Decals: All you need to know
Decals are an essential part of modern gaming and real-time rendering. They are used to add surface details to models and enhance the realism of virtual environments. A decal is essentially an image that is projected onto a surface and can be used to create a variety of effects, including scratches, dirt, grime, bullet holes, and more. In this article, we will discuss decals in PBR (physically-based rendering) textures, which are becoming increasingly popular in the gaming industry.
PBR textures are designed to simulate the physical properties of real-world materials. They use a set of maps that define different properties of a material, such as color, roughness, metalness, and more. These maps are then combined to create a realistic material that responds realistically to lighting and environmental conditions.
Decals can be added to PBR textures to add additional surface detail that is not defined by the underlying material properties. For example, a decal of a bullet hole can be applied to a metal surface to create the impression that the surface has been damaged by a projectile.
The process of applying decals to a PBR texture is relatively straightforward. The first step is to create the decal image itself. This can be done using any image editing software, such as Photoshop or GIMP. The decal should be saved as a transparent PNG file to ensure that only the visible portions of the decal are applied to the surface.
Once the decal image has been created, it can be applied to the PBR texture using a process called “decal projection.” Decal projection involves projecting the decal image onto the surface of the model using a special shader. The shader uses the normal map of the surface to ensure that the decal conforms to the surface geometry, and can also be configured to adjust the opacity of the decal based on the angle of incidence of the incoming light.
One important consideration when using decals in PBR textures is the issue of texture resolution. Decals are typically added to textures as additional layers, which can significantly increase the overall size of the texture. This can be a problem for performance-critical applications, such as real-time rendering, where larger textures can lead to longer load times and reduced frame rates.
To address this issue, many game engines and rendering frameworks support a technique called “texture streaming.” Texture streaming involves dynamically loading and unloading texture data based on the user’s position in the virtual environment. This allows large textures to be used without impacting performance.
Another consideration when using decals in PBR textures is the issue of blending. Blending refers to the process of combining multiple textures or materials together to create a more complex surface. When adding a decal to a surface that already has multiple layers, it is important to ensure that the decal blends seamlessly with the underlying materials. This can be achieved using techniques such as alpha blending or masking.
In summary, decals are an essential tool for adding surface detail to PBR textures in modern gaming and real-time rendering applications. They allow developers to add a variety of effects to models and environments, enhancing the realism and immersion of the virtual world. While there are some challenges associated with using decals, such as texture resolution and blending, these issues can be addressed using techniques such as texture streaming and alpha blending. With the growing popularity of PBR textures and real-time rendering, decals are sure to remain an important part of the game developer’s toolkit for years to come.