Creation of Parallax Occlusion Mapping (POM) in details

Creation of Parallax Occlusion Mapping (POM) in details

It’s still a problem understanding such a complex approach in materials like POM and we’ll try to deeply understand how to use POM and as short as possible. Also we’re going to explain what each node does and why we use each one of them.

Let’s start with what materials are in Unreal Engine? Materials in Unreal Engine define the surface properties of the objects in your scene. A material is something like a "paint" that defines the visual appearance of an object.

Now what is POM? Parallax Occlusion Mapping (POM) is a complex texture-based approach to add more details for meshes. With POM we get more depth visually than we could get just with Normal maps, because we get three-dimensional shapes without adding any additional vertices to meshes. POM uses Ray Tracing to find the correct offsets at each point.

So why is Parallax Occlusion better than making subdivision to meshes?

But there are also some things that you should remember:

So let’s create a POM material. First, let’s create a material. Press the right mouse button in “Content browser” and pick “Material”, now you should name it. Since it will be a master material, let’s name it M_POMbricks or MM_POMbricks. The difference between “Master Material” and “Material Instance” is like a parent to a child in programming. If a parent has some values a child will get them too, but a change of values of a child won’t affect a parent. The connection between them is called a “Parameter”.

We’ve got now a completely clean material and we need textures. We can make our own textures, but our main subject is POM , so let’s press the right mouse button on “Content Browser” and pick “Add Quixel Content”. Find a brick material. In my case it’s “BRICK WALL”. Download it.

After downloading it, open the material that we created before by pressing the left mouse button twice. To have these textures, you have to select the textures of “BRICK WALL” and move it to the Material Graph. Then you should connect them all like in the screenshot below.

The texture with usual colors without any information about light (Albedo) belongs to “Base color”, it gives colors that we need to see in a brick wall in this case. The blue texture belongs to “Normal”, because it gives depth. But the yellow texture that we call “ARD” texture differs from others, because it has a few textures inside in different channels, so we’re going to use some of them. ARD = Ambient occlusion + Roughness + Displacement, that’s why we connected like what’s on the screenshot.

Now let’s create more nodes so we could finally have a POM effect. To create a node press the right mouse button inside of the material graph and write the name of your node. Or press the palette and find the nodes that you need. In the screenshot there are names for each node.

Constant - is a number that we’re going to need to give a numerical value. It’s a little green node. Press the right mouse button and type “Constant”, then press the left mouse button on it. Names of other nodes you can see in screenshots below.

Let’s continue. You see that constante nodes have different names in the screenshots? It’s because they’re not just nodes, they’re Parameters. Now you have to press the right mouse button on them and press “Convert to Parameter”, then you name them like in these screenshots.

Now let’s explore each node. What does each of them mean?

1)Channel (it’s called so because we named it like that after making this node a Parameter) - is a four-vector constant, to create it you need to write not just “constant”, but “constant4vector”. As we wrote before, this node controls which channel is going to be provided to ParallaxOcclusionMapping. If you remember what we wrote about ARD, then you can guess that we’re going to use “B” channel, which means we have to make it completely Blue, so it should be 0,0,1,0. Also we used the node “Append”, because ParallaxOcclusionMapping expects us to give value of constant4vector (that’s why there’s written V4) and since four-vectors constantes have Alpha channel we give the color (B channel) and alpha.

2)Texture Coordinate controls scaling of the texture. Create another node and connect it to “Multiply” (this node multiplies two connected values), create another node and connect it too. Now you can scale it. We need texture coordinates and the scale depends on the scene you’re creating.

3)Height Ratio (Parameter of one-vector constant) - controls values of our height map, in other words controls how much POM this material will be. We will write 0.3 as a default value and we’re going to change it in a material instance that we’re going to create, because everything depends on the textures that we use.

4)Min Steps and Max Steps - Values for making POM smooth. The more steps we have, the more smooth it becomes, it’s like the modifier “Subdivision” in Blender.

As you see we connected ParallaxOcclusionMapping to the textures, but we also connected “Pixel Depth Offset” of both nodes. We did it because otherwise we won’t have any POM effect. But again as I mentioned before, since we use Pixel Depth Offset, most likely you should turn off “Cast shadow” on actors on which we’re going to use our materials since they don’t work together very well.

We now understand why we created such nodes for the POM effect. Keep in mind that Material Instances with Parameters help us in making materials and this case shouldn’t be an exception either.

In the end of this article it would be great to add a few more things that could help you:

Written by Alexander Mukhitdinov, game developer of Skyhell, mentor and co-founder of Cube of Skill. Date - 26th August, 2024. Uzbekistan. cubeofskill@gmail.com