UE4 – Basic Material Blending

Software:
Unreal Engine 4.24

The example explained in this article is creating a blend between a mud material, and a mud-leaves material using a mask (Alpha) texture.
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The scanned PBR materials in demonstrated in this post are from Texture Haven (texturehaven.com)

How does it work?
There is actually no blending of Unreal materials, but rather a regular Unreal material in which each of the parameters is defined as a linear blend between 2 different source values for that parameter.
We could create such a material blueprint that uses a Lerp (Linear Interpolate) node’s to provide each of the material parameters with a blend of 2 input textures/colors or parameters, connecting the alpha texture to all the Lerp nodes’s Alpha input, and effectively achieve blending of 2 different materials, but it would be a complex blueprint in which it’s very inconvenient to design each of the individual materials participating in the blend:
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This complexity can be greatly simplified by collecting each of the participating materials parameters into a Material Attributes data structure.
The Material Attributes data structure contains all the data needed to compile a material, and allows input, output, and processing of this data as a single blueprint data stream (connection).
For example, when the material parameters are grouped as a Material Attributes data structure, they can be blended by connecting them into a single BlendMaterialAttributes node, instead of “Lerping” (blending) between 2 inputs to create each individual material parameter, which produces an unworkable complex material blueprint like the previous example.

> To collect material parameters into a Material Attributes data structure, connect them into a MakeMaterialAttributes node:
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> To create a blend between 2 Material Attributes data streams, use the BlendMaterialAttributes node:
* The Alpha parameter determines the weights of the blend (a black and white texture can be connected to it as the blend mask)
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> In order for the material output to receive a grouped Material attributes input instead of individual inputs for each parameter, select the material output, and in the Details panel, check the Use Material Attributes option:
matatts

Using the Material Attributes data structure, the blended material’s Blueprint in now much simpler and cleaner, while producing the exact same result as before:
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But designing 2 different materials within one material Blueprint is still far from being ideal..
What if we want to use just one of these materials on some surfaces?
What if the individual materials are not as simple as the materials shown here, it would be mush more efficient to be able to have one Blueprint for each of the materials allowing to focus on its development and preview it.
We can achieve this desired workflow by developing each of the materials as a Material Function.
Each of the participating materials is created as a Material Function with a Material Attributes output.

> One of the huge advantages of UE4’s material editing is that it allows us to preview a full material while developing it as a Material Function.
* This may sound trivial, but it isn’t. the Material Function isn’t compiled by itself as a material, it just produces data needed to define a material. in many other media production systems, this would have meant that you can develop data within the function but only preview it in the main material where the function is used.

> Learn how to create Material Functions

The Material Function defining the mud material:
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The Material Function defining the mud-leaves material:
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The Blend material using the Material Function nodes:
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Note:
When blending a non-metallic material with a metal material, the alpha values (mask colors) should be only 0 or 1 (black or white), otherwise blend areas that have a mid-range metallic value will make no sense visually.
> A RemapValueRange node can be used to force a color threshold on the mask texture or value.

Related:
Material Functions
Material Instances
Texture Painting

UE4 – Material Functions explanation and Example

Software:
Unreal Engine 4.24

Material Functions encapsulate shading flow graphs (material blueprints) into reusable shading nodes that have their own inputs and outputs.
This allows development of custom shading nodes, and saving the time it takes to recreate the same flow graphs multiple times or even copy and paste material flow graphs.
Common shading processes and operations that have to be performed in many different materials, and even multiple times in a single material can be defined as a Material Function for quick and easy re-usability.
Material functions can also be used to encapsulate a full material blueprint with a Material Attributes output. this provides a convenient workflow for blending different materials together.

In this post I’ll detail the steps needed to create and use a Material Function.
The Material Function example we’ll create, called “ColorAngleBlend” performs a commonly needed shading operation of blending 2 colors or textures according to the surface viewing angle (facing ratio).

The ColorAngleBlend Material Function will have the following inputs:

  1. color a:
    The color or texture appearing when viewing the surface at perpendicular angle.
  2. color b:
    The color or texture appearing when viewing the surface at grazing view angle.
  3. curve exponent:
    The steepness of the blend curve between the colors, 1 being a linear blend and higher values displaying color a at more angles “pushing” color b to be seen only at grazing angle.
  4. base color blend:
    The percent of color b seen at perpendicular view angle.
  5. normal:
    bump normals input.

The final “ColorAngleBlend” Material Function Blueprint:
* The internals of the “ColorAngleBlend” Material Function
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An example of the “ColorAngleBlend” Material Function node used to create a reach view-angle dependent color blend for a steampunk metal material:
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An example of the “ColorAngleBlend” Material Function node used to create a reach color for a car-paint material:
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An example of the “ColorAngleBlend” Material Function node used to create a washed-out effect for a cloth material:Annotation 2019-12-24 151927
Steps for creating the “ColorAngleBlend” Material Function:

  1. In the content browser, create a Material Function Object and name it “ColorAngleBlend”:
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  2. Double click the ColorAngleBlend Material Function to open it for editing:
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  3. Click the background of the work space to deselect the Output Result Node,
    So that the Details panel on the left will display the Material Functions‘s properties.
    Type a description into the Description field, check the Expose to Library option so that the new Material Function will be available to all materials in the Palate and node search, and define in which node categories it should appear:
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  4. Select the Output Result node and in the Details panel on the left set its output name to “color”:
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  5. Add a Linear Interpolate (Lerp) node, a Fresnel node and a Transform Vector (Tangent space to World space) node to the Blueprint and connect the nodes like this:
    * The Lerp node will blend the 2 color inputs with the Fresnel providing view angle data as the alpha for the Lerp.
    The Transform Vector  node is needed to convert normal (bump) input to world space for the Fresnel node.
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  6. Adding function inputs:
    Create 2 Function Input nodes, in their Details panel, name them “color a” and “color b”, leave their Input Type as default Vector3D, check the option Use Preview Value as Default, number their Sort Priority parameters 0 and 1 to make them appear as the first inputs of the ColorAngleBlend node as it will appear when used in a material, and connect them to the Lerp node’s A and B inputs:
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  7. Adding function inputs:
    Create 2 new Function Input nodes, name them “curve exponent” and “base color blend”, this time set their Input Type to Scalar, check the option Use Preview Value as Default, set their Sort Priority parameters to 2 and 3 and connect their outputs to the Fresnel node’s ExpoentIn and BaseReflectFractionIn inputs:
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  8. Adding function inputs:
    Create the final Function Input node, name it “normal“, set its Input Type to Vector3D, check its Preview Value as Default option, set its Sort Priority to 4, and connect its output to the Fresnel node’s Normal input:
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  9. Adding default inputs:
    Finally, add constant nodes to serve as default input values for the Material Function.
    A pure white Constant3Vector (color) constant as the default value for “color a” input,
    A pure black Constant3Vector (color) constant as the default value for “color a” input,
    A Constant with value 1.0 as the default value for “curve exponent” input,
    A Constant with value 0.0 as the default value for”base color blend” input,
    A pure blue Constant3Vector (color) constant as the default value for “normal” input.
    > Tip for quick creation of constant value nodes
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  10. Save the new Material Function.

To use the new ColorAngleBlend Material Function create a new material, in the node search start typing color… to locate the ColorAngleBlend node and create it, and connect it to the desired material input.

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> Material Functions can also be used by dragging them from the Content Browser into the Material Blueprint.

Related posts:
UE4 Material Instances
UE4 Fresnel node

Basic Cloth Material in Arnold for Maya

Software:
Maya 2018 | Arnold 5

An example of a basic traditional (not scanned) cloth material setup in Arnold 5 for Maya using an aiStandardSurface shader.

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The shading network uses a classic angle dependent color blend to simulate the color of the cloth being washed out at grazing angle of view.

Explanation of the node graph:

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  1. A black and white fabric weave texture that will serve as input for multiple shading channels.
    * This is actually not the best example of such a pattern, and could be replaced with a much better texture.
    cotton grey bump
  2. A remapValue node is used to set contrast to the fabric pattern (reduce contrast in this case) prior to it being multiplied with the fabric colors.
    * Note that only one of the textures RGB channels is connected to the remapValue node since it’s a float (mono) processor and not RGB.
    Untitled-3
    * Note that depending on the fabric texture, you may have to design different curves to achieve the right effect.
  3. Two colors are defined with colorConstant nodes:
    A deep color as the main fabric color, and a washed out color for grazing angle view (“side color”).
  4. An aiFacingRatio node is used as an input for incident angle info.
    * Note that in this case I checked the node’s invert option to make it behave more like other systems I’m used to (if you don’t use invert, the angle blend curve in 5 will be different..)
  5.  A remapValue node used to set the angle blend curve or in other words, how much does the color appears washed out per change of view angle of the cloth surface.
    * The longer it take the curve to become steep from left to right, the more the main color will be dominant before the washed out color will appear.
    Untitled-4
  6. A colorCorrect node is used in this example just as a way to convert the remapped float value back to RGB for being multiplied with the cloth colors.
    * We could also connect it directly to the individual float components of the RGB colors but this way the node graph is cleaner.
  7. A multiplyDivide node is used to multiply the processed fabric texture with the 2 fabric colors “baking” the pattern into the color.
  8. A blendColors node is used to blend the 2 processed fabric colors together according to the processed facingRatio angle input.
    The result is the final cloth color that is connected to the aiStandardSurface shader.
  9. An aiBump2d node is used to convert the fabric pattern to normal data that will be connected to the aiStandardSurface shader to produce bumps.
  10. An aiStandartSurface shader serving as the main shading node for this material.
    * Note that under Geometry the Thin Walled option is checked so that the Subsurface layer of the shader will act as a Paper Shader rather than SSS.
    * The main cloth color is connected to the SubSurface Color input.
    Untitled-5

 

More Arnold shading posts