CGI image header of a graffiti of a girl on a wall

UE Materials and Decals

Jan 2024 Tutorials Unreal Engine

Unreal Engine is the leading software for real-time 3D production, used in games, film, TV, and simulations. It offers exciting opportunities for Indie Production companies, artists, and enthusiasts to turn their creative storylines into reality.

In this tutorial, we will guide you through the process of creating a graffiti decal to be used in a 3D game-ready level. We will start by gathering references, brainstorming ideas, creating concept art, and selecting one for the final production. Then, we will export the textures and set up the alpha channel in Photopea to use it in our 3D scene within Unreal Engine. All the software we’ll be using in this tutorial is available for free online.

So lets get started.

Before we start, let’s make sure you have all the necessary tools. You can find information and downloads for the required software in the Tech | Tools and Software section, or simply click here.

Reference gathering and Brainstorming.

The next step is optional but can be really helpful. If you haven’t heard of PureRef, it is an excellent tool for gathering references and brainstorming ideas. Take a few minutes to find some graffiti images you like on the web. A quick search on your preferred search engine should suffice. If you decide to use PureRef, it will save you a lot of time, as you can drag and drop or copy and paste any image you want directly into the app, without having to download or save them individually.

In the image above, you can see some of the references I have chosen. I am thinking of creating graffiti that includes a character and making it all work together. However, since this tutorial is just about creating a decal, I won’t go into too much detail about the narrative, or how graffiti and decals can be used to guide a player through a game. Keep in mind that colors and textures are important details that should suit the overall look and feel of your scene.

Concepts and Final design.

This is the fun part where you get to unleash your creativity by sketching out your wildest ideas. Take your time to experiment with different fonts, angles, colors, and sizes to come up with the best design. Also, play around with character design, poses, and style to bring your ideas to life.

On a slightly different note, you can use AI synthography and software like Stable Diffusion to quickly create different designs and refine them as you build your final design. By using descriptive prompts of what you’re trying to achieve, you can come up with almost-ready colored concepts and make any necessary changes in software like Photopea.

Make sure you set up your file to export at the correct resolution and map size to avoid any scaling issues in the future. Texture maps are essential for the final appearance of 3D models, providing color, detail, and texture to surfaces. Choosing the right size for your texture maps is crucial, as it can significantly impact the overall quality of your 3D characters.

For film use, texture maps should be high-resolution, with a map size of 8k (7680×320) being the best option to ensure they look sharp and have lots of detail, even in close-ups. For gaming, texture maps should be optimized for real-time rendering, with a 2k (2048 x 1080) or lower being the best option depending on the platform.

Most graphics hardware requires texture images to be a size that is a power of two in each dimension. This means you can use any of the following options for a texture size: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, and so on. However, unless you have a high-end graphics card, you’ll probably need to stop at 2048.

The textures don’t necessarily have to be square, but each dimension usually has to be a power of two. So, 64×128, 512×32, or 256×256 are acceptable, but 200×200 is not allowed because 200 isn’t a power of two. For more detailed information about map size and resolution, click here.

ResolutionMeasurements(pxls)Pixel Count
8K Ultra HD7680 x 432033,177,600
4K Ultra HD3840 x 21608,294,400
1080p Full HD1920 x 10802,073,600
720p HD1280 x 720921,600
480p SD640 x 480307,000
For detailed information about map size and resolutions, click here

Alpha channels and Exporting

Alpha channels are essential for images that require transparencies. They consist of red, green, and blue channels that determine how a pixel is rendered when blended with others. These channels allow for images to be composited together without altering their transparency.

After creating several concepts, we have finalized our image. The next step is to ensure that it has the correct output size and resolution. We will then add a mask to the image and introduce scratches, wear and tear, and water damage to make it look more realistic.

To achieve this, we have created two layers: a background layer and our final image layer. The background layer is an aged old wall that will serve as a guide for the final look of the image once it is imported into UE and placed on a similar-looking 3D model of a wall. The final image layer will have a mask applied to it. By adjusting the brush size, brush types, and different shades of black to grey, we will add weathering to the final image. We will start with a small opacity level and work our way outwards, increasing the opacity level to increase the transparency levels on the outside of the image.

Once we are satisfied with the details added to the image, we will proceed to adjust the Alpha channels to ensure that all the details are preserved when the final image is transferred into UE. To create the alpha channel, we will select the mask with the image layer and switch to the Channels tab to view the RGB channels. We will then create the alpha channel by clicking on the ‘Create a new channel’ button. Once created, we will deselect the mask and click through all the channels to see each channel independently and what the alpha is displaying.

Finally, we will save our image in the correct format for export to UE. We will choose the TARGA (TGA) file format, which supports 32-bit true color and is typically used as a true color format. Targa files are widely used to render still images and sequences of still images to videotape.

Using Materials and Decals

Alright, we’re now in UE and ready to complete the final steps of our tutorial. To begin, create a new project in UE. I suggest creating a Video & Film project as this is a simple decal and graffiti tutorial, but you can choose any project type depending on your needs.

Once you’re inside the UE interface and can see your viewport window, create a cube and adjust it to look like a wall. Proceed to the open bridge within UE and select a surface material that looks like a wall or any other material you desire to use as your background. I chose a Dirty Concrete Wall from within the Surface and Concrete section in the Bridge and adjusted the settings within the wall material to give it a more realistic look. I kept the floor as it was to focus all the attention on the wall and the new material decal graffiti.

Now that we have our wall, let’s create some graffiti. First, open our Content Browser within UE, create a new folder called Materials, and open it. Inside this folder, create a new Material named “TM_GraffitiDecal_Master_01a”. I suggest using the same naming convention throughout your project to keep things organized and find items easily.

Once you’ve created your material, open it and ensure that you change some settings first. Every newly created material defaults to a material domain of Surface, but we want to change this to Differed Decal. Under it, we’ll change its blending mode to translucent.

Next, import the image texture we created earlier. To do so, open your Content Browser, create a new folder labeled Decals inside the Content folder, and open it. Import your image into the newly created folder, open it up, and ensure that all your channels were imported correctly.

Now, go back to your newly created material, and drag and drop the image texture into the Materials Graph Window. Once you’ve dropped the texture image inside the material graph, drag and connect the RGB socket to the Base Color node. Do the same for the A (alpha) socket and connect it to the opacity socket. After this, you can proceed to the main Viewport, drag and drop the newly created material into the project, and place it on the wall. If it doesn’t look right, try changing its rotation, scale, and location until it looks perfect.

Congratulations, you have now created your first graffiti in UE! You can further add more details to this by adjusting the details within the texture material and the material options. You can also use these same steps to bring decals, posters, pictures, images, and many other items your imagination can come up with to make your scene look more realistic.

I hope you enjoyed this tutorial and learned something new. Please leave a comment, like, follow us, or subscribe to win a free t-shirt and stay up to date when new tutorials come out, promotions, and stay informed of what’s happening in the world of venezArt Dev Studio.

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