static bool ExportLandscapeMaterial ( const [ALandscapeProxy](API\Runtime\Landscape\ALandscapeProxy) * InLandscape, const [TSet](API\Runtime\Core\Containers\TSet)< [FPrimitiveComponentId](API\Runtime\Engine\FPrimitiveComponentId) > & HiddenPrimitives, [FFlattenMaterial](API\Developer\MaterialUtilities\FFlattenMaterial) & OutFlattenMaterial )