code: function() {
          var gl = this.context;
          gl.useProgram(this.shader);
          gl.bindBuffer(gl.ARRAY_BUFFER, this._attributeBuffer);
          var a,
              attributes = this.attributes;
          // Process every attribute
          for (var i = 0; i < attributes.length; i++) {
              a = attributes[i];
              gl.vertexAttribPointer(
                  a.location,
                  a.width,
                  a.type,
                  false,
                  this.stride * a.bytes,
                  a.offset * a.bytes
              );
          }
  
          // For now, special case the need for texture objects
          var t = this.texture_obj;
          if (t && t.unit === null) {
              this.layer.texture_manager.bindTexture(t);
          }
  
          this.index_pointer = 0;
      }
docs: Called before a batch of entities is prepped for rendering