message: add basic volume generator option in menu
diff: @@ -683,7 +683,7 @@ namespace ospray {
  ImGui::SameLine();
  static int which = 0;
  - ImGui::Combo("##1", &which, "spheres\0cube\0cylinders\0vtkWavelet\0\0", 4);
  + ImGui::Combo("##1", &which, "spheres\0cube\0cylinders\0volume\0vtkWavelet\0\0", 5);
  static std::string parameters;
  ImGui::Text("Generator Params: ");
  @@ -716,6 +716,9 @@ namespace ospray {
  type = "cylinders";
  break;
  case 3:
  + type = "volume";
  + break;
  + case 4:
  type = "vtkWavelet";
  break;
  default:
  