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OpenGL Sample Code - A 3D Analog Clock

OpenGL Sample Code - A 3D Analog Clock. Luke Yulu Chen. How to Program a 3D Analog Clock. Get System Time Convert Time to Rotation Angle Draw Hands for Hour, Minute and Second Make Hands Rotate with Time. Get System Time. Commands time_t time ( time_t * timer );

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OpenGL Sample Code - A 3D Analog Clock

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  1. OpenGL Sample Code- A 3D Analog Clock Luke Yulu Chen

  2. How to Program a 3D Analog Clock • Get System Time • Convert Time to Rotation Angle • Draw Hands for Hour, Minute and Second • Make Hands Rotate with Time

  3. Get System Time • Commands • time_t time ( time_t *timer ); • The time function returns the number of seconds elapsed since midnight (00:00:00), January 1, 1970, GMT, according to the system clock. • struct tm *localtime ( time_t *timer ); • Converts a time value and corrects for the local time zone. • Returns a pointer to the structure result.

  4. Get System Time • Structure tm struct tm { int tm_sec; // seconds after the minute [0,59] int tm_min; // minutes after the hour [0,59] int tm_hour; // hours since midnight [0,23] int tm_mday; int tm_mon; int tm_year; int tm_wday; int tm_yday; int tm_isdst; }

  5. rot_sec = - (float)curtime->tm_sec * (360.0/60.0); second degree per second Convert Time to Rotation Angle • Rotation Angle for a Second Hand • What is the angle for a hour hand?

  6. Draw Hands for Hour, Minute and Second • Composed by Sphere, Cylinder, Disk and Cone

  7. Draw Hands for Hour, Minute and Second • Rotate around X-Axis with -90 • Z-Axis points out of screen • PushMatrix ( ); • Rotatef (-90.0, 0.0, 0.0, 1.0); • glBegin ( … ); • … • glEnd ( … ); • PopMatrix ( );

  8. Make Hands Rotate with Time

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