WIP: position after a collision

html/images/space.svg

@@ -424,6 +424,13 @@
       });
     }
 
+    function perpIntxn(baseSlope, xa, ya, xc, yc) {
+      const altitudeSlope = 1 / -baseSlope;
+      const isx = (-altitudeSlope * xc + yc + baseSlope * xa - ya) / (baseSlope - altitudeSlope);
+      const isy = altitudeSlope * isx - altitudeSlope * xc + yc;
+      return { x: isx, y: isy };
+    }
+
     function drawLine(xa, ya, xb, yb) {
       const el = document.createElementNS(namespaceURIsvg, 'line');
       el.setAttribute('x1', xa);
@@ -455,40 +462,28 @@
 
       const baseSlope = slope({ xa, ya, xb, yb });
 
-      console.log("slope of base", baseSlope);
+      // console.log("slope of base", baseSlope);
 
       if (baseSlope === -Infinity) {
-        console.log("foot", xa + shipRadius, yc);
+        // console.log("foot", xa + shipRadius, yc);
       } else if (baseSlope === Infinity) {
-        console.log("foot", xa - shipRadius, yc);
+        // console.log("foot", xa - shipRadius, yc);
       } else if (Object.is(baseSlope, 0)) {
-        console.log("foot", xc, ya - shipRadius);
+        // console.log("foot", xc, ya - shipRadius);
       } else if (Object.is(baseSlope, -0)) {
-        console.log("foot", xc, ya + shipRadius);
+        // console.log("foot", xc, ya + shipRadius);
       } else {
-        console.log(xa, ya, xb, yb);
-        // 10, 40, 20, 20
-        // altitude slope (perpendicular of base)
-        const altitudeSlope = 1 / -baseSlope;
-        // point-slope formula
-        // y - ya = baseSlope * (x - xa)
-        // line equation of the base
-        // y = baseSlope * x - baseSlope * xa + ya
-        // y = -2x - (-2 * 10) + 40
-        // point-slope formula
-        // y - yc = altitudeSlope * (x - xc)
-        // line equation of the altitude
-        // y = altitudeSlope * x - altitudeSlope * xc + yc
-
-        // test point c 0, 20
-
-        // baseSlope * x - baseSlope * xa + ya = altitudeSlope * x - altitudeSlope * xc + yc
-        // baseSlope * x - altitudeSlope * x = -altitudeSlope * xc + yc + baseSlope * xa - ya
-        const isx = (-altitudeSlope * xc + yc + baseSlope * xa - ya) / (baseSlope - altitudeSlope);
-        const isy = altitudeSlope * isx - altitudeSlope * xc + yc;
-        // should be (35, 30)
-        console.log("foot coords", isx, isy);
-        drawLine(isx, isy, xc, yc);
+        const foot = perpIntxn(baseSlope, xa, ya, xc, yc);
+        // console.log("foot", foot);
+        // drawLine(foot.x, foot.y, xc, yc)
+        const el = document.createElementNS(namespaceURIsvg, 'line');
+        el.setAttribute('x1', foot.x);
+        el.setAttribute('y1', foot.y);
+        el.setAttribute('x2', xc);
+        el.setAttribute('y2', yc);
+        // this point should be the position of the ship to make it
+        // adjacent to the collision edge without overlapping it
+        console.log(el.getPointAtLength(5));
       }
 
       // https://en.wikipedia.org/wiki/Altitude_(triangle)#Altitude_in_terms_of_the_sides
@@ -584,7 +579,7 @@
         console.log("a", "position", position, s.position);
         s.velocity = { x: 0, y: 0 };
       } else if (s.collision) {
-        console.log("b", position, s.position);
+        console.log("b", s.position, s.collision);
 
         s.velocity = { x: 0, y: 0 };
         s.position.y = Math.trunc(s.collision.edge.ya - 5);