[top] | Warning Num Samples Per Thread Reduced To 32768 Rendering Might Be Slower

In Blender Cycles, large tile sizes (e.g., 512×512) tend to increase per‑thread sample counts. Smaller tiles (e.g., 256×256) may stay under the limit. Experiment:

If you encounter this message frequently, you can optimize your scene using these methods recommended by Chaos Support Switch to Progressive Sampler Progressive Image Sampler

Understanding the "Warning: num samples per thread reduced to 32768" Error

In this post, we’ll break down exactly what this warning means, why it happens, and—most importantly—how to fix it. In Blender Cycles, large tile sizes (e

If you have access to the rendering settings (e.g., in a custom script or application), reduce the requested samples per thread to . Ironically, matching the cap avoids the warning and the overhead of automatic reduction.

“How much slower?”

A: It’s purely informational. Unless you are actively performance tuning, you can ignore console output. If you have access to the rendering settings (e

When a renderer tries to process a scene, it attempts to load all necessary data—geometry, textures, and displacement maps—into the GPU's video memory. If the scene is too complex for the available VRAM:

This warning is essentially a symptom of . If you see this, your GPU has likely run out of space to hold all the data necessary for the current render frame. Extremely High-Resolution Rendering: Rendering at , or higher requires massive VRAM for the frame buffer. Too Many High-Res Textures:

When that limit drops to 32,768, two things happen at once: Unless you are actively performance tuning, you can

This warning, most commonly seen in and occasionally other GPU-based renderers like

Some renderers allow you to set the per-thread sample limit directly. For example:

He heard Mira type. Then a new warning flashed: