## Plane-to-plane

Two planes intersecting results in an infinite line between the two planes:

We don't actually care about this line. We just want a true or false Boolean to know if the planes intersect. Two planes intersect if they are not parallel. If the **normals** of the plane point in different directions, the planes intersect. If the normals of the plane point in the same direction, they do not intersect.

### Getting ready

We are going to implement a function to test if two planes intersect. This function will only return a Boolean result, not the line of intersection.

### How to do it…

Follow the given steps to determine if two planes are intersecting:

Declare the

`PlanePlane`

function in`Geometry3D.h`

:bool PlanePlane(const Plane& plane1, const Plane& plane2);

Implement the

`PlanePlane`

function in`Geometry3D.cpp`

:bool PlanePlane(const Plane& plane1, const Plane& plane2) {

Compute the direction of the intersection line

// Cross product returns 0 when used on parallel lines vec3 d = Cross(plane1...