Screen Space vs Raytraced Reflections in Blender

In Blender, reflections are essential for creating realistic materials and lighting, and they are primarily calculated using either screen-space reflections (SSR) or raytraced reflections. While SSR calculates reflections based only on what is currently visible within the camera view, raytraced reflections simulate actual light paths interacting with the entire 3D scene. Understanding the fundamental differences in how these two techniques operate, their performance impact, and their visual fidelity will help you choose the right method for your rendering pipeline.

What Are Screen-Space Reflections (SSR)?

Screen-Space Reflections are a real-time approximation technique commonly used in Blender's EEVEE render engine. SSR works entirely in post-processing by analyzing the pixels currently visible on the screen (the "screen buffer"). When a reflective material is rendered, the engine samples existing pixel data within the camera frame to generate the reflection.

• Speed: Extremely fast and efficient, making it ideal for real-time viewport feedback, motion graphics, and video game asset previews.
• Limitations: SSR cannot reflect anything that is off-screen or occluded by other objects. If an object moves outside the camera frame, its reflection will instantly vanish. It also suffers from noticeable edge fading and distortion artifacts near the borders of the render.

What Are Raytraced Reflections?

Raytraced reflections, primarily utilized in Blender's Cycles engine (and increasingly integrated into modern real-time workflows), physically trace simulated rays of light from the camera into the 3D scene. When a ray hits a reflective surface, it bounces based on the material's roughness and surface normal, detecting any geometry it strikes regardless of its position relative to the camera.

• Accuracy: Captures accurate global reflections, true multi-bounce reflections, complex refractions, and surfaces hidden from the camera's direct line of sight.
• Limitations: Highly demanding on system resources. Raytracing requires significantly more compute power and longer render times, often necessitating hardware acceleration (such as NVIDIA OptiX or AMD HIP) to render efficiently.

Key Differences at a Glance

• Scene Awareness: SSR is limited to 2D screen information; raytracing calculates the entire 3D scene geometry.
• Off-Screen Objects: SSR cannot reflect off-screen objects; raytracing reflects all active scene objects, even those behind the camera.
• Occlusion: SSR fails when a foreground object blocks a background object from the camera view; raytracing naturally handles foreground and background occlusion.
• Performance Impact: SSR offers near-instantaneous viewport rendering with minimal hardware load; raytracing produces higher render times and requires denoising to eliminate grain.

When to Use Each

Use Screen-Space Reflections when working with tight deadlines, real-time animation previews, stylized projects, or when rendering on lower-end hardware where maximum render speed is preferred over absolute physical accuracy.

Use Raytraced Reflections when producing final production frames, photorealistic architectural visualizations, scenes with flat mirrors, or environments with complex interior lighting where missing reflections would break immersion.