Warning Num Samples Per Thread Reduced To 32768 Rendering Might Be Slower |top| Jun 2026

If you manually set your render samples to an astronomical number (e.g., 40,000 or higher) without utilizing adaptive sampling, Blender is forced to split the workload inefficiently. Why Does It Make Rendering Slower?

In long, high-sample renders (e.g., 4096 samples per pixel), the overhead becomes a smaller fraction of total time, so the warning might be negligible. But for animations or interactive preview rendering, it can be frustrating.

Restart your computer. This allows rendering engines to raise their internal thread limits without triggering system instability. Conclusion

A: Absolutely not. num_samples_per_thread is about batching work, not the total samples per pixel. Noise remains unchanged. If you manually set your render samples to

[ Your 3D Scene Assets ] -> Exceeds Physical VRAM -> V-Ray Triggers Safety Mode -> Samples Throttled to 32,768

In short: The renderer wanted to assign a larger workload per thread (to reduce overhead), but it couldn’t. So it falls back to a smaller chunk size of 32768 samples per thread.

If you manually increase the setting in the renderer’s advanced options (e.g., in Blender’s Cycles > Performance > Threads), setting it above 32768 will trigger this warning because the engine cannot exceed its internal limit. Even if your hardware is powerful, the software itself may have a hard upper bound. But for animations or interactive preview rendering, it

: Close other VRAM-heavy applications (like web browsers or other 3D software) to free up memory for the renderer.

The warning message is a critical performance notification generated by the V-Ray GPU rendering engine . It alerts 3D artists that the graphics card has run out of dedicated Video RAM (VRAM) to execute the scene's path tracing at full speed. To prevent a hard crash or an "Out of Memory" error, V-Ray automatically shrinks the data workload handled by each GPU execution thread down to a baseline floor of 32,768 samples .

This is for production; it’s a debugging tool. Conclusion A: Absolutely not

To help diagnose the exact bottleneck in your project, let me know:

This is the #1 culprit. When rendering with GPU (CUDA/Optix), each thread needs a certain amount of VRAM to store sample data, ray states, and temporary buffers. If your scene is heavy—high-poly geometry, 4K/8K textures, complex shaders, volumetrics—the GPU might not have enough free memory to handle the desired samples per thread. The driver then forces a reduction.