ray_sphere Function

public function ray_sphere(origin, dir, center, radius, near, far) result(hit)

Where the ray (origin, unit dir) meets the sphere of center and radius: the distances along the ray of where it enters and leaves (near <= far; near < 0 if the origin is inside). False if it misses, or the sphere is behind.

Arguments

Type IntentOptional Attributes Name
real(kind=wp), intent(in) :: origin(3)

the ray (dir: a unit vector)
real(kind=wp), intent(in) :: dir(3)

the ray (dir: a unit vector)
real(kind=wp), intent(in) :: center(3)

the sphere's center
real(kind=wp), intent(in) :: radius

its radius (> 0)
real(kind=wp), intent(out) :: near

distances along the ray (huge() if missed)
real(kind=wp), intent(out) :: far

distances along the ray (huge() if missed)

Return Value logical


Called by

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Source Code

    logical function ray_sphere(origin, dir, center, radius, near, far) result(hit)
        real(wp), intent(in) :: origin(3), dir(3)           !! the ray (dir: a unit vector)
        real(wp), intent(in) :: center(3)                   !! the sphere's center
        real(wp), intent(in) :: radius                      !! its radius (> 0)
        real(wp), intent(out) :: near, far                  !! distances along the ray (huge() if missed)
        real(wp) :: o(3), b, c, disc
        hit = .false.
        near = huge(1.0_wp)
        far = huge(1.0_wp)
        if (radius <= 0.0_wp) return
        o = origin - center
        b = dot_product(o, dir)
        c = dot_product(o, o) - radius * radius
        disc = b * b - c
        if (disc < 0.0_wp) return
        if (-b + sqrt(disc) < 0.0_wp) return
        near = -b - sqrt(disc)
        far = -b + sqrt(disc)
        hit = .true.
    end function ray_sphere