Developing Artistic Ice in Unreal Engine 4
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Developing Artistic Ice in Unreal Engine 4
16 May, 2017
Interview

Taizyd Korambayil gave a detailed description of his approach to the creation of the ice shader creation and shared some tips for technical artists. This is some of the most amazing examples of ice shader we’ve ever seen. 

If you are interested in the production of this shader, you can download the whole thing here. You can download the texture and shader files for free.

Introduction

Hi, my name is Taizyd Korambayil, I graduated from the Savannah College of Art and Design in 2015 with a BFA in Game Development. After graduation, I went to work at Epic Games in Cary, NC. I worked there between 2015-2017.I worked in the Engine Content Team at Epic, I was basically in-charge of updating and bug fixing all the template/sample projects available with the engine. During my time there I also got to work on paragon a little, mostly just minor work with bug fixing art content in the map. I think it was my junior year in college that I really began delving into the field of Technical Art, seeing all the cool things people were doing with shaders inspired me to want to pursue this path, and I’ve been learning ever since.I am currently back in school for a Master’s Degree. 

UE4’s Material Editor 

UE4’s Material Editor can be used to achieve almost anything you want, there is of course the odd occassion where you need to bust out the “Custom” node and use some HLSL but for the most part it’s enough. Substance Designer is more like a procedural photoshop, I don’t think you can really compare the two as they serve quite different purposes, but I do use both a lot. I usually generate any patterns I need for my shaders in substance and bring them into UE4.

References

When I first started working on this material my only thought was Ice, but I quickly realized that there are many different kinds of ice I could make, frozen rocks,ice cubes, frozen lake surface, a frozen object and each of them have different unique characteristics. My goal was to create a general purpose ice shader, something that had adjustable parameters and could be decently interchanged for any kind of use. I looked at a lot of reference images of frozen lakes, lots of pictures of the arctic, Images of Ice caves were a huge inspiration when I worked on this. The goal of the project was to get a better understanding of material look-dev inside unreal. 

Colors

I decided to go with an Analogous Color palette of deep and light blues, I used Adobe’s Kuler to pick a color Palette. So, the way the colors are combined is using masks, I basically take the Pattern textures and perform some operations on them in the material editor to create some variation as well as well as add some depth effects, then I use them to Interpolate between colors. The end result of colors is depend on a lot of factors, like opacity, subsurface and viewing angle etc. I think the colors at the moment may be a little too saturated but all of these are parameterized so that an artist can tweak it to their desire. 

Patterns

I had initially gone with a more cloudy pattern, but I got some feedback about how it looked more like jello than ice. So I had to go back and re-think the patterns I used, and that’s when I noticed the crack patterns on Frozen lake surfaces. When I went back to my reference images, this was a common pattern that I saw, so it made sense to try and make crack pattern like this. The crack pattern is actually used multiple times in the shader, its used to mask bubbles, it’s used control the roughness in specific areas, and it’s also got an offset version layered underneath to fake subsurface cracks.

Lighting

Lighting is definitely very important, especially with materials like this which use subsurface and translucent elements. Lighting is especially important to get some nice looking subsurface, In my screenshots, I’ve used Epic’s Lightstage map, which by default has good lighting for showcasing assets, but I tweaked it a little to suit my needs, I set up a basic 3-point lighting system with a strong rim/backlight to show the subsurface and added a little bit of color grading to add a cooler atmosphere. 

Depth

The fake “depth” was definitely one of my biggest goals with this project, I really wanted to capture that effect in the material. In unreal there is a node called “BumpOffset” which lets you add parallax to your textures. The process to achieve the end result was basically a layering of textures with different parallax values and then bringing them all together for the final effect. If you refer to my breakdown this is explained fully.

Ice Material Breakdown

So I’ve been meaning to do this for a while, but unfortunately finding time was tricky, but I’ve managed to sneak in some free time in-between assignments to make this write-up. Now, Full disclosure, I am no pro, this was a result of me researching/experimenting trying to get a result, lots of googling etc. So it may not be perfect, feel free to leave some feedback or any changes you may suggest. Anyway lets get started.

Material Preview

Here is a preview of what the material looks like along with the entire material graph, if you’d rather not read through all my ramblings/explanation

My goal with this project was to create a “Genereal Purpose” ice material. Something that could be tweaked with parameters to work decently for any kind of use.

Textures

This material makes use of 4-5 textures depending on whether you choose to add a baked normal map for a mesh, 3 of them will contain patterns in each channel and one will be a general purpose noisy normal map. I used Substance Designer to generate these patterns and I thin I also found one or two wit on gogle. The images below show you how the textures are set up.

BubbleMask.tga

ColorMask-Crack-Roughness.tga

Subsurface-Height-Speckle.tga

NormalMap

BumpOffset Node:

This node in the UE4 Material Editor, basically helps us make use of parallax mapping, this is waht we use to fake the “depth” in this material. The basic explanation of how it works is this, you feed it a Coordinate value, a height value and a height ratio value. The Height Value determines the base or plane from which your height ratio is measured, so if you feed a height value 0 with a height ratio value of -1.0, pixels will appear as though they are “under” the surface, where as if you have a height value of 0 and a height ratio value of 1.0, pixels will appear to bulge above the surface (This can look very bad unless you use subtle values). Here’s the documentation page for the node:https://docs.unrealengine.com /latest/INT/Engine/Rendering/Materials/HowTo/BumpOffset/

Creating Masks for Surface Coloration

In this step, we are going to mix and match some of the textures we made to create some masks that we will use to control the shader’s coloration and expose some useful variables as parameters so that we can use it to tweak the shader’s appearance with Instances. You can see the network below:

First we create a scalar parameter, “Master Tiling”, we will use this to control the global tiling value for the entire material.

1: Next we create the basic setup that will repeat for all the textures that we use in the shader, we set up a scalar parameter to control the tiling for each TextureSample and multiply it by the Global Tiling parameter , we also setup the bumpOffset Node and the values for it’s inputs to be use.

We do some basic value adjustments to each texture sample with a power node, we do this to create some variation in the masks as we will be re-using the same textures many times in the shader. WIth this network set up we have 3 mask outputs ready to be used (labeled in the image). We will make use of these later.

Bubble,Cracks,Surface Masks

This part of the graph creates surface masks to control areas where the bubbles are visible.

In this section we are going to set up the the masks for the bubbles and surface cracks, see the node Graph below:

In the graph above we repeat the process of setting up tiling parameters for the textures for each texture sample.

1) This will be the upper most layer of bubbles,we will sue the Blue Channel of the texture as that is where we stored the blobby bubble pattern. We set a height ratio value of -0.2, so the bubbles appear just below the surface.

2) This section will be bubbles that are deeper inside the surface. First we set up two scalar parameters and add it to the texture coordinate, this will let us add some offsets in the U and V directions to create some variation. Next we repeat the procedure for setting up tiling values,We set a higher tiling value to make the bubbles appear smaller, to help improve the fake depth effect, In the Bump offset node we set a heihgt ratio of -1.0.

We multiply the end result of this network with the an the inverted result of Mask_01 from the previous section. This is done so the bubbles are not visible if they are under the Opaque sections of the ice surface. The gif below shows what the result of this network looks like.

Material Roughness

This section of the graph deals with how we set up the roughness input for the material, we do the same process as before and set up the tiling properties for the texture with the speckle pattern in the Blue channel, we use this as the mask to Lerp between a min an max roughness value. We expose these values as parameters so they can be tweaked. Finally we do a final lerp with the crack pattern mask from Mask_01, this is to give the cracked areas a different roughness than the rest of the surface.

This will serve as the roughness output for the material, if we preview it, it will look something like this:

Opacity/Subsurface Masking

Part 1:

In the following sections we will set up the Opacity output for the material, this part of the graph affect the material in two ways.

1.) It controls teh amount of subsurface scattering that occurs on the surfae of the mesh

2.) With translucency enabled,it controls how opaque/Translucent the material is.

So, this will affect how the Opacity output is used depending on whether we enable translucency or not

(Note: The translucent version of the material is quite expensive, use carefully, ideally any objects that use this shader should mip out to a cheaper version of the material quickly)

It is important to note that Opacity serves two purposes in this material, since our material uses a subsurface shading model, the opacity controls how much subsurface scattering happens on the surface of the object, in the opacity map, white areas = more scattering black areas= less scattering.

With translucency on the other hand, white areas = opaque, black areas = completely transparent. We need to keep this in mind as we build the opacity graph, so that we adress both these needs correctly

This first section just makes a basic mask using the texture we created earlier, but we also add some fresnel, so that the edges of the object do not become completely transparent as this can make the object feel floaty, and not very grounded in the world.

If you preview the node commented as opacity, you’ll see something like this:

Part 2: Camera Distance Mask

Here we set up a camera distance based mask, so that the translucency becomes visible only when we are closer than a specified distance from the object (in thi s case 512 units). This was a personal choice for me, I didn’t like the way objects looked translucent from afar and wanted it to happend only when the viewer was close to the object.

Here’s a gif showing what this network does, As you can see, the mask gets darker(i.e more transparent) the closer the camera is to the object.

Final Opacity Mask Blending

In this part we bring together all the previous masks we made and blend them together to get the final output that goes into the Opacity Input of the material:

If you preview the output of all these blends, it will look something like this.

BaseColor Pass

The section below shows how we combine all the masks we have created in the previous sections to make the basecolor pass for the material. I used Adobe’ Kuler to pick an Analogous Color palette of light and deep blues, we expose all these colors as Texture Parameters so that it can be tweaked to any artists desires. I’ve commented which Mask goes to which lerp node.

In the end we run everything through a Fuzzy shading Material Function, it works very similar to a fresnel but we are able to control the core darkness and the edge brightness, this function was commonly used when creating moss, cloth(before the release of the new shading model) and grass materials, but it provides an effect that I think works well with Ice as well.

If you preview the fuzzy shading node you will see something that looks like this. The output from this FuzzyShading Node will go into the BaseColor input of the material. This result will also be used to create the subsurface color in the next section.

Subsurface Color

The subsurface color output is generated by multiplying the Final Color Output with a parameterized color hue, and scaling factor to control how bright the color is. the output of this multiply node will go into the materials subsurface color input.

Normal Map

For the materials normal, the setup is simple, we use the normal texture, with uv coordinates from the Surface Masks section, we also add a static switch parameter to control whether we want to combine it with a baked object normal map. This option is made so that when we apply this material to an object with baked normal maps, we blend the ice normals with the objects baked normal map.

Performance, optimization/Final Thoughts

When you create an instance of this material, you will have the option, of using it as a either a translucent-Subsurface material or as an opaque subsurface material. Using the translucency is quite expensice and ideally you’d want to mip to a cheaper material pretty quickly. The opaque-subsurface version on the other hand is not as beefy and is quite performant.

If you look at the shader complexity comparison between a transparent-subsurface and an Opaque-subsurface version of the material you will there is quite a big difference. For proper estimation of performance of course you want to use the GPU profiler to get accurate information on exactly what is going on in the scene.

The image below shows all the parameters that are exposed to the material instance, these settings can be tweaked to achieve different looks with the same material.

Thank you for reading and I hope you find this useful!Cheers!

Taizyd Korambayil, Technical Artist

Interview conducted by Kirill Tokarev

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11 Comments on "Developing Artistic Ice in Unreal Engine 4"

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Ryan
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Ryan

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hope this img file works just copy in url bar I guess

Ryan
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Ryan
Shader looks great, tho the normal on the top seems almost invisible. I really like this tho, I think I can use something similar for a jade statue. But I do think on top of this having a few pieces of geo inside your ice to create the look of cracks that light up at the right viewing angle would be a great touch. 1 last thing and this is more nit picky then anything id say the layer of cracks that seems to be a copy of the top layer beneath maybe just for that layer use your fernsel… Read more »
ZeratuJiang
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ZeratuJiang

Amazing Work! It looks awesome!

Richard
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Richard

Awesome work dude. As a UE4 Tech Artist and Dev myself, I find this really inspiring and it makes me want to spend even more time playing around with textures and materials in Unreal Engine 4 rather than their blueprint system. I’m still kinda new to Substance Designer so I was wondering how did you create the Red, Green, Blue and Packed Texture in Substance Designer? Any info is appreciated 🙂 Keep up the awesome work.

taizyd@korambayil.com
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taizyd@korambayil.com

Sorry for the delayed reply @Scott, I didn’t think to look at the comments section, you can find the files here https://drive.google.com/open?id=0B3InlP3HbKL9YzdNTjVNOWlwRWs

Scott
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Scott

I just finished my PhD in Computer Vision, where my focus was on polar research applications. I’ve spent years 3D reconstructing ice and I really nerd out over ice in games and movies. This looks awesome and I would love to look at these models and materials in VR. Any chance you could put up a download link so we don’t have to recreate it ourselves? Or post it on the asset store?

Tayler
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Tayler

Thank you for sharing! A few questions. What Shading Model did you use? and What Translucency/lighting Mode?

Tayler
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Tayler

Edit* NM I see you listed that info

Katten
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Katten

good job!

Dingus
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Dingus

Looks really really nice! But holy moly, judging from that material graph, it would be impractical to use in game, performance-wise at least. Great job nonetheless.

Alberto D\'Aleo
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Alberto D\'Aleo

That is an awesome job. Congratulations.

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