message: Add VSM control to SimpleViewer
diff: @@ -196,6 +196,7 @@ private:
  filament::math::float3 mSunlightDirection = {0.6, -1.0, -0.8};
  bool mEnableWireframe = false;
  bool mEnableSunlight = true;
  + bool mEnableVsm = false;
  bool mEnableShadows = true;
  int mShadowCascades = 1;
  bool mEnableContactShadows = false;
  @@ -483,6 +484,7 @@ void SimpleViewer::updateUserInterface() {
  ImGuiExt::DirectionWidget("Sun direction", mSunlightDirection.v);
  ImGui::Checkbox("Enable sunlight", &mEnableSunlight);
  ImGui::Checkbox("Enable shadows", &mEnableShadows);
  + ImGui::Checkbox("Enable VSM", &mEnableVsm);
  ImGui::SliderInt("Cascades", &mShadowCascades, 1, 4);
  ImGui::Checkbox("Debug Cascades", debug.getPropertyAddress<bool>("d.shadowmap.visualize_cascades"));
  ImGui::Checkbox("Enable contact shadows", &mEnableContactShadows);
  @@ -534,6 +536,8 @@ void SimpleViewer::updateUserInterface() {
  lm.setShadowCaster(ci, mEnableShadows);
  });
  + mView->setShadowType(mEnableVsm ? View::ShadowType::VSM : View::ShadowType::PCF);
  +
  if (mAsset != nullptr) {
  if (ImGui::CollapsingHeader("Hierarchy")) {
  ImGui::Indent();
  