[FRDGExternalBuffer](API\Runtime\Renderer\FRDGExternalBuffer) GetTangentBuffer ( class [FRDGBuilder](API\Runtime\RenderCore\FRDGBuilder) & GraphBuilder, class [FGlobalShaderMap](API\Runtime\RenderCore\FGlobalShaderMap) * ShaderMap, uint32 PointCount, uint32 CurveCount )