_SINGLE / GLUT_DOUBLE • GLUT_DEPTH / GLUT_STENCIL / GLUT_ACCUM • http://www.opengl.org/resources/libraries/glut/spec3/node12.html

  8. What is Display? • void glutDisplayFunc(void (*func)(void)); • Automatically called when the windows needs redraw (focus on/in, …etc) • draw function handler • call glutPostRedisplay() if you need to redraw immediately • http://www.opengl.org/resources/libraries/glut/spec3/node46.html

  9. What is in the Display function? • The draw part looks: glPushMatrix(); glTranslatef(-400+movement[0][0], movement[0][1], movement[0][2]); glColor3f(0.0, 0.0, 1.0); glBegin(GL_QUADS); glVertex3f(-100.0, 200.0, 250.0); glVertex3f(-100.0, -200.0, 250.0); glVertex3f(100.0, -200.0, 250.0); glVertex3f(100.0, 200.0, 250.0); glEnd(); glPopMatrix();

  10. Indicate the color(R,G,B) • From glBegin() to glEnd(): • Indicate every points’ position/color(if need)/normal,…etc glColor3f(0.0, 0.0, 1.0); glBegin(GL_QUADS); glVertex3f(-100.0, 200.0, 250.0); glVertex3f(-100.0, -200.0, 250.0); glVertex3f(100.0, -200.0, 250.0); glVertex3f(100.0, 200.0, 250.0); glEnd();

  11. Next 1a…

  12. Adding • glutTimerFunc(TimerFunction); • glRotatef(45, 0.0,1.0,0.0); • glTranslatef(0,0,500); • drawCooridinate() is another function just draw the cooridinates

  13. Basic prior: • Everything in OpenGL is represented as a matrix operation. • glMatrixMode(): Decide which matrix is now operated. glTranslatef( 0, 0, -1 );

  14. glTranslate{fd}( TYPE x,TYPEy,TYPE z ); • Multiplies current matrix by a matrix that moves an object by x,y,z • http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/glfunc03_9a05.asp glTranslatef( 0, 0, -1 );

  15. glRotate{fd}( TYPR angle,TYPEx,TYPRy,TYPE z ); • Multiplies current matrix by a matrix that rotates an object in a counterclockwise direction about the ray from origin to (x,y,z) with angle as the degrees. • http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/glfunc03_21d1.asp glRotatef( 45.0, 0, 0, 1);

  16. void glPushMatrix(); • Push current matrix into matrix stack. • Void glPopMatrix(); • Pop matrix from matrix stack • These stack operations of matrix is very useful for constructing a hierarchical structure. • http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/glfunc03_246w.asp

  17. To more details • Step by step

  18. drawCooridinate(); glutSolidTeapot(100.0); //glRotatef(45, 0.0,1.0,0.0); //glTranslatef(0,0,500); //drawCooridinate(); // glutSolidTeapot(50.0); // glTranslatef(0,0,-1000); // glutSolidTeapot(50.0); Current Matrix

  19. drawCooridinate(); glutSolidTeapot(100.0); glRotatef(45, 0.0,1.0,0.0); glTranslatef(0,0,500); drawCooridinate(); // glutSolidTeapot(50.0); // glTranslatef(0,0,-1000); // glutSolidTeapot(50.0); Current Matrix

  20. drawCooridinate(); glutSolidTeapot(100.0); glRotatef(45, 0.0,1.0,0.0); glTranslatef(0,0,500); drawCooridinate(); glutSolidTeapot(50.0); // glTranslatef(0,0,-1000); // glutSolidTeapot(50.0); Current Matrix

  21. … … glTranslatef(0,0,-1000); glutSolidTeapot(50.0); Current Matrix

  22. Question • If I want to “back” to the initial matrix, I can… • 1.glTranslatef(0,0, 1000); • glTranslatef(0,0, -500); • glRotatef(-45, 0.0,1.0,0.0); • Work, but stupid! • 1a.glTranslatef(0,0,500); • glRotatef(-45,0.0,1.0,0.0); …. Not good Current Matrix

  23. 2. Adding push/popMatrix as follows: glPushMatrix(); drawCooridinate(); glutSolidTeapot(100.0); glRotatef(45, 0.0,1.0,0.0); glTranslatef(0,0,500); drawCooridinate(); glutSolidTeapot(50.0); glTranslatef(0,0,-1000); glutSolidTeapot(50.0); glPopMatrix();

  24. glPushMatrix(); glRotatef(theta,0.0,1.0,0.0); ….. glPopMatrix(); glTranslatef(0,200,0); GLUquadricObj *quadObj=gluNewQuadric(); gluQuadricDrawStyle(quadObj,GLU_SILHOUETTE); gluSphere(quadObj,50,20,20); glTranslatef(0,-400,0); gluQuadricDrawStyle(quadObj,GLU_FILL); glColor3f(1.0,0.0,0.0); glScalef(10.0,1.0,1.0); gluSphere(quadObj,50,20,20);

  25. Hw1b void keyboard(unsigned char key, int x, int y){ switch(key){ case '2': //type 2, move forward (axis Z) movement[selected][2]+=10.0; break; case '8': //type 8, move backward(axis Z) movement[selected][2]-=10.0; break; case '4': //type 4, move left(axis X) movement[selected][0]-=10.0; break; case '6': //type 6, move wight(axis X) movement[selected][0]+=10.0; …….. …….. case 27: exit(0); break; }

  26. Hwk1 Requirement • Please draw a robot which can walk! • At least , robot have body(sphere or cube or etc.) with 2 feet, each has more than 2 part. • Users can control each joints’ rotation. • The robot can walk (by user changing the rotation degree of joints) • The robot can walk around. • Bonus: Design a special movement with rotation / translate

  27. Reference • NeHe Productionshttp://nehe.gamedev.net/

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