make_polyhedron Subroutine

    subroutine make_polyhedron(self)
        class(Polyhedron), intent(inout) :: self
        type(c_ptr) :: group
        real(wp) :: rgba(4), sphere(4)
        real(wp), allocatable :: v(:,:), normals(:,:), colors(:,:), segments(:,:)
        integer, allocatable :: idx(:,:)
        integer :: i, k, m
        if (.not. c_associated(self%nodes%contents)) return
        group = vkf_switch_create()
        if (iand(self%mode, POLY_FACES) /= 0 .and. size(self%tri, 2) > 0) then
            rgba = self%face_color_
            if (allocated(self%vertex_colors_)) rgba = [1.0_wp, 1.0_wp, 1.0_wp, 1.0_wp]
            rgba(4) = rgba(4) * self%opacity_
            call vertices_sphere(self%v, sphere(1:3), sphere(4))
            if (.not. self%lit_) then
                if (allocated(self%vertex_colors_)) then
                    call add(group, surface_node(self%v, self%tri, rgba, colors=self%vertex_colors_))
                else
                    call add(group, surface_node(self%v, self%tri, rgba))
                end if
            else if (self%smooth_) then                          ! shared vertices, normals averaged
                normals = vertex_normals(self%v, self%tri)
                if (allocated(self%vertex_colors_)) then
                    call add(group, surface_node(self%v, self%tri, rgba, normals, self%vertex_colors_, self%two_sided_, &
                                                 sphere))
                else
                    call add(group, surface_node(self%v, self%tri, rgba, normals, two_sided=self%two_sided_, &
                                                 sphere=sphere))
                end if
            else                                                ! flat: each triangle its own vertices
                m = size(self%tri, 2)
                allocate(v(3, 3 * m), normals(3, 3 * m), idx(3, m))
                do k = 1, m
                    do i = 1, 3
                        v(:, 3 * (k - 1) + i) = self%v(:, self%tri(i, k))
                    end do
                    normals(:, 3 * k - 2) = unit_normal(v(:, 3 * k - 2), v(:, 3 * k - 1), v(:, 3 * k))
                    normals(:, 3 * k - 1) = normals(:, 3 * k - 2)
                    normals(:, 3 * k) = normals(:, 3 * k - 2)
                    idx(:, k) = [3 * k - 2, 3 * k - 1, 3 * k]
                end do
                if (allocated(self%vertex_colors_)) then
                    allocate(colors(4, 3 * m))
                    do k = 1, m
                        do i = 1, 3
                            colors(:, 3 * (k - 1) + i) = self%vertex_colors_(:, self%tri(i, k))
                        end do
                    end do
                    call add(group, surface_node(v, idx, rgba, normals, colors, self%two_sided_, sphere))
                else
                    call add(group, surface_node(v, idx, rgba, normals, two_sided=self%two_sided_, sphere=sphere))
                end if
            end if
        end if
        if (iand(self%mode, POLY_EDGES) /= 0 .and. size(self%edge, 2) > 0) then
            allocate(segments(3, 2 * size(self%edge, 2)))
            do k = 1, size(self%edge, 2)
                segments(:, 2 * k - 1) = self%v(:, self%edge(1, k))
                segments(:, 2 * k) = self%v(:, self%edge(2, k))
            end do
            call add(group, line_node(segments, self%line_color_, self%width_, .true.))
        end if
        if (iand(self%mode, POLY_VERTICES) /= 0 .and. size(self%v, 2) > 0) &
            call add(group, marker_node(self%v, self%point_color_, self%point_size_, MARKER_DISK, 0.0_wp, c_null_ptr))
        call self%nodes%replace(group)
    end subroutine make_polyhedron