javascript - Cylinder partially visible WebGL -

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i designing cylinder in webgl 1.0 (which based on opengl es 2.0).

it started off n-sided polygon (n slices) m stacks. normals specified follows:

enter image description here

even though polygon/cylinder being drawn correctly, faces aren't visible every angle. can seen inside following images show:

enter image description here

enter image description here

my goal have visible cylinder following 1 (no top/bottom faces required):

enter image description here

does have idea on how fix this? code below:

//end if stacks = 0  if (this.stacks <= 0) return;   this.vertices = [];   this.indices = [];  this.normals = [];  //--- vertices & normals ---   var angle;  var alpha = 360 / this.slices;  var zcoord = 0;   // (n) stacks -> (n + 1) faces -> (faces * this.slices) vertex  ( var stackindex = 0; stackindex < this.stacks + 1; stackindex++) {       //reset angle each face of stack      angle = 0;       ( var sliceindex = 0; sliceindex < this.slices; sliceindex++) {           this.vertices.push(math.cos(angle * degtorad)); //x          this.vertices.push(math.sin(angle * degtorad)); //y          this.vertices.push(zcoord); //z           this.normals.push(math.cos(angle * degtorad)); //x          this.normals.push(math.sin(angle * degtorad)); //y          this.normals.push(zcoord); //z           //updating angle          angle = angle + alpha;           }      //updating z coordinate      zcoord = zcoord + (1 / this.stacks);  }     //--- indices ---   var stackinc; stackindex = 0; sliceindex = 0;   (stackindex = 0; stackindex < this.stacks; stackindex++) {       stackinc = stackindex * this.slices;       (sliceindex = 0; sliceindex < this.slices; sliceindex++) {           if (sliceindex != this.slices - 1) {               //t1              this.indices.push(sliceindex + stackinc);              this.indices.push(sliceindex + stackinc + this.slices);              this.indices.push(sliceindex + stackinc + this.slices + 1);               //t2              this.indices.push(sliceindex + stackinc + this.slices + 1); //this.slices              this.indices.push(sliceindex + stackinc + 1); //0              this.indices.push(sliceindex + stackinc); //int4              }         //handling last face uses repeated vertices          else {              this.indices.push(sliceindex + stackinc);              this.indices.push(sliceindex + stackinc + this.slices);              this.indices.push(stackinc + this.slices);               this.indices.push(stackinc + this.slices);              this.indices.push(stackinc);              this.indices.push(sliceindex + stackinc); //int4              }          }      }

regardless of face normals, webgl defines front- , back-face based on order in define triangle.

having triangle:

a-------b  \     /   \   /    \ /     c

if add vertices index in order a, b, c (clock wise), , don't see them, need switch order in a, c, b (counter clock wise).

this because of this: https://www.opengl.org/wiki/face_culling


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