rayCubeOverlap Function

private function rayCubeOverlap(line, cube, pntIntersect) result(overlap)

Function computes intersection of ray with cube

The algorithm for lineCubeOverlap used in this function is taken from http://www.siggraph.org/education/materials/HyperGraph/raytrace/ rtinter3.htm http://gamedev.stackexchange.com/questions/18436/ most-efficient-aabb-vs-ray-collision-algorithms

Arguments

Type IntentOptional Attributes Name
type(tem_line_type), intent(in) :: line

line segment to check for interection
type(tem_cube_type), intent(in) :: cube

cube to check intersection of line
real(kind=rk), intent(out), optional :: pntIntersect(3)

intersection point if there is intersection

Return Value logical


Called by

proc~~raycubeoverlap~2~~CalledByGraph proc~raycubeoverlap~2 rayCubeOverlap proc~tem_linecubeoverlap~2 tem_lineCubeOverlap proc~tem_linecubeoverlap~2->proc~raycubeoverlap~2

Contents

Source Code

rayCubeOverlap

Source Code

  function rayCubeOverlap( line, cube, pntIntersect ) result(overlap)
    ! ---------------------------------------------------------------------------!
    !> line segment to check for interection
    type(tem_line_type), intent(in) :: line
    !> cube to check intersection of line
    type(tem_cube_type), intent(in) :: cube
    !> intersection point if there is intersection
    real(kind=rk), optional, intent(out) :: pntIntersect(3)
    logical :: overlap
    ! ---------------------------------------------------------------------------!
    integer :: i
    real(kind=rk) :: t_near, t_far
    real(kind=rk) :: T_1, T_2, tmp
    ! ---------------------------------------------------------------------------!

    !initialize near point and var point
    t_near = 0.0_rk
    t_far = huge(t_far)

    dirLoop: do i=1,3 !x,y,z
      if (line%vec(i) .feq. 0._rk) then
        !line parallel to planes in this direction.
        !Line exactly on the cube origin is considered as overlap
        if ( (line%origin(i) < cube%origin(i)) &
          &  .or. (line%origin(i) >= cube%endPnt(i)) ) then
          !parallel and outside cube : no intersection possible
          overlap = .false.
          return
        end if
      else
        !line not parallel to cube

        !1st intersection point on one side of the cube plane
        T_1 = (cube%origin(i) - line%origin(i)) / line%vec(i)

        !2nd intersection point on one side of the cube plane
        T_2 = (cube%endPnt(i) - line%origin(i)) / line%vec(i)

        if (T_1 > T_2) then
          ! we want T_1 to hold values for intersection with near plane
          tmp = T_2
          T_2 = T_1
          T_1 = tmp
        end if

        if (T_1 > t_near) t_near = T_1

        if (T_2 < t_far) t_far = T_2

        if ( (t_near > t_far) .or. (t_far < 0) ) then
          overlap = .false.
          return
        end if
      end if
    end do dirLoop

    !point of intersection
    if(present(pntIntersect)) then
      pntIntersect = line%origin + t_near * line%vec
    endif
    !If we made it here, there is an intesection
    overlap = .true.

  end function rayCubeOverlap