The Uniqueness of Screen Space Reflections in HDRP — Unity3D

Screen Space Reflections (SSR) are a captivating visual effect in game development that add depth and realism to the virtual world. By simulating the reflection of objects in real-time, SSR enhances the overall visual fidelity and immersion for players. In this article, we will explore the uniqueness of SSR and delve into their inner workings, focusing on the components used within the High Definition Render Pipeline (HDRP) in Unity3D.

1. Understanding the Uniqueness of Screen Space Reflections: Screen Space Reflections offer a unique approach to rendering realistic reflections in real-time. Unlike traditional reflection techniques that rely on expensive ray tracing algorithms, SSR provides an efficient alternative that leverages the information available within the screen space.
2. How Screen Space Reflections Work: SSR starts by capturing the current frame’s color and depth information, along with other relevant data, such as surface normals. It then uses this information to calculate the reflected ray directions for each pixel on the screen. By tracing these rays, SSR determines what objects are visible in the reflected view and approximates the intensity and color of the reflections based on the surrounding scene.
3. Components of Screen Space Reflections in the High Definition Render Pipeline:

• Depth Buffer: The depth buffer is crucial for SSR, as it provides information about the distance of each pixel from the camera. This depth information helps determine the positions of objects and their occlusion in the reflected view.
• Normal Buffer: The normal buffer stores the surface normals of objects within the scene. These normals play a vital role in calculating the reflection vector for each pixel and ensuring accurate reflections based on the object’s geometry.
• Roughness Buffer: The roughness buffer provides information about the smoothness or roughness of surfaces. This data influences the intensity and clarity of reflections, allowing SSR to accurately simulate the behavior of different materials.
• Accumulation Buffer: The accumulation buffer stores the intermediate results of SSR calculations. It helps reduce flickering and improves the overall stability of the reflections over time.

Example Use Cases and Benefits of Screen Space Reflections:

a. Mirrors and Reflective Surfaces: SSR is ideal for rendering reflections on mirrors, shiny surfaces, or any object that requires real-time dynamic reflections. It allows for accurate representation of the surrounding environment, enhancing the sense of realism and immersion.

b. Water and Puddles: SSR is commonly used to create realistic water reflections in games. By applying SSR to water surfaces, developers can achieve convincing reflections that interact dynamically with the surrounding objects and the player’s actions.

c. Global Illumination: SSR can contribute to the overall global illumination in a scene by providing indirect lighting from reflected sources. This helps to improve the lighting consistency and realism, even in complex and dynamic environments.

To start enabling this great tool, first go to Project Settings > Quality (HDRP) > Lighting > Reflections:

Click on Enable.

Screen Space Reflections toggled on

Then inside the Global Volume add the Override for Screen Space Reflection and enable all, playing around with the parameters until scene looks good.

I also added two reflection probes of type real-time; reflections should now look pretty neat:

Two reflection probes showing the entrance of the room

roof and walls

Floor and walls

Screen Space Reflections are a unique visual effect in game development that adds depth and realism to virtual worlds. By leveraging the information available within the screen space, SSR provides real-time and efficient reflections. With the use of components such as depth buffer, normal buffer, roughness buffer, and accumulation buffer within the High Definition Render Pipeline, developers can achieve stunning and immersive visuals in Unity3D. Incorporating SSR in games opens up a wide range of possibilities, from realistic water reflections to dynamic mirror surfaces, contributing to the overall visual quality and player experience. It may be expensive for some GPUs to process such visuals, but going for a AAA quality scene has its price.