Changing Direction

[yonimal676]

How do I make the ball change its trajectory after hitting a wall or the floor?

[yonimal676]

1. Decide what kind of collision was there left/right wall or the floor?

2. Document the axis at which the ball hit a wall/floor (x, y).

3. Document the angle of hit and determine the new angle to go by.

4. Go by that angle, and take lose of speed into consideration.

[yonimal676]

1. Decide what kind of collision was there left/right wall or the floor?

Declare an byte(int) variable, which have the following attributes:

0 = no collision | when none of these are true ↓:

1 = right wall | if (x + width >= screenX)

2 = left wall | if (x <= 0)

3 = ground | if (y + height >= screenY - groundHeight)

[yonimal676]

2. When one of these happen ↑, I'll update colX/Y in the same function.

For example:

        if (x + width >= screenX) { // ball touches the right of the screen.
            colX = x;   colY = y; // <--
            return collision = 1;
        }

[yonimal676]

3. Document the angle of hit and determine the new angle to go by.

This part is a bit more complex so I'll visualize:

Because ∅1 != ∅2, I need to take the angle right before the collision.

I GOT IT:

for example:

if (x + width >= screenX)  // ball touches the right of the screen.

{

if (colX == 0 && colY == 0)

{

colX = x;

colY = y;

}

if (collision == 0)

return collision = 1;

//else

if (colAngle == 0)

colAngle = 90 - (float) (180/Math.PI * angle);

}

so when it collides with a wall/the floor, it'll save the (x,y) and angle to i (the radian, actually) to colX, colY, colAngle.

[yonimal676]

Now calculate the new angle:

right wall:

Because ∅ isn't colAngle, I'll change it to this:
colAngle = 90 - angle;

FAIL

second attempt:

[yonimal676]

3. Document the angle of hit and determine the new angle to go by.

1. At every run, save the previously shown (x, y) of the last drawing and updating as (prevX, prevY) and calculate this:

Then when it collides:

Calculate the angle between: ball.x, colX + colY, prevX + prevY - into colAngle.

Now into different cases:

left wall:

ball.colToPrevAdj = ball.prevX - ball.colX;

ball.colToPrevOpp = ball.colY - ball.prevY;

ball.colAngle = (float) (Math.atan(ball.colToPrevOpp / ball.colToPrevAdj));

ball.colAngle = (float) Math.atan2(ball.colX, ball.colY);

OR: ball.colAngle = (float) Math.atan2(ball.prevY, ball.prevX);

BEAWARE THE: ball.colAngle = (float) Math.atan2(ball.prevX, ball.prevY);

this probably occurs due to arctacn being miscalculated:

[yonimal676]

4. Go by that angle (colAngle), and take loss of speed into consideration.

BUG: when the ball hits the wall, it moves accordingly, but not from colX/Y

DESC: when the ball collides it immediately teleports to initial point:
SOL: find to where it tp's to, than fix it to the intended point.

SUCCESS IN COL 2: