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

The warning typically occurs in V-Ray or similar GPU-accelerated renderers when your scene is reaching the memory (VRAM) ceiling of your graphics card . Why This Happens

If you have an 8GB GPU and a 4GB GPU, the renderer must fit batches on the smallest card. It will lower num_samples_per_thread to the 4GB card’s limit, even though the 8GB card could handle larger batches. The warning will appear, and the faster card will be underutilized. The warning typically occurs in V-Ray or similar

At first glance, it sounds intimidating. Is your hardware failing? Did you misconfigure a setting? The good news is that this is usually a protective measure, not a critical error. However, ignoring it could leave performance on the table. The warning will appear, and the faster card

Are you a graphic designer, animator, or video editor who's encountered the warning message "Num samples per thread reduced to 32768 - rendering might be slower"? If so, you're not alone. This warning can be frustrating, especially when you're in the middle of a critical project with a tight deadline. In this article, we'll explore what this warning means, why it happens, and most importantly, how to address it to ensure optimal rendering performance. Did you misconfigure a setting

If you’re using GPU+CPU hybrid, switch to GPU-only. Or switch from CUDA to OptiX (for RTX cards). You might find one combination avoids the warning entirely.

4K or higher textures can quickly fill VRAM.