code: function(e) {
          if (this._registryHoles.length === 0) {
              if (this._registrySize >= this.max_size) {
                  throw "Number of entities exceeds maximum limit.";
              } else if (this._registrySize >= this.array_size) {
                  this.growArrays(2 * this.array_size);
              }
              e._glBufferIndex = this._registrySize;
              this._registrySize++;
          } else {
              e._glBufferIndex = this._registryHoles.pop();
          }
      }
docs: Add an entity that needs to be rendered by this program Needs to be assigned an index in the buffer