refactor: minor refactorings

Author: zOadT

src/collision/Distance.ts

@@ -112,7 +112,6 @@ export const Distance = function (output: DistanceOutput, cache: SimplexCache, i
   let saveCount = 0;
 
   let distanceSqr1 = Infinity;
-  let distanceSqr2 = Infinity;
 
   // Main iteration loop.
   let iter = 0;
@@ -133,7 +132,7 @@ export const Distance = function (output: DistanceOutput, cache: SimplexCache, i
 
     // Compute closest point.
     const p = simplex.getClosestPoint();
-    distanceSqr2 = p.lengthSquared();
+    const distanceSqr2 = p.lengthSquared();
 
     // Ensure progress
     if (distanceSqr2 >= distanceSqr1) {

src/collision/shape/ChainShape.ts

@@ -148,6 +148,10 @@ export class ChainShape extends Shape {
   _createLoop(vertices: Vec2Value[]): ChainShape {
     _ASSERT && console.assert(this.m_vertices.length == 0 && this.m_count == 0);
     _ASSERT && console.assert(vertices.length >= 3);
+    if (vertices.length < 3) {
+      return;
+    }
+
     for (let i = 1; i < vertices.length; ++i) {
       const v1 = vertices[i - 1];
       const v2 = vertices[i];

src/dynamics/Contact.ts

@@ -39,6 +39,7 @@ import { ContactImpulse, TimeStep } from "./Solver";
 const _ASSERT = typeof ASSERT === 'undefined' ? false : ASSERT;
 
 
+// Solver debugging is normally disabled because the block solver sometimes has to deal with a poorly conditioned effective mass matrix.
 const DEBUG_SOLVER = false;
 
 /**
@@ -910,8 +911,7 @@ export class Contact {
       // 01/07 on Box2D_Lite).
       // Build the mini LCP for this contact patch
       //
-      // vn = A * x + b, vn >= 0, , vn >= 0, x >= 0 and vn_i * x_i = 0 with i =
-      // 1..2
+      // vn = A * x + b, vn >= 0, x >= 0 and vn_i * x_i = 0 with i = 1..2
       //
       // A = J * W * JT and J = ( -n, -r1 x n, n, r2 x n )
       // b = vn0 - velocityBias