message: Don't refreshRenderer on material parameter changes.
  When only making parameter changes, it's not necessary to call
  refreshRenderer, which recreates the renderer.  Just update the
  cpp::Material list.
diff: @@ -804,7 +804,9 @@ void MainWindow::startNewOSPRayFrame()
  // child.
  if (baseMaterialRegistry->isModified()) {
  baseMaterialRegistry->commit();
  - refreshRenderer();
  + baseMaterialRegistry->updateMaterialList(rendererTypeStr);
  + auto &r = frame->childAs<sg::Renderer>("renderer");
  + r.createChildData("material", baseMaterialRegistry->cppMaterialList);
  frame->child("navMode") = true; // navMode is perfect for this
  }
  