Added a method for checking if a renderer exists, just to prevent hacks.

Source/DFPSR/api/modelAPI.cpp

@@ -249,6 +249,10 @@ Renderer renderer_create() {
 	return std::make_shared<RendererImpl>();
 }
 
+bool renderer_exists(const Renderer& renderer) {
+	return renderer.get() != nullptr;
+}
+
 void renderer_begin(Renderer& renderer, ImageRgbaU8& colorBuffer, ImageF32& depthBuffer) {
 	MUST_EXIST(renderer,renderer_begin);
 	renderer->beginFrame(colorBuffer, depthBuffer);

Source/DFPSR/api/modelAPI.h

@@ -96,6 +96,7 @@ namespace dsr {
 	//     create (begin giveTask* end)*
 	Renderer renderer_create();
 	// Begin rendering to target color and depth buffers of the same dimensions
+	bool renderer_exists(const Renderer& renderer);
 	void renderer_begin(Renderer& renderer, ImageRgbaU8& colorBuffer, ImageF32& depthBuffer);
 	// Once an object passed game-specific occlusion tests, give it to the renderer using renderer_giveTask
 	// The render job will be performed during the next call to renderer_execute