How to pass information into Unreal Engine from outside source - rpc

Question

The Problem:
I want a high quality visualization of a simulation that I've built and runs on another application. Unreal Engine 4 has models that work, and renders nicely enough to fill my needs. The only problem, is I need to tell a running instance of an Unreal Engine project some of the information that my simulation is creating, like moving objects.
Potential solutions:
rpc plugin?
I'm reasonably familiar with grpc, and my simulation is set up so send and receive grpc messages, but I don't know how to implement grpc through unreal_engine. A couple others on the interweb have written rpc plugins, which might work for my needs. For example...
https://github.com/PaddleCreekGames/Proto3RPC_UE4
However, no idea how to take that pile of work done and actually use what I want. Needless to say, the documentation of that specific project is unfriendly to a user who didn't write it.
Something else?
If you have any ideas, or if you've historically passed information to unreal engine a specific way, any pointers in the right direction/code snippets/links to stuff I may have missed would be greatly appreciated.

Answer 1

I had the same question with theodox,
if the input doesn't have to happen instantly/in real-time.
You may for example update a parameter file for you simulation and read the parameters in your unreal engine application.
Here is an example to create the readFile bluemix function to read and parse an external JSON file:
in /Source/[Project name]/MyBlueprintFunctionLibrary.h, define output struct and function header
USTRUCT(BlueprintType)
struct FResultStruct
{
GENERATED_USTRUCT_BODY()
UPROPERTY(EditAnywhere,BlueprintReadWrite,Category = "Result Struct")
float fieldname1;
UPROPERTY(EditAnywhere,BlueprintReadWrite,Category = "Result Struct")
FString fieldname2;
//Constructor
FResultStruct()
{
fieldname1 = 0;
fieldname2 = "string";
}
};
UCLASS()
class EXPERIMENTALPROJECT_API UMyBlueprintFunctionLibrary : public UBlueprintFunctionLibrary
{
GENERATED_BODY()
public:
UFUNCTION(BlueprintCallable, Category = "MyBPLibrary")
static FResultStruct ReadFile(FString fileName);
};
in /Source/[Project name]/MyBlueprintFunctionLibrary.cpp implement your parameter file parser, for example:
// Read the results file
FResultStruct UMyBlueprintFunctionLibrary::ReadFile(FString fileName)
{
FString saveFilePath = FPaths::ConvertRelativePathToFull(FPaths::GameDir());
fileName = saveFilePath + fileName;
FResultStruct Result;
FString jsonString;
FFileHelper::LoadFileToString(jsonString, *fileName);
TSharedPtr<FJsonObject> JsonParsed;
TSharedRef<TJsonReader<TCHAR>> JsonReader = TJsonReaderFactory<TCHAR>::Create(jsonString);
if (FJsonSerializer::Deserialize(JsonReader, JsonParsed))
{
Result.fieldname1 = JsonParsed->GetNumberField("fieldname1");
Result.fieldname2 = JsonParsed->GetStringField("fieldname2");
}
return Result;
}
And in your unreal engine blueprint you can call this file reading function and use its parsed content in your application:
example
If you need live input, you may need to create HUD in UE4 and create input fields for all your parameters, that's more labor intensive imo.