V-Ray Tip: Optimizing V-Ray GPU Out-of-Core Textures

Out-of-core textures let V-Ray GPU render scenes that exceed your GPU’s VRAM by paging textures from system RAM. Used wisely, it prevents memory errors with minimal impact on quality.

• When to use: massive UDIMs, 8K–16K assets, large environment sets, heavy lookdev with multiple high-res variations.
• When to skip: small scenes that fit comfortably in VRAM—out-of-core paging adds overhead and can slow IPR.

How to enable (host-agnostic):

• Switch the renderer to V-Ray GPU (CUDA/RTX).
• Open V-Ray GPU settings and enable the out-of-core option for textures.
• Enable on-demand mip-mapping to stream only the necessary texture resolution per pixel.
• Set the GPU texture cache size to leave headroom for geometry, denoisers, and frame buffers (a practical starting point is ~50–70% of available VRAM).
• Restart IPR/production render after changing memory settings.

Key best practices:

• Prioritize mip-mapped inputs: Use VRayBitmap/VRayHDRI (or their host equivalents) so V-Ray can efficiently generate and use mip levels.
• Choose efficient file formats: Albedo/roughness/metalness: 8-bit sRGB (PNG/JPG) is usually enough. HDRs, normal maps, displacement: 16-bit Half EXR is a good balance of precision and size.
• Right-size textures: If a hero object needs 8K, background variants likely do not. Downscale non-hero maps for drafts and keep a high-res version only where it impacts the frame.
• Curate UDIMs: Remove or disable tiles outside camera coverage; keep only tiles contributing to the shot.
• Avoid redundant variants: Use procedural masks, Triplanar, and tiling with randomization instead of loading many similar high-res bitmaps.
• Reserve VRAM for the critical path: Keep glass/skin/specular response textures in-core if possible; let less-visible textures spill out-of-core.

Performance and stability tips:

• Monitor memory: Watch the V-Ray log/VFB stats for VRAM and out-of-core usage. If paging spikes, reduce texture sizes or cache size.
• Balance multi-GPU: Each GPU manages its memory independently; ensure your system RAM is sufficient for the number of GPUs when out-of-core is active.
• Avoid fragmentation: Very large uncompressed TIFFs can bloat memory; prefer EXR or compact 8-bit where quality allows.
• Test at final res early: A quick region render at target resolution reveals whether mip levels and cache sizing are effective before full frames.

Troubleshooting:

• IPR feels sluggish: Lower texture cache usage or temporarily disable out-of-core during lookdev; re-enable for final frames.
• Paging thrash: Downscale the few largest textures, prune UDIM tiles, or increase system RAM to give the out-of-core pool breathing room.
• Unexpected noise: High paging can increase variance; tighten the Noise Limit slightly or enable a fast denoiser for previews.

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