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calculate reflection

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Oleg

Posts: 1
Nickname: hsikur
Registered: Apr, 2003

calculate reflection

Posted: Apr 20, 2003 8:53 AM

Hi

I have a problem with calculating the reflection of a ray from the mirror. I can do it if I know the angle that I used to turn the mirror, but then if I have more than one mirror I have a problem to calculate the right angle.
So, I'm thinking to use coordinate transformation to calculate reflection.

Anybody can help?

/* code that I use now */
public void paint(Graphics g)
{
// initial mirror coordinates
double mirror[] = { 120.0, 80.0, 120.0, 160.0 };

// initial ray coordinates
double ray[] = { 20.0, 120.0, 120.0, 120.0 };

// angle to turn the mirror
double angle = Math.toRadians(30);

// placeholder for new mirror coordinates after transformation
double mirror_new[] = new double[4];

// placeholder for coordinates of reflected ray
double reflect[] = new double[4];

// set turn angle for the mirror
AffineTransform at = new AffineTransform();
at.setToRotation(angle, 120, 120);
at.transform(mirror,0,mirror_new,0,2);

// draw mirror after turn
g.drawLine((int)mirror_new[0],(int)mirror_new[1],
(int)mirror_new[2],(int)mirror_new[3]);

// draw ray
g.drawLine((int)ray[0],(int)ray[1], (int)ray[2],(int)ray[3]);

// calculate reflection
// ???????
at.setToRotation(angle * 2, 120, 120);
at.transform(ray,0,reflect,0,2);
// ??????

// draw reflection ray
g.drawLine((int)reflect[2],(int)reflect[3], (int)reflect[0], (int)reflect[1]);
}

Thanks,
hsikur

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