vtk-pure-rs 0.2.0

Pure Rust visualization toolkit — data structures, filters, I/O, rendering
Documentation 
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use crate::data::PolyData;

/// Compute mesh statistics: point count, cell count, area, edge stats.
#[derive(Debug, Clone)]
pub struct MeshMeasurements {
    pub num_points: usize,
    pub num_triangles: usize,
    pub num_quads: usize,
    pub num_other_polys: usize,
    pub num_lines: usize,
    pub total_area: f64,
    pub total_edge_length: f64,
    pub min_edge_length: f64,
    pub max_edge_length: f64,
    pub avg_edge_length: f64,
}

/// Measure a PolyData mesh comprehensively.
pub fn measure_mesh(input: &PolyData) -> MeshMeasurements {
    let mut num_tris = 0usize;
    let mut num_quads = 0usize;
    let mut num_other = 0usize;
    let mut total_area = 0.0;
    let mut min_edge = f64::MAX;
    let mut max_edge = 0.0f64;
    let mut sum_edge = 0.0;
    let mut edge_count = 0usize;

    for cell in input.polys.iter() {
        match cell.len() {
            3 => num_tris += 1,
            4 => num_quads += 1,
            n if n > 4 => num_other += 1,
            _ => {}
        }

        if cell.len() >= 3 {
            let v0 = input.points.get(cell[0] as usize);
            for i in 1..cell.len() - 1 {
                let v1 = input.points.get(cell[i] as usize);
                let v2 = input.points.get(cell[i+1] as usize);
                total_area += tri_area(v0, v1, v2);
            }
            for i in 0..cell.len() {
                let a = input.points.get(cell[i] as usize);
                let b = input.points.get(cell[(i+1)%cell.len()] as usize);
                let d = dist(a, b);
                min_edge = min_edge.min(d);
                max_edge = max_edge.max(d);
                sum_edge += d;
                edge_count += 1;
            }
        }
    }

    let mut total_line_len = 0.0;
    let mut num_lines = 0;
    for cell in input.lines.iter() {
        num_lines += 1;
        for i in 0..cell.len()-1 {
            total_line_len += dist(
                input.points.get(cell[i] as usize),
                input.points.get(cell[i+1] as usize),
            );
        }
    }

    if min_edge == f64::MAX { min_edge = 0.0; }

    MeshMeasurements {
        num_points: input.points.len(),
        num_triangles: num_tris,
        num_quads: num_quads,
        num_other_polys: num_other,
        num_lines: num_lines,
        total_area: total_area,
        total_edge_length: sum_edge + total_line_len,
        min_edge_length: min_edge,
        max_edge_length: max_edge,
        avg_edge_length: if edge_count > 0 { sum_edge / edge_count as f64 } else { 0.0 },
    }
}

fn tri_area(v0: [f64; 3], v1: [f64; 3], v2: [f64; 3]) -> f64 {
    let e1 = [v1[0]-v0[0], v1[1]-v0[1], v1[2]-v0[2]];
    let e2 = [v2[0]-v0[0], v2[1]-v0[1], v2[2]-v0[2]];
    let c = [e1[1]*e2[2]-e1[2]*e2[1], e1[2]*e2[0]-e1[0]*e2[2], e1[0]*e2[1]-e1[1]*e2[0]];
    0.5*(c[0]*c[0]+c[1]*c[1]+c[2]*c[2]).sqrt()
}

fn dist(a: [f64; 3], b: [f64; 3]) -> f64 {
    ((a[0]-b[0]).powi(2)+(a[1]-b[1]).powi(2)+(a[2]-b[2]).powi(2)).sqrt()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn measure_triangle() {
        let mut pd = PolyData::new();
        pd.points.push([0.0, 0.0, 0.0]);
        pd.points.push([1.0, 0.0, 0.0]);
        pd.points.push([0.0, 1.0, 0.0]);
        pd.polys.push_cell(&[0, 1, 2]);

        let m = measure_mesh(&pd);
        assert_eq!(m.num_points, 3);
        assert_eq!(m.num_triangles, 1);
        assert!((m.total_area - 0.5).abs() < 1e-10);
        assert!(m.min_edge_length > 0.0);
    }

    #[test]
    fn measure_quad() {
        let mut pd = PolyData::new();
        pd.points.push([0.0, 0.0, 0.0]);
        pd.points.push([1.0, 0.0, 0.0]);
        pd.points.push([1.0, 1.0, 0.0]);
        pd.points.push([0.0, 1.0, 0.0]);
        pd.polys.push_cell(&[0, 1, 2, 3]);

        let m = measure_mesh(&pd);
        assert_eq!(m.num_quads, 1);
        assert!((m.total_area - 1.0).abs() < 1e-10);
    }

    #[test]
    fn measure_with_lines() {
        let mut pd = PolyData::new();
        pd.points.push([0.0, 0.0, 0.0]);
        pd.points.push([3.0, 4.0, 0.0]);
        pd.lines.push_cell(&[0, 1]);

        let m = measure_mesh(&pd);
        assert_eq!(m.num_lines, 1);
        assert!((m.total_edge_length - 5.0).abs() < 1e-10);
    }

    #[test]
    fn empty_mesh() {
        let pd = PolyData::new();
        let m = measure_mesh(&pd);
        assert_eq!(m.num_points, 0);
        assert_eq!(m.total_area, 0.0);
    }
}