Open GL Animation

Presented By:Kiran Munir08-SE-59

• Animation is the rapid display of a sequence of images of 2-D or 3-D artwork or model positions in order to create an illusion of movement.

• "Animation" would be the technique of giving "soul" to objects and drawings

• For animation • We can explicitly force the display

callback to be invoked by issuing the command glutPostRedisplay().

• For automated simulation• We need a mechanism for the window to

be continually updated automatically. • Idle Callback (glutIdleFunc()) • Timer Callback (glutTimerFunc()).

• The Idle Callback specifies a function that is invoked whenever the system is not handling any other callbacks or events.

• Timer Callback specifies a function that is invoked after a specified time period.

A Simple Animation

• float X=0.0;• float deltaX=0.01;

Void draw(void){ glClear (GL_COLOR_BUFFER_BIT); glBegin (GL_LINES); glVertex3f (X, 0.25,0.0); glVertex3f (1.0-X, 0.75,0.0); glEnd ( ); glFlush ();

X+=deltaX;if(X>=1.0 || X<=0.0){

deltaX=-deltaX;}glutPostRedisplay(); }

• Single Buffer Rendering• Hardware Dependence• Inconsistent speed

A Smooth Animation

• Now to compile and execute we see a smooth animated line segment

• Double buffering is insignificant In this case, but is important in drawing complex scenes.

• No real solution• Make faster computers slow• Important for consistency

• Animation Delay• Select the minimal hardware

configuration• Set a time delay for animation

• Glut Timed Callback• GlutTimerFunc();

• glutTimerFunc(time,function,arg)• This causes function() to be called

after time milliseconds with arg as an argument to function()

void Timer(int unused){

glutPostRedisplay();glutTimerFunc(30,Timer,0);

}

• At the end of 30 milliseconds the function timer is called again and dispatches the redisplay and timer messages.

• To compile and execute the program we see a much smoother animation.

• Simultaneously running applications can slow down your animation.

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