Like the topic says, the following code is based on top down grid style collision detection and movement… So I have this ball which is moving around tiles… let me just show you all the code first then I will mention the problem:-
if (isReady && isMovin)
{
//trace("speed is " + speed);
speedX = Math.cos(angle) * speed * flagX;
speedY = Math.sin(angle) * speed * flagY;
x_pos = this.x + speedX;
y_pos = this.y + speedY;
left = Math.floor((x_pos - 9) / tile_size);
bottom = Math.floor((y_pos + 9) / tile_size);
top = Math.floor((y_pos - 9) / tile_size);
right = Math.floor((x_pos + 9) / tile_size);
top_left = level[top][left];
bottom_left = level[bottom][left];
top_right = level[top][right];
bottom_right = level[bottom][right];
//no wall encountered carry on
if (top_left != 1 && bottom_left != 1 && top_right != 1 && bottom_right != 1)
{
this.x += speedX;
this.y += speedY;
}
else //code for checking collision with walls
{
if (top_left == 1 && bottom_left == 1 && speedX < 0)
{
this.x = (left + 1) * tile_size + 10;
//this.y += speedY;
speed -= 0.2;
flagX = -flagX;
}
else if (top_right == 1 && bottom_right == 1 && speedX > 0)
{
this.x = (right - 1) * tile_size + 8;
//this.y += speedY;
speed -= 0.2;
flagX = -flagX;
}
else
{
this.x += speedX;
}
if (top_right == 1 && top_left == 1 && speedY < 0)
{
this.y = (top + 1) * tile_size + 9;
//this.x += speedX;
speed -= 0.2;
flagY = -flagY;
}
else if (bottom_left == 1 && bottom_right == 1 && speedY > 0)
{
this.y = (bottom - 1) * tile_size + 10;
//this.x += speedX;
speed -= 0.2;
flagY = -flagY;
}
else
{
this.y += speedY;
}
}
speed -= fric;
if (speed <= 0)
isMovin = false;
}
As you all can see I am only testing the top(similar for bottom, right and left) collision only if both the variables are blocked like top_right and top_left both are equal to one then only I will change the direction.
The problem comes when only one of the variable is one (that is maybe top_right is 1 and top_left is not) then the ball goes straight or movement becomes jittery cause I havent added the code for checking with single variable. My issue is that for any given variable for eg if top_right is one then the ball can be colliding either on bottom of that tile or on the left hand side of that tile, I am not able to diagnose that properly…
Here is pic of that issue:-
So the ball can be moving in direction 1 and it hits left hand side of tile and direction 2 hits bottom of the tile… how to diagnose which direction it hits.
Any help will be appreciated.
