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Problem binding Shader Parameter to VertexFactory

So i was playing around with VertexFactory and SceneProxy to simply draw a Quad or Triangle. It works. Now i wanted to set an Array of Integers or Floats that is present for each vertex so i can pick the number i need from the Array. But i can't bind the Array to the Shader.

 FPlanetShaderParameters* FPlanetVertexFactory::ConstructShaderParameters(EShaderFrequency ShaderFrequency)
     if (ShaderFrequency == SF_Vertex)
         return new FPlanetShaderParameters();
     return nullptr;

 void FPlanetShaderParameters::Bind(const class FShaderParameterMap& ParameterMap)
     testValues.Bind(ParameterMap, TEXT("testValue"), SPF_Mandatory);
 void FPlanetShaderParameters::Serialize(FArchive& Ar)
     Ar << testValues;
 void FPlanetShaderParameters::SetMesh(FRHICommandList & RHICmdList, FShader * Shader, const FVertexFactory * VertexFactory, const FSceneView & View, const FMeshBatchElement & BatchElement, uint32 DataFlags) const
     FShaderParameterMap testMap;
     FRHIVertexShader* VS = Shader->GetVertexShader();
     TArray<float> testFloat;
     SetShaderValue(RHICmdList, VS, testValues, testFloat, 4);

Somehow Bind(...) never gets called. But SetMesh(...) does... I checked Implementations in the Engine Code and couldn't find a Solution

Product Version: UE 4.21
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asked May 20 '19 at 02:34 PM in C++ Programming

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avatar image HOUmmel May 20 '19 at 06:01 PM

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Let's discuss :

Yes, in the landscape module , FLandscapeVertexFactoryVertexShaderParameters::Bind is nerver called, you can ue_log to check that .but GetElementShaderBindings is called every frame and in that member method, you can see it's member parameters are actually bound.

I wonder why, maybe bind will be called only once and after being Serialized it will never be called?

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answered Jun 17 '19 at 01:12 PM

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avatar image knziha Jun 17 '19 at 01:38 PM

Okay I guess the serialized archive will act as a key and unless the key has changed the shaderparamters won's be re bound, is it the mechanism ?

avatar image HOUmmel Jun 17 '19 at 06:01 PM

Shader parameters are bound when you start the editor. i can't remember if this was the issue

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