西国街道・芥川宿の都市構造と防犯環境設計（CPTED）の科学：見通し・領域性・地域のつながりが生む安全なまちづくりと情報セキュリティの共通原理

{`//! CPTED (Crime Prevention Through Environmental Design) Spatial Optics & Visibility Engine.
//! Evaluates horizontal/vertical street illuminance (JIS Z 9126) and line-of-sight occlusion.

#[derive(Debug, Clone, Copy)]
pub struct StreetLight {
    pub x: f64,
    pub y: f64,
    pub height_m: f64,
    pub intensity_cd: f64,
}

#[derive(Debug, Clone, Copy)]
pub struct WallSegment {
    pub x1: f64,
    pub y1: f64,
    pub x2: f64,
    pub y2: f64,
}

#[derive(Debug, Clone, Copy, PartialEq)]
pub struct CptedPointReport {
    pub horizontal_lx: f64,
    pub vertical_face_lx: f64,
    pub visible_lights: usize,
    pub meets_jis_class_a: bool,
}

/// Checks whether the line segment P -> Q intersects a wall segment W.
#[inline]
pub fn segments_intersect(px: f64, py: f64, qx: f64, qy: f64, w: &WallSegment) -> bool {
    let ccw = |ax: f64, ay: f64, bx: f64, by: f64, cx: f64, cy: f64| -> f64 {
        (bx - ax) * (cy - ay) - (by - ay) * (cx - ax)
    };
    let d1 = ccw(px, py, qx, qy, w.x1, w.y1);
    let d2 = ccw(px, py, qx, qy, w.x2, w.y2);
    let d3 = ccw(w.x1, w.y1, w.x2, w.y2, px, py);
    let d4 = ccw(w.x1, w.y1, w.x2, w.y2, qx, qy);
    ((d1 > 0.0 && d2 < 0.0) || (d1 < 0.0 && d2 > 0.0))
        && ((d3 > 0.0 && d4 < 0.0) || (d3 < 0.0 && d4 > 0.0))
}

/// Evaluates horizontal and vertical illuminance at point (x, y) considering wall occlusions.
pub fn evaluate_cpted_point(
    x: f64,
    y: f64,
    lights: &[StreetLight],
    walls: &[WallSegment],
    maintenance_factor: f64,
) -> CptedPointReport {
    let m = maintenance_factor.clamp(0.1, 1.0);
    let face_z = 1.5_f64; — Standard pedestrian facial recognition height (1.5m)
    let mut e_h = 0.0_f64;
    let mut e_v = 0.0_f64;
    let mut visible_count = 0usize;

    for light in lights {
        let occluded = walls
            .iter()
            .any(|w| segments_intersect(x, y, light.x, light.y, w));
        if occluded {
            continue;
        }
        visible_count += 1;

        let dx = x - light.x;
        let dy = y - light.y;
        let r_sq = dx * dx + dy * dy;
        let r = r_sq.sqrt();

        // Horizontal illuminance on ground plane (z = 0): E_h = I * h / (h^2 + r^2)^(3/2)
        let d_ground_sq = light.height_m * light.height_m + r_sq;
        e_h += m * (light.intensity_cd * light.height_m) / d_ground_sq.powf(1.5);

        // Vertical illuminance at pedestrian face height (z = 1.5m): E_v = I * r / ((h - z_f)^2 + r^2)^(3/2)
        let dz = (light.height_m - face_z).max(0.5);
        let d_face_sq = dz * dz + r_sq;
        e_v += m * (light.intensity_cd * r) / d_face_sq.powf(1.5);
    }

    CptedPointReport {
        horizontal_lx: e_h,
        vertical_face_lx: e_v,
        visible_lights: visible_count,
        meets_jis_class_a: e_h >= 5.0 && e_v >= 1.0,
    }
}`}