In this lesson, you will learn how to implement and fine-tune Screen Space Reflections (SSR) to add dynamic, environment-aware reflections to your reflective surfaces.
Understanding Screen Space Reflections
Screen Space Reflections work by tracing rays from your camera’s perspective across the depth buffer to find what is currently visible on the screen. Unlike static reflection probes, which capture the environment from a fixed point, SSR calculates reflections based on what the camera actually sees in real-time. This creates a powerful sense of grounded realism for polished floors, wet pavements, or metallic surfaces.
Implementing and Tuning
To enable SSR in the High Definition Render Pipeline (HDRP), you must first ensure your HDRP Asset has "Screen Space Reflection" enabled in the Rendering settings. Once enabled, you control the fidelity via a Screen Space Reflection Override in your Volume component.
The most critical parameters to tune for high-quality visuals are:
- Max Ray Steps: Determines how many "jumps" the ray takes across the screen. Higher values (e.g., 64–128) increase accuracy but hit performance harder.
- Ray Length: Limits how far the reflection can reach. Keep this tight to prevent "ghosting" artifacts where objects reflect things that aren't logically nearby.
- Denoising: Since SSR is a sampled effect, it can appear noisy. Utilizing temporal denoising helps blend those samples over time, smoothing out the reflections during camera movement.
The Shader Interaction
Remember that SSR relies on your material's Smoothness value. A rough surface (Smoothness = 0) will discard SSR data, while a mirror-like surface (Smoothness = 1) will use it fully. You can test your setup by creating a simple "Mirror" material:
// Conceptual logic within the Fragment Shader
float4 color = tex2D(_MainTex, i.uv);
float3 reflection = SampleScreenSpaceReflection(i.screenPos);
return lerp(color, reflection, _Smoothness);
By balancing the reflection intensity in your Volume settings against the Smoothness property of your materials, you can create surfaces that feel like they physically occupy the same space as your environment.
Key Takeaway: Screen Space Reflections bridge the gap between static lighting and dynamic reality by sampling the current camera view, allowing surfaces to react instantly to environment changes and camera movement.