Calculating Angle Of Deflection

I'm attempting

D = 2W - P

P = balls path
W = walls angle
D = deflection


In my pong game I made many moons ago, I just negated one of the vectors depending on which side I hit.
// Collide with something on the left or right
x = -x;
// Collide with something on above or below
y = -y;

This gave a "perfect" bounce for walls at 90 degree increments. I say "perfect" because it doesn't take friction, spinning of the ball, energy loss to deformation or heat, etc.

For walls of 45 degrees, I think just swapping the vectors should work.
// Collide with a 45 degree wall
z = x; // temp for swap
x = y;
y = z;

Now for walls at any given angle. [s]Since angle of hit is = angle of rebound, you will need to find a 2D vector perpendicular to the 2D vector you have.[/s] I don't know.

Edit: I would ponder it for a bit, but it is time for me to get ready to shove tons of food down my throat. Happy Thanksgiving!

You need to know the angle the ball travels at, and the angle of the wall the ball hits (known as the normal) (this also depends on which side the wall is hit, by 180 degrees).

Once you have both angles, new angle can be calculated as: [s]360 - ball_angle - 2 * wall_normal[/s] (not correct, looking for the right formula)[s]
[/s]

http://wiki.answers....gle_of_the_wall


A = Known angle
B = Unknown Reflection
C = Surface
If C = 0 { A + B = 1.57079633 }
Else { (A - C) + (B - C) = 1.57079633 }

Does that sound correct ?

oh god.

To the OP. working with angles is infact a complication of the situation

Given the normal [N] of the surface (the unit vector point out of the surface at right angle (which given your post, you either already have, or at least have the direction of the wall at right angles to the normal; in which case the normal is (-ey,ex) where (ex,ey) is the unit vector for the direction of the wall)
And the vector [V] corresponding to the balls direction of motion (doesn't need to be unit)

the reflected vector is: V - 2N(N.V) where N.V is the dot product of N and V, if you don't know what the dot procut is, then N.V = Nx*Vx + Ny*Vy, so that you end up with the vector { Vx - 2*Nx*dot, Vy - 2*Ny*dot } <-- no trigonometric functions needed.