Oval collision detection not working properly

Question

So I\'m trying to implement a test where a oval can connect with a circle, but it\'s not working.

edist = (float) Math.sqrt(
    Math.pow((px + ((pwidth/2) )) -          


        

Answer 1

If you can find your foci you can check for collision with the pseudo code below. WARNING this only works for two ellipse collisions (ellipse and circle collisions work also).

r = length of semi major axis
a_x = x coordinate of foci 1 of the first ellipse
a_y = y coordinate of foci 1 of the first ellipse
b_x = x coordinate of foci 2 of the first ellipse
b_y = y coordinate of foci 2 of the first ellipse

c_x = x coordinate of foci 1 of the second ellipse
c_y = y coordinate of foci 1 of the second ellipse
d_x = x coordinate of foci 2 of the second ellipse
d_y = y coordinate of foci 2 of the second ellipse

p_x = (a_x+b_x+c_x+d_x)/4 // i.e. the average of the foci x values
p_y = (a_y+b_y+c_y+d_y)/4 // i.e. the average of the foci y values

if r >= ( sqrt( (p_x + a_x)^2+(p_y + a_y)^2 ) + sqrt( (p_x + a_x)^2+(p_y + a_y)^2 ) )
then collision

If you really want the derivation of this let me know and I'll provide it. But it uses the idea that the sum of the distances between the foci of an ellipse and any point on the edge of an ellipse are a set distance apart (the semi major axis). And solves for a point that is on the edge of both ellipsoids and if one exist then their is a collision.