message: gltf_baker now has an export modal.
diff: @@ -93,6 +93,7 @@ struct App {
  AppState pushedState;
  gltfio::AssetPipeline* pipeline;
  uint32_t bakeResolution = 1024;
  + bool preserveMaterialsForExport = true;
  // Secondary threads might write to the following fields.
  std::shared_ptr<std::string> statusText;
  @@ -626,8 +627,8 @@ int main(int argc, char** argv) {
  // Export action
  const bool canExport = app.state == BAKED;
  ImGui::PushStyleColor(ImGuiCol_Text, canExport ? enabled : disabled);
  - if (ImGui::Button("Export", ImVec2(100, 50)) && canExport) {
  - exportAsset(app);
  + if (ImGui::Button("Export...", ImVec2(100, 50)) && canExport) {
  + ImGui::OpenPopup("Export options");
  }
  if (ImGui::IsItemHovered()) {
  ImGui::SetTooltip("Saves the baked result to disk.");
  @@ -678,6 +679,16 @@ int main(int argc, char** argv) {
  }
  ImGui::PopStyleVar();
  }
  +
  + if (ImGui::BeginPopupModal("Export options", nullptr,
  + ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoTitleBar)) {
  + ImGui::Checkbox("Preserve materials", &app.preserveMaterialsForExport);
  + if (ImGui::Button("OK", ImVec2(120,0))) {
  + ImGui::CloseCurrentPopup();
  + exportAsset(app);
  + }
  + ImGui::EndPopup();
  + }
  });
  // Leave FXAA enabled but we also enable MSAA for a nice result. The wireframe looks
  