From 2f2a82c46f68ec8e6f831b424f97ce719bdeb915 Mon Sep 17 00:00:00 2001
From: Catalin Constantin Mititiuc <webdevcat@proton.me>
Date: Sun, 4 Jan 2026 18:50:17 -0800
Subject: [PATCH] Fix edges facing ship calc

---
 html/images/space.svg | 53 ++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 21 deletions(-)

diff --git a/html/images/space.svg b/html/images/space.svg
index 23cf20c..bf05f88 100644
--- a/html/images/space.svg
+++ b/html/images/space.svg
@@ -210,8 +210,8 @@
       position: { x: 0, y: 0 },
       // velocity: { x: 0, y: 0 },
 
-      velocity: { x: 5, y: 10 },
-      // velocity: { x: 10*mult, y: 10*mult },
+      // velocity: { x: 5, y: 10 },
+      velocity: { x: 5*mult, y: 10*mult },
       acceleration: { x: 0, y: 0 },
       rotate: 0,
       collision: null,
@@ -817,28 +817,40 @@
       return cl.getPointAtLength(b);
     }
 
-    function collisionPosition(edge, position, velocity, radius) {
+    function edgeCollisionPosition(xc, yc, x, y, edge, radius) {
       const baseSlope = slope(edge);
       // if (Object.is(baseSlope, 0)) s.isLanded = true;
 
-      const { xa, ya, xb, yb } = edge;
-      const baseLine = { x1: xa, y1: ya, x2: xb, y2: yb };
+      let { xa, ya, xb, yb } = edge;
+
+      const rise = yb - ya;
+      const run = xb - xa;
+      const length = distance(xa, ya, xb, yb);
+
+      const riol = rise / length * radius;
+      const ruol = run / length * radius;
+
+      const edgeSeg = { xa: xa + riol, ya: ya - ruol, xb: xb + riol, yb: yb - ruol};
+
+      // const { xa: x1, ya: y1, xb: x2, yb: y2 } = positionSeg;
+      // const { xa: x3, ya: y3, xb: x4, yb: y4 } = edgeSeg;
+
+      // const baseLine = { x1: xa, y1: ya, x2: xb, y2: yb };
+      const baseLine = { x1: edgeSeg.xa, y1: edgeSeg.ya, x2: edgeSeg.xb, y2: edgeSeg.yb };
 
       const velocityLine = {
-        x1: position.x,
-        y1: position.y,
-        x2: position.x + velocity.x,
-        y2: position.y + velocity.y
+        x1: x,
+        y1: y,
+        x2: xc,
+        y2: yc
       };
 
-      // console.log("COLLISION DETECTED", s.collision);
-
       // console.log("baseSlope", baseSlope);
-      const baseNrmlIntxn = perpIntxn(baseSlope, xa, ya, position.x, position.y);
+      const baseNrmlIntxn = perpIntxn(baseSlope, xa, ya, x, y);
       const baseVelIntxn = lineIntxnPt(baseLine, velocityLine);
       // console.log("baseNrmlIntxn", baseNrmlIntxn, "baseVelIntxn", baseVelIntxn);
       const baseSegLength = distance(baseNrmlIntxn.x, baseNrmlIntxn.y , baseVelIntxn.x, baseVelIntxn.y);
-      const normalSegLength = distance(baseNrmlIntxn.x, baseNrmlIntxn.y, position.x, position.y);
+      const normalSegLength = distance(baseNrmlIntxn.x, baseNrmlIntxn.y, x, y);
       // console.log("baseSegLength", baseSegLength, "normalSegLength", normalSegLength);
       const theta = Math.atan(normalSegLength / baseSegLength);
       const shipRadius = radius;
@@ -847,10 +859,9 @@
       const cl = document.createElementNS(namespaceURIsvg, 'line');
       cl.setAttribute('x1', baseVelIntxn.x);
       cl.setAttribute('y1', baseVelIntxn.y);
-      cl.setAttribute('x2', position.x);
-      cl.setAttribute('y2', position.y);
+      cl.setAttribute('x2', x);
+      cl.setAttribute('y2', y);
 
-      // console.log("h", h, "theta", theta);
       const clPos = cl.getPointAtLength(h);
       return clPos;
     }
@@ -896,8 +907,7 @@
 
       const efs = mes.filter(({ edge, wall }) => {
         const { xa, ya, xb, yb } = edge;
-        // console.log("xa", xa, "ya", ya, "xb", xb, "yb", yb);
-        const det = (xb - xa) * (yc - ya) - (xc - xa) * (yb - ya);
+        const det = (xb - xa) * (y - ya) - (x - xa) * (yb - ya);
         return det < 0;
       });
       console.log("edges facing ship", efs);
@@ -927,11 +937,12 @@
         const s = ((x3-x1)*(y4-y3)-(x4-x3)*(y3-y1))/((x2-x1)*(y4-y3)-(x4-x3)*(y2-y1));
         const t = -((x2-x1)*(y3-y1)-(x3-x1)*(y2-y1))/((x2-x1)*(y4-y3)-(x4-x3)*(y2-y1));
         const roundedT = +t.toFixed(2);
+        const roundedS = +s.toFixed(2);
 
         console.log("positionSeg", positionSeg, "edgeSeg", edgeSeg);
-        console.log("s", s, "t", roundedT);
+        console.log("s", roundedS, "t", roundedT);
 
-        return s <= 1 && roundedT >= 0;
+        return roundedS <= 1 && roundedT >= 0;
       });
 
       efs.forEach(({ edge, wall }) => {
@@ -999,7 +1010,7 @@
         if (s.collision.corner) {
           posP = cornerContactPosition(xc, yc, x, y, s.collision.corner, shipRadius);
         } else if (s.collision.edge) {
-          posP = collisionPosition(s.collision.edge, s.position, s.velocity, shipRadius);
+          posP = edgeCollisionPosition(xc, yc, x, y, s.collision.edge, shipRadius);
         }
 
         s.velocity = { x: 0, y: 0 };