在JavaScript中簡單的三維粒子引力？

Question

我想在我的3D環境中做一些簡單的重力處理（我使用three.js）。我有一些代碼，但它不起作用。我希望這只是一個愚蠢的錯誤。 編輯：替換舊代碼

function handleGravity() { 
    for(var j = 0; j < spheres.length; j++) { 

     for(var i = 0; i < spheres.length; i++) { 

      var r1 = new Array(spheres[j].position.x, spheres[j].position.y, spheres[j].position.z); 
      var r2 = new Array(spheres[i].position.x, spheres[i].position.y, spheres[i].position.z); 
      var r12 = new Array(r2[0]-r1[0], r2[1]-r1[1], r2[2]-r1[2]); 
      var r12UnitVector = new Array(r12[0]/Math.abs(r12[0]), r12[1]/Math.abs(r12[1]),r12[2]/Math.abs(r12[2])); 

      var m1 = masses[j]; 
      var m2 = masses[i]; 
      var r12Squared = r12[0]*r12[0] + r12[1]*r12[1] + r12[2]*r12[2]; 
      var a12 = new Array(-(gravConst*m2/r12Squared)*r12UnitVector[0], -(gravConst*m2/r12Squared)*r12UnitVector[1], -(gravConst*m2/r12Squared)*r12UnitVector[2]); 

      velocities[j][0] += a12[0]*timePassed; 
      velocities[j][1] += a12[1]*timePassed; 
      velocities[j][2] += a12[2]*timePassed; 
     } 

    } 
} 

如果你能看到什麼毛病，或給我使用JavaScript在3D環境模擬許多顆粒最有效任何提示（我很新的物理+模擬），那會很棒！

Answer 1

這似乎工作：

function handleGravity() { 
    for(var j = 0; j < spheres.length; j++) { 

     for(var i = 0; i < spheres.length; i++) { 
      if(i != j) { 
       var r1 = new Array(spheres[j].position.x, spheres[j].position.y, spheres[j].position.z); 
       var r2 = new Array(spheres[i].position.x, spheres[i].position.y, spheres[i].position.z); 
       var r12 = new Array(r2[0]-r1[0], r2[1]-r1[1], r2[2]-r1[2]); 
       var r12UnitVector = new Array(r12[0]/Math.abs(r12[0] + r12[1] + r12[2])/3, r12[1]/Math.abs(r12[0] + r12[1] + r12[2])/3, r12[2]/Math.abs(r12[0] + r12[1] + r12[2])/3); 

       var m1 = masses[j]; 
       var m2 = masses[i]; 
       var r12Squared = r12[0]*r12[0] + r12[1]*r12[1] + r12[2]*r12[2]; 
       var a12 = new Array(-(gravConst*m2/r12Squared)*r12UnitVector[0], -(gravConst*m2/r12Squared)*r12UnitVector[1], -(gravConst*m2/r12Squared)*r12UnitVector[2]); 

       velocities[j][0] -= a12[0]*timePassed; 
       velocities[j][1] -= a12[1]*timePassed; 
       velocities[j][2] -= a12[2]*timePassed; 
      } 
     } 

    } 
}