Do not create an imgui.ini file.

Added help text.
Added image to README.

Author: GPSnoopy

LucySettings.jpg

@@ -1,5 +1,7 @@
 # Ray Tracing In Vulkan
 
+<img align="center" src="https://github.com/GPSnoopy/RayTracingInVulkan/blob/master/LucySettings.jpg">
+
 My implementation of [Peter Shirley's Ray Tracing in One Weekend](https://github.com/petershirley/raytracinginoneweekend) book using Vulkan and NVIDIA's RTX extension (VK_NV_ray_tracing). This allows most scenes to render at interactive speed on appropriate hardware.
 
 This real-time ray tracer can also load full geometry from OBJ files as well as render the procedural spheres from the book. An accumulation buffer is used to increase the sample count when the camera is not moving while keeping the frame rate interactive. I have added a UI built using [Dear ImGui](https://github.com/ocornut/imgui) to allow changing the renderer parameters on the fly. Unlike projects such as [Q2VKPT](http://brechpunkt.de/q2vkpt/), there is no denoising filter. So the image will get noisy when moving the camera.

README.md

@@ -74,6 +74,11 @@ UserInterface::UserInterface(
 		Throw(std::runtime_error("failed to initialise ImGui vulkan adapter"));
 	}
 
+	auto& io = ImGui::GetIO();
+
+	// No ini file.
+	io.IniFilename = nullptr;
+
 	// DPI
 	const auto dpi = window.Dpi();
 	const auto scaleFactor = static_cast<float>(dpi / 110);
@@ -82,8 +87,6 @@ UserInterface::UserInterface(
 	ImGui::GetStyle().ScaleAllSizes(scaleFactor);
 
 	// Upload ImGui fonts
-	auto& io = ImGui::GetIO();
-
 	if (!io.Fonts->AddFontFromFileTTF("../assets/fonts/Cousine-Regular.ttf", 13 * scaleFactor))
 	{
 		Throw(std::runtime_error("failed to load ImGui font"));
@@ -174,6 +177,13 @@ void UserInterface::DrawSettings()
 			scenes.push_back(scene.first.c_str());
 		}
 
+		ImGui::Text("Help");
+		ImGui::Separator();
+		ImGui::BulletText("Press F1 to toggle Settings.");
+		ImGui::BulletText("Press F2 to toggle Statistics.");
+		ImGui::BulletText("Press R to toggle ray tracing.");
+		ImGui::NewLine();
+
 		ImGui::Text("Scene");
 		ImGui::Separator();
 		ImGui::PushItemWidth(-1);