Detailing the Scene with Decals

Decals in CGI are textures projected onto 3D models to add surface detail, such as logos, labels, or patterns. They remain independent objects from the surface they are projected onto and are commonly used in software including Blender, Maya, and Corona. To understand how they work, think of a spotlight projecting light onto surfaces that can be moved freely. Decals function similarly, projecting textures and colors onto multiple channels such as Base Color, Normal, and Roughness. In video games, a common application for decals is simulating effects such as blood splatters, where their characteristics differ from the underlying surface, making decals ideal for such tasks.

Decals in Unreal Engine offer a flexible and efficient way to add detailed visual elements to surfaces without the need for complex geometry or additional texture mapping.

In this chapter, we’re going to cover the following main topics:

• Fundamentals of what Decals...

Technical requirements

The project files for the chapter can be found at https://github.com/PacktPublishing/Architectural-Visualization-in-Unreal-Engine-5

Fundamentals of decals

In Unreal Engine, a decal is a 2D image that can be projected onto surfaces in a 3D scene to add details, such as signs, stains, or other visual elements. Decals are commonly used to enhance the realism and visual quality of a game or interactive experience and can be placed on any Static or Dynamic Mesh surface. When a decal is projected onto a surface, it blends with the underlying Material, creating the illusion of the image being “painted” onto the surface.

Here’s a simplified overview of how decals work in Unreal Engine:

1. Decal Material: To create a decal, you need a Decal Material, which is a special type of shader that includes transparency and can be applied to surfaces.
2. Applying the decal: You can easily apply a decal to a pre-existing Decal Actor. This Actor acts as a Volume, projecting the decal onto surfaces where they intersect. Alternatively, you may simply drag the Decal Material directly into the scene and a...

Types and a case study

Decals are incredibly versatile tools that can accomplish various tasks, simplifying what would have otherwise required more complex solutions. While I will focus on the main uses relevant to architectural visualization, it’s important to note that decals have many more applications in video games or interactive experiences, such as bullet holes, blood splatters, position indicators, and more. Here are some key applications of decals in Archviz:

• Imperfections, stains, and mold: Decals can be used to create realistic weathered looks, including leakages, dampness, dirt, and other imperfections that enhance believability. These decals can alter the Base Color and modify the Roughness of surfaces.
• Road markings, indications, and graffiti: Decals are ideal for adding painted elements such as road markings, signs, or graffiti. These decals can entirely replace the Base Color and Roughness of surfaces, and sometimes even have their own Normal map...

Project – creating your first decal

We are going to create a decal that will be useful for our project scene. Specifically, we want to create scratches and dirty markings for the wooden floor. These elements add undeniable realism to the scene. By using a decal to do this, we gain great flexibility in terms of positioning and avoid the need to create a super complex Material with masks, which would inevitably end up being repetitive. Follow these steps:

1. To begin, right-click inside the Content Browser and create a new master Material named D_scratches. Open the Material editor and select the main Material node. Change Domain to Deferred Decal and Blend Mode to Translucent.
2. In our case, the scratches will mainly alter the Normal and Roughness values, not the Base Color (although they might in other cases). To achieve this, we use the same expression we used for Normals in the PBR Material, and we plug a simple scalarParameter for Roughness, setting it to a high value...

Summary

In this chapter, we covered a fundamental aspect of CGI, which is the use of decals to enhance and define scenes effortlessly. We learned how to quickly create and utilize decals, exploring their various applications. Additionally, we delved into a specific type of decal, the Mesh Decal, and acquired the knowledge to create and implement it effectively.

With this chapter, we have completed an essential part of this book. We now possess the skills to create a complete architectural scene, encompassing models, lighting, Materials, and decals. In the upcoming chapter, we will delve into an entirely different topic that makes Unreal Engine so immensely powerful—the Blueprint system. This system serves as the foundation upon which Unreal Engine operates and is integral to its functionality.