feat(geom-clip-line): add clipLinePoly(), update deps

thi-ng · Jun 20, 2020 · e096efd · e096efd
1 parent 6958280
commit e096efd
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Showing 4 changed files with 143 additions and 114 deletions.
diff --git a/packages/geom-clip-line/package.json b/packages/geom-clip-line/package.json
@@ -43,6 +43,7 @@
         "typescript": "^3.9.2"
     },
     "dependencies": {
+        "@thi.ng/geom-isec": "^0.4.21",
         "@thi.ng/vectors": "^4.4.4",
         "tslib": "^1.12.0"
     },

diff --git a/packages/geom-clip-line/src/clip-poly.ts b/packages/geom-clip-line/src/clip-poly.ts
@@ -0,0 +1,26 @@
+import { intersectRayPolylineAll } from "@thi.ng/geom-isec";
+import { direction, ReadonlyVec, Vec } from "@thi.ng/vectors";
+
+/**
+ * Computes all intersection points of the infinite line defined by `a`,
+ * `b` with the given polygon. Returns an array of segments where the
+ * line is inside the polygon.
+ *
+ * @param a
+ * @param b
+ * @param pts
+ */
+export const clipLinePoly = (
+    a: ReadonlyVec,
+    b: ReadonlyVec,
+    pts: ReadonlyVec[]
+) => {
+    const isecs = intersectRayPolylineAll(a, direction([], a, b), pts, true)
+        .isec;
+    if (!isecs) return;
+    const segments: Vec[][] = [];
+    for (let i = 0; i < isecs.length; i += 2) {
+        segments.push([<Vec>isecs[i], <Vec>isecs[i + 1]]);
+    }
+    return segments;
+};
diff --git a/packages/geom-clip-line/src/index.ts b/packages/geom-clip-line/src/index.ts
@@ -1,114 +1,2 @@
-import type { Vec, ReadonlyVec } from "@thi.ng/vectors";
-
-/**
- * Performs Liang-Barsky clipping of the line segment with endpoints
- * `a`, `b` against the clipping rect defined by `min` and `max`. The
- * optional `ca` and `cb` vectors can be given to store the result
- * (clipped points). If omitted creates new vectors. Returns a tuple of
- * `[ca, cb, a, b]`, where the latter two values represent the
- * normalized distances of the clipped points relative to original given
- * line segment. Returns `undefined` iff the line lies completely
- * outside the rect.
- *
- * - {@link https://en.wikipedia.org/wiki/Liang%E2%80%93Barsky_algorithm}
- * - {@link https://github.com/thi-ng/c-thing/blob/develop/src/geom/clip/liangbarsky.c}
- *
- * @param a - line endpoint
- * @param b - line endpoint
- * @param min - bbox min
- * @param max - bbox max
- * @param ca - result A
- * @param cb - result B
- */
-export const liangBarsky2 = (
-    a: ReadonlyVec,
-    b: ReadonlyVec,
-    min: ReadonlyVec,
-    max: ReadonlyVec,
-    ca: Vec = [],
-    cb: Vec = []
-): [Vec, Vec, number, number] | undefined => {
-    const res = liangBarsky2Raw(
-        a[0],
-        a[1],
-        b[0],
-        b[1],
-        min[0],
-        min[1],
-        max[0],
-        max[1]
-    );
-    if (!res) return;
-
-    ca[0] = res[0];
-    ca[1] = res[1];
-    cb[0] = res[2];
-    cb[1] = res[3];
-
-    return [ca, cb, res[4], res[5]];
-};
-
-/**
- * Same as {@link liangBarsky2} but for non-vector arguments.
- *
- * @param ax
- * @param ay
- * @param bx
- * @param by
- * @param minx
- * @param miny
- * @param maxx
- * @param maxy
- */
-export const liangBarsky2Raw = (
-    ax: number,
-    ay: number,
-    bx: number,
-    by: number,
-    minx: number,
-    miny: number,
-    maxx: number,
-    maxy: number
-): [number, number, number, number, number, number] | undefined => {
-    const dx = bx - ax;
-    const dy = by - ay;
-    let alpha = 0;
-    let beta = 1;
-
-    const clip = (p: number, q: number) => {
-        if (p < 0) {
-            const r = q / p;
-            if (r > beta) {
-                return false;
-            }
-            if (r > alpha) {
-                alpha = r;
-            }
-        } else if (p > 0) {
-            const r = q / p;
-            if (r < alpha) {
-                return false;
-            }
-            if (r < beta) {
-                beta = r;
-            }
-        } else if (q < 0) {
-            return false;
-        }
-        return true;
-    };
-
-    return clip(-dx, ax - minx) &&
-        clip(dx, maxx - ax) &&
-        clip(-dy, ay - miny) &&
-        clip(dy, maxy - ay)
-        ? [
-              alpha * dx + ax,
-              alpha * dy + ay,
-              beta * dx + ax,
-              beta * dy + ay,
-              alpha,
-              beta,
-          ]
-        : undefined;
-};
+export * from "./clip-poly";
+export * from "./liang-barsky";
diff --git a/packages/geom-clip-line/src/liang-barsky.ts b/packages/geom-clip-line/src/liang-barsky.ts
@@ -0,0 +1,114 @@
+import type { Vec, ReadonlyVec } from "@thi.ng/vectors";
+
+/**
+ * Performs Liang-Barsky clipping of the line segment with endpoints
+ * `a`, `b` against the clipping rect defined by `min` and `max`. The
+ * optional `ca` and `cb` vectors can be given to store the result
+ * (clipped points). If omitted creates new vectors. Returns a tuple of
+ * `[ca, cb, a, b]`, where the latter two values represent the
+ * normalized distances of the clipped points relative to original given
+ * line segment. Returns `undefined` iff the line lies completely
+ * outside the rect.
+ *
+ * - {@link https://en.wikipedia.org/wiki/Liang%E2%80%93Barsky_algorithm}
+ * - {@link https://github.com/thi-ng/c-thing/blob/develop/src/geom/clip/liangbarsky.c}
+ *
+ * @param a - line endpoint
+ * @param b - line endpoint
+ * @param min - bbox min
+ * @param max - bbox max
+ * @param ca - result A
+ * @param cb - result B
+ */
+export const liangBarsky2 = (
+    a: ReadonlyVec,
+    b: ReadonlyVec,
+    min: ReadonlyVec,
+    max: ReadonlyVec,
+    ca: Vec = [],
+    cb: Vec = []
+): [Vec, Vec, number, number] | undefined => {
+    const res = liangBarsky2Raw(
+        a[0],
+        a[1],
+        b[0],
+        b[1],
+        min[0],
+        min[1],
+        max[0],
+        max[1]
+    );
+    if (!res) return;
+
+    ca[0] = res[0];
+    ca[1] = res[1];
+    cb[0] = res[2];
+    cb[1] = res[3];
+
+    return [ca, cb, res[4], res[5]];
+};
+
+/**
+ * Same as {@link liangBarsky2} but for non-vector arguments.
+ *
+ * @param ax
+ * @param ay
+ * @param bx
+ * @param by
+ * @param minx
+ * @param miny
+ * @param maxx
+ * @param maxy
+ */
+export const liangBarsky2Raw = (
+    ax: number,
+    ay: number,
+    bx: number,
+    by: number,
+    minx: number,
+    miny: number,
+    maxx: number,
+    maxy: number
+): [number, number, number, number, number, number] | undefined => {
+    const dx = bx - ax;
+    const dy = by - ay;
+    let alpha = 0;
+    let beta = 1;
+
+    const clip = (p: number, q: number) => {
+        if (p < 0) {
+            const r = q / p;
+            if (r > beta) {
+                return false;
+            }
+            if (r > alpha) {
+                alpha = r;
+            }
+        } else if (p > 0) {
+            const r = q / p;
+            if (r < alpha) {
+                return false;
+            }
+            if (r < beta) {
+                beta = r;
+            }
+        } else if (q < 0) {
+            return false;
+        }
+        return true;
+    };
+
+    return clip(-dx, ax - minx) &&
+        clip(dx, maxx - ax) &&
+        clip(-dy, ay - miny) &&
+        clip(dy, maxy - ay)
+        ? [
+              alpha * dx + ax,
+              alpha * dy + ay,
+              beta * dx + ax,
+              beta * dy + ay,
+              alpha,
+              beta,
+          ]
+        : undefined;
+};