honeycomb_core/cmap/builder/
grid.rs

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use crate::prelude::{BuilderError, CMap2, DartIdType, Vector2, Vertex2};
use crate::{attributes::AttrStorageManager, geometry::CoordsFloat};

// --- grid descriptor

/// # Grid description used by the map builder
///
/// The user must specify two out of these three characteristics (third is deduced):
///
/// - `n_cells: [usize; 3]` -- The number of cells per axis
/// - `len_per_cell: [T; 3]` -- The dimensions of cells per axis
/// - `lens: [T; 3]` -- The total dimensions of the grid per axis
///
/// ## Generics
///
/// - `T: CoordsFloat` -- Generic FP type that will be used by the map's vertices.
#[derive(Default, Clone)]
pub struct GridDescriptor<T: CoordsFloat> {
    pub(crate) origin: Vertex2<T>,
    pub(crate) n_cells: Option<[usize; 3]>,
    pub(crate) len_per_cell: Option<[T; 3]>,
    pub(crate) lens: Option<[T; 3]>,
    pub(crate) split_quads: bool,
}

macro_rules! setters {
    ($fld: ident, $fldx: ident, $fldy: ident, $fldz: ident, $zero: expr, $fldty: ty) => {
        /// Set values for all dimensions
        #[must_use = "unused builder object"]
        pub fn $fld(mut self, $fld: [$fldty; 3]) -> Self {
            self.$fld = Some($fld);
            self
        }

        /// Set x-axis value
        #[must_use = "unused builder object"]
        pub fn $fldx(mut self, $fld: $fldty) -> Self {
            if let Some([ptr, _, _]) = &mut self.$fld {
                *ptr = $fld;
            } else {
                self.$fld = Some([$fld, $zero, $zero]);
            }
            self
        }

        /// Set y-axis value
        #[must_use = "unused builder object"]
        pub fn $fldy(mut self, $fld: $fldty) -> Self {
            if let Some([_, ptr, _]) = &mut self.$fld {
                *ptr = $fld;
            } else {
                self.$fld = Some([$zero, $fld, $zero]);
            }
            self
        }

        /// Set z-axis value
        #[must_use = "unused builder object"]
        pub fn $fldz(mut self, $fld: $fldty) -> Self {
            if let Some([_, _, ptr]) = &mut self.$fld {
                *ptr = $fld;
            } else {
                self.$fld = Some([$zero, $zero, $fld]);
            }
            self
        }
    };
}

impl<T: CoordsFloat> GridDescriptor<T> {
    // n_cells
    setters!(n_cells, n_cells_x, n_cells_y, n_cells_z, 0, usize);

    // len_per_cell
    setters!(
        len_per_cell,
        len_per_cell_x,
        len_per_cell_y,
        len_per_cell_z,
        T::zero(),
        T
    );

    // lens
    setters!(lens, lens_x, lens_y, lens_z, T::zero(), T);

    /// Set origin (most bottom-left vertex) of the grid
    #[must_use = "unused builder object"]
    pub fn origin(mut self, origin: Vertex2<T>) -> Self {
        self.origin = origin;
        self
    }

    /// Indicate whether to split quads of the grid
    #[must_use = "unused builder object"]
    pub fn split_quads(mut self, split: bool) -> Self {
        self.split_quads = split;
        self
    }
}

// --- parsing routine

macro_rules! check_parameters {
    ($id: ident, $msg: expr) => {
        if $id.is_sign_negative() | $id.is_zero() {
            return Err(BuilderError::InvalidGridParameters($msg));
        }
    };
}

impl<T: CoordsFloat> GridDescriptor<T> {
    /// Parse provided grid parameters to provide what's used to actually generate the grid.
    #[allow(clippy::type_complexity)]
    pub(crate) fn parse_2d(self) -> Result<(Vertex2<T>, [usize; 2], [T; 2]), BuilderError> {
        match (self.n_cells, self.len_per_cell, self.lens) {
            // from # cells and lengths per cell
            (Some([nx, ny, _]), Some([lpx, lpy, _]), lens) => {
                if lens.is_some() {
                    eprintln!("W: All three grid parameters were specified, total lengths will be ignored");
                }
                #[rustfmt::skip]
                check_parameters!(lpx, "length per x cell is null or negative");
                #[rustfmt::skip]
                check_parameters!(lpy, "length per y cell is null or negative");
                Ok((self.origin, [nx, ny], [lpx, lpy]))
            }
            // from # cells and total lengths
            (Some([nx, ny, _]), None, Some([lx, ly, _])) => {
                #[rustfmt::skip]
                check_parameters!(lx, "grid length along x is null or negative");
                #[rustfmt::skip]
                check_parameters!(ly, "grid length along y is null or negative");
                Ok((
                    self.origin,
                    [nx, ny],
                    [lx / T::from(nx).unwrap(), ly / T::from(ny).unwrap()],
                ))
            }
            // from lengths per cell and total lengths
            (None, Some([lpx, lpy, _]), Some([lx, ly, _])) => {
                #[rustfmt::skip]
                check_parameters!(lpx, "length per x cell is null or negative");
                #[rustfmt::skip]
                check_parameters!(lpy, "length per y cell is null or negative");
                #[rustfmt::skip]
                check_parameters!(lx, "grid length along x is null or negative");
                #[rustfmt::skip]
                check_parameters!(ly, "grid length along y is null or negative");
                Ok((
                    self.origin,
                    [
                        (lx / lpx).ceil().to_usize().unwrap(),
                        (ly / lpy).ceil().to_usize().unwrap(),
                    ],
                    [lpx, lpy],
                ))
            }
            (_, _, _) => Err(BuilderError::MissingGridParameters),
        }
    }
}

// --- building routines

/// Internal grid-building routine
#[allow(clippy::too_many_lines)]
pub fn build_2d_grid<T: CoordsFloat>(
    origin: Vertex2<T>,
    [n_square_x, n_square_y]: [usize; 2],
    [len_per_x, len_per_y]: [T; 2],
    manager: AttrStorageManager,
) -> CMap2<T> {
    let map: CMap2<T> = CMap2::new_with_undefined_attributes(4 * n_square_x * n_square_y, manager);

    // init beta functions
    (1..=(4 * n_square_x * n_square_y) as DartIdType)
        .zip(generate_square_beta_values(n_square_x, n_square_y))
        .for_each(|(dart, images)| {
            map.set_betas(dart, images);
        });

    // place vertices

    // bottow left vertex of all cells
    (0..n_square_y)
        // flatten the loop to expose more parallelism
        .flat_map(|y_idx| (0..n_square_x).map(move |x_idx| (y_idx, x_idx)))
        .for_each(|(y_idx, x_idx)| {
            let vertex_id = map.vertex_id((1 + x_idx * 4 + y_idx * 4 * n_square_x) as DartIdType);
            map.force_write_vertex(
                vertex_id,
                origin
                    + Vector2(
                        T::from(x_idx).unwrap() * len_per_x,
                        T::from(y_idx).unwrap() * len_per_y,
                    ),
            );
        });

    // top left vertex of all top row cells
    (0..n_square_x).for_each(|x_idx| {
        let y_idx = n_square_y - 1;
        let vertex_id = map.vertex_id((4 + x_idx * 4 + y_idx * 4 * n_square_x) as DartIdType);
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx).unwrap() * len_per_x,
                    T::from(y_idx + 1).unwrap() * len_per_y,
                ),
        );
    });

    // bottom right vertex of all right col cells
    (0..n_square_y).for_each(|y_idx| {
        let x_idx = n_square_x - 1;
        let vertex_id = map.vertex_id((2 + x_idx * 4 + y_idx * 4 * n_square_x) as DartIdType);
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx + 1).unwrap() * len_per_x,
                    T::from(y_idx).unwrap() * len_per_y,
                ),
        );
    });

    // top right vertex of the last cell
    {
        let (x_idx, y_idx) = (n_square_x - 1, n_square_y - 1);
        let vertex_id = map.vertex_id((3 + x_idx * 4 + y_idx * 4 * n_square_x) as DartIdType); // top right
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx + 1).unwrap() * len_per_x,
                    T::from(y_idx + 1).unwrap() * len_per_y,
                ),
        );
    }

    // check the number of built faces
    // this is set as debug only because the operation cost scales with map size
    // this can quickly overshadow the exectime of all previous code
    debug_assert_eq!(map.iter_faces().count(), n_square_x * n_square_y);

    map
}

#[allow(clippy::inline_always)]
#[rustfmt::skip]
#[inline(always)]
fn generate_square_beta_values(n_x: usize, n_y: usize) -> impl Iterator<Item = [DartIdType; 3]> {
    // this loop hierarchy yields the value in correct order
    // left to right first, then bottom to top
    (0..n_y).flat_map(move |iy| {
        (0..n_x).flat_map(move |ix| {
                let d1 = (1 + 4 * ix + n_x * 4 * iy) as DartIdType;
                let (d2, d3, d4) = (d1 + 1, d1 + 2, d1 + 3);
                // beta images of [d1, d2, d3, d4]
                [
                    [ d4, d2, if iy == 0     { 0 } else { d3 - 4 * n_x as DartIdType } ],
                    [ d1, d3, if ix == n_x-1 { 0 } else { d2 + 6                     } ],
                    [ d2, d4, if iy == n_y-1 { 0 } else { d1 + 4 * n_x as DartIdType } ],
                    [ d3, d1, if ix == 0     { 0 } else { d4 - 6                     } ],
                ]
                .into_iter()
            })
        })
}

/// Internal grid-building routine
#[allow(clippy::too_many_lines)]
pub fn build_2d_splitgrid<T: CoordsFloat>(
    origin: Vertex2<T>,
    [n_square_x, n_square_y]: [usize; 2],
    [len_per_x, len_per_y]: [T; 2],
    manager: AttrStorageManager,
) -> CMap2<T> {
    let map: CMap2<T> = CMap2::new_with_undefined_attributes(6 * n_square_x * n_square_y, manager);

    // init beta functions
    (1..=(6 * n_square_x * n_square_y) as DartIdType)
        .zip(generate_tris_beta_values(n_square_x, n_square_y))
        .for_each(|(dart, images)| {
            map.set_betas(dart, images);
        });

    // place vertices

    // bottow left vertex of all cells
    (0..n_square_y)
        // flatten the loop to expose more parallelism
        .flat_map(|y_idx| (0..n_square_x).map(move |x_idx| (y_idx, x_idx)))
        .for_each(|(y_idx, x_idx)| {
            let vertex_id = map.vertex_id((1 + x_idx * 6 + y_idx * 6 * n_square_x) as DartIdType);
            map.force_write_vertex(
                vertex_id,
                origin
                    + Vector2(
                        T::from(x_idx).unwrap() * len_per_x,
                        T::from(y_idx).unwrap() * len_per_y,
                    ),
            );
        });

    // top left vertex of all top row cells
    (0..n_square_x).for_each(|x_idx| {
        let y_idx = n_square_y - 1;
        let vertex_id = map.vertex_id((4 + x_idx * 6 + y_idx * 6 * n_square_x) as DartIdType);
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx).unwrap() * len_per_x,
                    T::from(y_idx + 1).unwrap() * len_per_y,
                ),
        );
    });

    // bottom right vertex of all right col cells
    (0..n_square_y).for_each(|y_idx| {
        let x_idx = n_square_x - 1;
        let vertex_id = map.vertex_id((2 + x_idx * 6 + y_idx * 6 * n_square_x) as DartIdType);
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx + 1).unwrap() * len_per_x,
                    T::from(y_idx).unwrap() * len_per_y,
                ),
        );
    });

    // top right vertex of the last cell
    {
        let (x_idx, y_idx) = (n_square_x - 1, n_square_y - 1);
        let vertex_id = map.vertex_id((6 + x_idx * 6 + y_idx * 6 * n_square_x) as DartIdType); // top right
        map.force_write_vertex(
            vertex_id,
            origin
                + Vector2(
                    T::from(x_idx + 1).unwrap() * len_per_x,
                    T::from(y_idx + 1).unwrap() * len_per_y,
                ),
        );
    }

    // check the number of built faces
    // this is set as debug only because the operation cost scales with map size
    // this can quickly overshadow the exectime of all previous code
    debug_assert_eq!(map.iter_faces().count(), 2 * n_square_x * n_square_y);

    map
}

#[allow(clippy::inline_always)]
#[rustfmt::skip]
#[inline(always)]
fn generate_tris_beta_values(n_x: usize, n_y: usize) -> impl Iterator<Item = [DartIdType; 3]> {
    // this loop hierarchy yields the value in correct order
    // left to right first, then bottom to top
    (0..n_y).flat_map(move |iy| {
        (0..n_x).flat_map(move |ix| {
                let d1 = (1 + 6 * ix + n_x * 6 * iy) as DartIdType;
                let (d2, d3, d4, d5, d6) = (d1 + 1, d1 + 2, d1 + 3, d1 + 4, d1 + 5);
                // beta images of [d1, d2, d3, d4]
                [
                    [ d3, d2, if iy == 0     { 0 } else { d6 - 6 * n_x as DartIdType } ],
                    [ d1, d3, d4                                                       ],
                    [ d2, d1, if ix == 0     { 0 } else { d5 - 6                     } ],
                    [ d6, d5, d2                                                       ],
                    [ d4, d6, if ix == n_x-1 { 0 } else { d3 + 6                     } ],
                    [ d5, d4, if iy == n_y-1 { 0 } else { d1 + 6 * n_x as DartIdType } ],
                ]
                .into_iter()
            })
        })
}