plane_functions.h

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#pragma once
 
#include <liboscar/maths/aabb.h>
#include <liboscar/maths/aabb_functions.h>
#include <liboscar/maths/analytic_plane.h>
#include <liboscar/maths/common_functions.h>
#include <liboscar/maths/geometric_functions.h>
#include <liboscar/maths/plane.h>
#include <liboscar/maths/vector.h>
 
namespace osc
{
    // returns an `AnalyticPlane` converted from a point on a plane's surface, plus the plane's normal direction
    constexpr AnalyticPlane to_analytic_plane(const Vector3& point, const Vector3& normal)
    {
        return AnalyticPlane{.distance = dot(point, normal), .normal = normal };
    }
 
    // returns an `AnalyticPlane` converted from a (point-normal form) `Plane`
    constexpr AnalyticPlane to_analytic_plane(const Plane& plane)
    {
        return AnalyticPlane{.distance = dot(plane.origin, plane.normal), .normal = plane.normal};
    }
 
    // returns the signed distance between the (normal-oriented) surface of `plane` and `vector`
    constexpr float signed_distance_between(const AnalyticPlane& plane, const Vector3& vector)
    {
        return dot(vector, plane.normal) - plane.distance;
    }
 
    // returns the signed distance between the (normal-oriented) surface of `plane` and `vector`
    constexpr float signed_distance_between(const Plane& plane, const Vector3& vector)
    {
        return dot(vector, plane.normal) - dot(plane.origin, plane.normal);
    }
 
    // tests if `aabb` is entirely in front of `plane`
    inline bool is_in_front_of(const AnalyticPlane& plane, const AABB& aabb)
    {
        // originally found in: https://learnopengl.com/Guest-Articles/2021/Scene/Frustum-Culling
        // which was based on : https://gdbooks.gitbooks.io/3dcollisions/content/Chapter2/static_aabb_plane.html
        const float r = dot(half_widths_of(aabb), abs(plane.normal));
        return signed_distance_between(plane, centroid_of(aabb)) > r;
    }
 
    // tests if `aabb` is entirely in front of `plane`
    inline bool is_in_front_of(const Plane& plane, const AABB& aabb)
    {
        return is_in_front_of(to_analytic_plane(plane), aabb);
    }
}