code: public Matrix4 set (DoubleBuffer buf) {
          m00 = buf.get(); m01 = buf.get(); m02 = buf.get(); m03 = buf.get();
          m10 = buf.get(); m11 = buf.get(); m12 = buf.get(); m13 = buf.get();
          m20 = buf.get(); m21 = buf.get(); m22 = buf.get(); m23 = buf.get();
          m30 = buf.get(); m31 = buf.get(); m32 = buf.get(); m33 = buf.get();
          return this;
      }
docs: Sets the contents of this matrix from the supplied (column-major) buffer.
  
  @return a reference to this matrix, for chaining.