demo_surface.f90 Source File

!> This program demonstrates the usage of a NURBS surface object to create, and finalize a NURBS surface.
!> It sets up control points and weights, generates the surface, and exports the control points
!> and the surface to VTK files at various stages.

program example_nurbs_surface

    use forcad, only: rk, nurbs_surface

    implicit none
    type(nurbs_surface) :: nurbs             !! Declare a NURBS surface object
    real(rk), allocatable :: Xc(:,:), Wc(:)  !! Arrays for control points and weights

    !-----------------------------------------------------------------------------
    ! Setting up the NURBS surface
    !-----------------------------------------------------------------------------

    !> Define control points for the NURBS surface
    Xc = generate_Xc(10, 10, 1.5_rk)

    !> Define weights for the control points
    allocate(Wc(size(Xc,1)), source=1.0_rk)

    !> Set control points and weights for the NURBS surface object
    call nurbs%set([10,10],Xc,Wc)

    !> Deallocate local arrays
    deallocate(Xc, Wc)

    !-----------------------------------------------------------------------------
    ! Refinement
    !-----------------------------------------------------------------------------

    !> Elevate the degree of the NURBS surface in the first and second directions
    call nurbs%elevate_degree(1,3)
    call nurbs%elevate_degree(2,3)

    !> Insert knots into the NURBS surface in the first and second directions
    call nurbs%insert_knots(1,[0.5_rk], [1])
    call nurbs%insert_knots(2,[0.5_rk], [1])


    !> Export control points to a VTK file
    call nurbs%export_Xc('vtk/demo_surface_Xc.vtk')

    !-----------------------------------------------------------------------------
    ! Creating the NURBS surface
    !-----------------------------------------------------------------------------

    !> Generate the NURBS surface with a resolution of 30x30
    call nurbs%create(res1=30, res2=30)


    !> Export the generated surface to a VTK file
    call nurbs%export_Xg('vtk/demo_surface_Xg.vtk')

    !> Export the parameter space to a VTK file
    call nurbs%export_Xth_in_Xg('vtk/demo_surface_Xth_in_Xg.vtk')

    !-----------------------------------------------------------------------------
    ! Visualization using PyVista
    ! Note: PyVista is required for visualization. Install it using `pip install pyvista`
    !-----------------------------------------------------------------------------

    !> Show the control geometry, geometry and parameters using PyVista
    call nurbs%show('vtk/demo_surface_Xc.vtk', 'vtk/demo_surface_Xg.vtk', 'vtk/demo_surface_Xth_in_Xg.vtk')

    !-----------------------------------------------------------------------------
    ! Finalizing
    !-----------------------------------------------------------------------------

    !> Finalize the NURBS surface object
    call nurbs%finalize()

contains

    !-----------------------------------------------------------------------------
    pure function generate_Xc(num_rows, num_cols, peak_height) result(control_points)
        integer, intent(in) :: num_rows, num_cols
        real(rk), intent(in) :: peak_height
        real(rk), allocatable :: control_points(:,:)
        integer :: i, j
        real(rk) :: x_spacing, y_spacing, x_offset, y_offset
        x_spacing = 1.0_rk / real(num_cols - 1, rk)
        y_spacing = 1.0_rk / real(num_rows - 1, rk)
        x_offset = -0.5_rk
        y_offset = -0.5_rk
        allocate(control_points(num_rows * num_cols, 3))
        do i = 1, num_rows
            do j = 1, num_cols
                control_points((i - 1) * num_cols + j, 1) = x_offset + real(j - 1, rk) * x_spacing
                control_points((i - 1) * num_cols + j, 2) = y_offset + real(i - 1, rk) * y_spacing
                control_points((i - 1) * num_cols + j, 3) = &
                    peak_height * exp(-((control_points((i - 1) * num_cols + j, 1) ** 2) &
                    + (control_points((i - 1) * num_cols + j, 2) ** 2))) + 0.5_rk * peak_height * 0.2_rk
            end do
        end do
    end function
    !-----------------------------------------------------------------------------

end program example_nurbs_surface