Refactor

html/images/space.svg

@@ -91,8 +91,8 @@
       </g>
     </g>
 
-    <polygon id="wall" points="20,20 40,20 40,40 20,40" />
-    <!-- <polygon id="wall" points="-10,-30 -10,-40 30,-50 60,-30 80,0 150,0 150,10 60,50 -10,40 -20,20 20,20 20,-20" /> -->
+    <!-- <polygon id="wall" points="20,20 40,20 40,40 20,40" /> -->
+    <polygon id="wall" points="-10,-30 -10,-40 30,-50 60,-30 80,0 150,0 150,10 60,50 -10,40 -20,20 20,20 20,-20" />
 
     <g id="triangles"></g>
     <g id="lines"></g>
@@ -147,7 +147,7 @@
 
     const triangleContainer = document.querySelector('#triangles');
     const lineContainer = document.querySelector('#lines');
-    const trianglePts = points.map((pt, i) => [pt, points[(i + 1) % points.length]]);
+    const edgePts = points.map((pt, i) => [pt, points[(i + 1) % points.length]]);
     const drawCollisionLines = false;
 
     function drawEdges(lpts) {
@@ -167,7 +167,7 @@
       });
     }
 
-    drawEdges(trianglePts);
+    drawEdges(edgePts);
 
     function drawTriangles(container, pts, [positionX, positionY]) {
       pts.forEach(([[x1, y1], [x2, y2]]) => {
@@ -178,7 +178,7 @@
       });
     }
 
-    drawTriangles(triangleContainer, trianglePts, position);
+    drawTriangles(triangleContainer, edgePts, position);
     const triangles = triangleContainer.querySelectorAll('polygon');
 
     // Triangle has a clockwise orientation
@@ -209,7 +209,7 @@
       }, []);
     }
 
-    const collisionEdges = findEdges(trianglePts, position);
+    const collisionEdges = findEdges(edgePts, position);
 
     function updateTriangles([positionX, positionY]) {
       const delim = ' ';
@@ -339,39 +339,29 @@
       });
     }
 
-    function detectCollision(points, visibleTriangles) {
+    function detectCollision(points, [xc, yc], edges) {
       const cornerCollision = points.some(([x, y]) => {
-        cornerPt.x = x - positionX;
-        cornerPt.y = y - positionY;
+        cornerPt.x = x - xc;
+        cornerPt.y = y - yc;
 
         return shipBody.isPointInFill(cornerPt);
       });
 
       const shipRadius = 5;
-      const sideCollision = [...visibleTriangles].reduce((acc, t) => {
-        const [[ax, ay], [bx, by], [shipx, shipy]] =
-          t.getAttribute('points').split(' ').map(n => n.split(',').map(n => +n));
+      const sideCollision = edges.reduce((acc, e) => {
+        const [[xa, ya], [xb, yb]] = e.split(' ').map(n => n.split(',').map(n => +n));
 
-        const da = distance(ax, ay, shipx, shipy);
-        const db = distance(bx, by, shipx, shipy);
+        const da = distance(xa, ya, xc, yc);
+        const db = distance(xb, yb, xc, yc);
         // TODO: calculate this one ahead of time
-        const dc = distance(ax, ay, bx, by);
+        const dc = distance(xa, ya, xb, yb);
 
         // https://en.wikipedia.org/wiki/Altitude_(triangle)#Altitude_in_terms_of_the_sides
         // Find altitude of side c (the base)
         const s = (1 / 2) * (da + db + dc);
         const hc = (2 / dc) * Math.sqrt(s * (s - da) * (s - db) * (s - dc));
 
-        // https://en.wikipedia.org/wiki/Law_of_cosines
-        // Solve for angles alpha and beta with inverse cosine (arccosine) function
-        const alpha = Math.acos((db**2 + dc**2 - da**2) / (2 * db * dc));
-        const beta = Math.acos((da**2 + dc**2 - db**2) / (2 * da * dc));
-
-        // Is acute if both angles are < 90 degrees
-        // TODO: what about right triangles?
-        const isAcute = alpha < halfPi && beta < halfPi;
-
-        return isAcute ? [...acc, hc] : acc;
+        return [...acc, hc];
       }, []).some(h => h <= shipRadius);
 
       return cornerCollision || sideCollision;
@@ -409,6 +399,25 @@
       return position;
     }
 
+    function updateEdges(position) {
+      const mappedEdges = findEdges(edgePts, position);
+
+      [...lineContainer.children].forEach(l => {
+        const x1 = l.getAttribute('x1');
+        const y1 = l.getAttribute('y1');
+        const x2 = l.getAttribute('x2');
+        const y2 = l.getAttribute('y2');
+        const edge = `${x1},${y1} ${x2},${y2}`;
+
+        if (mappedEdges.includes(edge))
+          if ([
+            lineContainer.childElementCount <= collisionEdges.length,
+            !collisionEdges.includes(edge)
+          ].some(c => c))
+            l.remove();
+      });
+    }
+
     let start;
     let restart = false;
     function firstFrame(timestamp) {
@@ -449,38 +458,15 @@
 
       position = updateShip(elapsed);
       updateBullets(elapsed);
-
-      const visibleTriangles = updateTriangles(position);
-      const visibleTrianglePoints = [...visibleTriangles].map(p => p.getAttribute("points"));
-
-      const mappedEdges = visibleTrianglePoints.map(vt => {
-        vt = vt.split(' ');
-        vt.pop();
-        return vt.join(' ');
-      });
-
-      [...lineContainer.children].forEach(l => {
-        const x1 = l.getAttribute('x1');
-        const y1 = l.getAttribute('y1');
-        const x2 = l.getAttribute('x2');
-        const y2 = l.getAttribute('y2');
-        const str = `${x1},${y1} ${x2},${y2}`;
-
-        if (mappedEdges.includes(str))
-          if ([
-            lineContainer.childElementCount <= collisionEdges.length,
-            !collisionEdges.includes(str)
-          ].some(c => c))
-            l.remove();
-      });
+      updateEdges(position);
 
       if (restart) {
         restart = false;
         [...lineContainer.children].forEach(c => c.remove());;
-        drawEdges(trianglePts);
+        drawEdges(edgePts);
       }
 
-      const collision = detectCollision(points, visibleTriangles);
+      const collision = detectCollision(points, position, findEdges(edgePts, position));
       wall.setAttribute('fill', collision ? 'red' : 'black');
 
       if (collision) {