Working with Material in Unreal Engine

Create Material Graph with C++

Creating Material Graph with C++ instead of using Blueprint nodes make sense especially to automate processes when working with a lot of materials. C++ is a way to move material data exported from any tool to the Unreal Engine and re-create them aitomatically to materials directly by code.

C++ comes it handy as well anytime there's a need to add a functionality that is not available through the common BP nodes.

• All Material extensions
• #include "MaterialEditingLibrary.h" // MaterialEditor (Editor Only) is required for working with Materials in C++ in the editor

All the code below is placed in UBlueprintFunctionLibrary inherited class.

• Build Material

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Build a material graph with the provided values
   *
   * @param MaterialPath	The path of the material: "/Game/Folder/MyMaterial"
   * @param TexturePath	The path of the texture to add in the material: "/Game/Folder/MyTexture"
   * @param TexCoord	Texture coordinates for the texture
   * @param Color	Color that will be multiplied by the texture
   * @param Metallic	Metallic value of the material
   * @param Specular	Specular value of the material
   * @param Roughness	Roughness value of the material
   * @param OutInfoMsg	More information about the action's result
   * 
   * @return If the action was a success or not
   */
  UFUNCTION(BlueprintCallable, Category = "")
  static bool BuildMaterial(FString MaterialPath, FString TexturePath, FVector2D TexCoord, FLinearColor Color, float Metallic, float Specular, float Roughness, FString& OutInfoMsg);

  .cpp

  .Build.cs

• Add TextureParameter node to Material

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Add a texture parameter to a material graph
   *
   * @param Material	The material in which to add the expression
   * @param Texture	The texture to use
   * @param ParameterName	The name of the expression
   * @param NodePos	The XY coordinates of the node in the graph
   *
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = "")
  static class UMaterialExpressionTextureSampleParameter2D* AddTextureParameter(UMaterial* Material, UTexture* Texture, FString ParameterName, FIntPoint NodePos);

  .cpp

• Add ScalarParameter node to Material

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Add a scalar parameter to a material graph
   *
   * @param Material	The material in which to add the expression
   * @param Value	The float value to use
   * @param ParameterName	The name of the expression
   * @param NodePos	The XY coordinates of the node in the graph
   *
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = " ")
  static class UMaterialExpressionScalarParameter* AddScalarParameter(UMaterial* Material, float Value, FString ParameterName, FIntPoint NodePos);

  .cpp

• Add VectorParameter node to Material

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Add a vector parameter to a material graph
   *
   * @param Material	The material in which to add the expression
   * @param Color	The color value to use
   * @param ParameterName	The name of the expression
   * @param NodePos	The XY coordinates of the node in the graph
   *
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = "<a href="https://www.youtube.com/watch?v=Fd56hSN83mk" target="_blank">Alex Quevillon|10 - Build Material</a>")
  static class UMaterialExpressionVectorParameter* AddVectorParameter(UMaterial* Material, FLinearColor Color, FString ParameterName, FIntPoint NodePos);

  .cpp

• Add MultiplyExpression node to Material

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Add a multiply expression to a material graph
   *
   * @param Material	The material in which to add the expression
   * @param ExpressionDesc	The description of the expression
   * @param NodePos	The XY coordinates of the node in the graph
   *
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = " ")
  static class UMaterialExpressionMultiply* AddMultiplyExpression(UMaterial* Material, FString ExpressionDesc, FIntPoint NodePos);

  .cpp

• Add TexCoordExpression node to Material

  .h

  	/**
   * Editor Only - Will not work in packaged build.
   *
   * Add a texture coordinate expression to a material graph
   *
   * @param Material	The material in which to add the expression
   * @param Value	The texture coordinates value to use
   * @param ExpressionDesc	The description of the expression
   * @param NodePos	The XY coordinates of the node in the graph
   *
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = "<a href="https://www.youtube.com/watch?v=Fd56hSN83mk" target="_blank">Alex Quevillon|10 - Build Material</a>")
  static class UMaterialExpressionTextureCoordinate* AddTexCoordExpression(UMaterial* Material, FVector2D Value, FString ExpressionDesc, FIntPoint NodePos);

  .cpp

• GetExistingMaterialExpressionFromName helpe function

  .h

  /**
   * Editor Only - Will not work in packaged build.
   *
   * Retrieve an existing material expression based on the provided name or description
   *
   * @param Material	The material in which the expression is
   * @param NameOrDescription	The name or description of the expression to find
   * 
   * @return The expression
   */
  UFUNCTION(BlueprintCallable, Category = " ")
  static class UMaterialExpression* GetExistingMaterialExpressionFromName(UMaterial* Material, FString NameOrDescription);

  .cpp

Assign Material to Mesh in C++

The code below allow to assign a material to Static Mesh as well as to Skeletal Mesh.

/**
 * Editor Only - Will not work in packaged build.
 *
 * Assign material to a mesh asset (static mesh or skeletal mesh)
 *
 * @param MeshPath	Path of the mesh: "/Game/Folder/MyMesh"
 * @param MaterialPath	Path of the material: "/Game/Folder/MyMaterial"
 * @param MaterialId	Material slot to assign material into
 * @param OutInfoMsg	More information about the action's result
 *
 * @return If the action was a success or not
 */
UFUNCTION(BlueprintCallable, Category = "<a href="https://www.youtube.com/watch?v=u3QOZUNeJOE" target="_blank">Alex Quevillon | Assign Material To Mesh</a>")
static bool AssignMaterialToMeshAsset(FString MeshPath, FString MaterialPath, int MaterialId, FString& OutInfoMsg);

#include "Engine/StaticMesh.h" // Engine
#include "Engine/SkeletalMesh.h" // Engine

bool UExampleClass::AssignMaterialToMeshAsset(FString MeshPath, FString MaterialPath, int MaterialId, FString& OutInfoMsg)
{
  // Load material
  UMaterialInterface* Material = Cast<UMaterialInterface>(StaticLoadObject(UObject::StaticClass(), nullptr, *MaterialPath));
  // Load mesh
  UObject* PotentialMesh = StaticLoadObject(UObject::StaticClass(), nullptr, *MeshPath);
  UStaticMesh* StaticMesh = Cast&lt;<a href="/unreal-engine/static-mesh">UStaticMesh</a>&gt;(PotentialMesh);
  USkeletalMesh* SkeletalMesh = Cast&lt;<a href="/unreal-engine/skeletal-mesh">USkeletalMesh</a>&gt;(PotentialMesh);

  if (StaticMesh != nullptr)
  {
    // <mark>Apply material to static mesh</mark>
    int RealMaterialId = FMath::Clamp(MaterialId, 0, StaticMesh-&gt;GetStaticMaterials().Num() - 1);
    StaticMesh-&gt;SetMaterial(RealMaterialId, Material);
    StaticMesh-&gt;PostEditChange();
  }
  else if (SkeletalMesh != nullptr)
  {
    // <mark>Apply material to skeletal mesh</mark>
    int RealMaterialId = FMath::Clamp(MaterialId, 0, SkeletalMesh-&gt;GetMaterials().Num() - 1);
    SkeletalMesh-&gt;GetMaterials()[RealMaterialId] = Material;
    SkeletalMesh-&gt;PostEditChange();
  }
  else
  {
    OutInfoMsg = FString::Printf(TEXT("Assign Material To Mesh Asset Failed - Mesh isn't valid. '%s'"), *MeshPath);
    return false;
  }

  OutInfoMsg = FString::Printf(TEXT("Assign Material To Mesh Asset Succeeded - '%s'"), *MeshPath);
  <strong>return true;</strong>
}