Question

how do i find the intersection of a line and a quad?​

Answer 1

Compute the plane equation of the square (assuming the four points are coplanar),

Do a ray / plane intersection, this gives you either nothing (ray parallel to the square and I ignore the case where the ray is embedded in the plane) or a point,

Answer 2

Compute the plane equation of the square (assuming the four points are coplanar),

Do a ray / plane intersection, this gives you either nothing (ray parallel to the square and I ignore the case where the ray is embedded in the plane) or a point,