NVIDIA-Omniverse FSD Configurator
The Fabric Scene Delegate (FSD) is the modern rendering pipeline. Most performance questions touch FSD configuration in some way.
The default-first principle
Recommend that users keep defaults unless they have a specific reason to change them. When a setting must be changed, recommend leaving a comment in the .kit file explaining why — feature, bug being worked around, or expected future fix. That comment is what lets the flag be removed later when the underlying issue is resolved.
The settings table below is intentionally narrow — it surfaces only the flags partners actually need to consider. Most other FSD-population flags should stay at their defaults.
Configuration reference
| Setting | Path | Default (Kit 109+) | Recommendation | Status |
|---|---|---|---|---|
| Enable FSD | /app/useFabricSceneDelegate |
true (Kit 109+), false earlier |
Always on | — |
| Merge materials | /app/usdrt/population/utils/mergeMaterials |
false (Kit 108+), true earlier |
Opt-in optimization — enable for static stages with many duplicate materials, not using NeurayLib materials | Off by default since Kit 108 |
| Renderer-side instancing | /app/usdrt/population/utils/enableRendererInstancing |
false |
Test on heavily-instanced scenes | ⚠️ Experimental, RTX renderer only |
| Populate all authored attributes | /app/usdrt/population/utils/populateAllAuthoredAttributes |
false |
Off for rendering. Enable only when you specifically need custom attrs in Fabric — costs memory | — |
| Instance compact transforms | /app/usdrt/population/utils/instanceCompactTransforms |
n/a | Do not use | 🗑️ Deprecated since Kit 108.0 |
The mergeMaterials default (most common partner question)
mergeMaterials has been off by default since Kit 108 (it was true in earlier versions) — that's the stable default, not a temporary flip. It deduplicates identical materials to save memory, but it is incompatible with NeurayLib materials and affected variant/material-swapping content (notably automotive configurators), which is why it ships off. Treat it as an opt-in optimization.
- Static stages with many duplicate materials and no NeurayLib materials should turn
mergeMaterialson — such stages can load noticeably faster with it enabled. - Content using NeurayLib materials or variant/material swapping should leave it off.
The instanceCompactTransforms story (frequently misunderstood)
This setting is deprecated since Kit 108.0. Older guides and templates that recommended setting instanceCompactTransforms=1 are stale. Strip it from .kit files when you find it. It is mutually exclusive with useMatrixForInstanceProxyTransforms, which is the recommended path now.
Do not list it as a recommended memory-optimization flag.
Launch-flag block (when needed)
# FSD master switch
--/app/useFabricSceneDelegate=1
# Opt-in optimization: mergeMaterials is off by default (Kit 108+).
# Reason: static stage with many duplicate materials, no NeurayLib materials.
--/app/usdrt/population/utils/mergeMaterials=1
# EXPERIMENTAL: validate before shipping. RTX renderer only.
--/app/usdrt/population/utils/enableRendererInstancing=1
Always include the # Reason: comment when generating launch-flag blocks for users — that's the convention for this guide.
Do / Don't
- ✅ DO verify FSD is enabled on existing apps. Older Kit App Template branches may have it explicitly disabled by workarounds.
- ✅ DO quote full setting paths verbatim (
/app/usdrt/population/utils/mergeMaterials, never justmergeMaterials). - ✅ DO leave a comment in the
.kitfile when changing any FSD setting. - ❌ DON'T disable FSD unless there's a specific, documented reason. The OmniHydra fallback path is legacy.
- 🗑️ DON'T recommend
instanceCompactTransforms=1. Deprecated since Kit 108.0. - ⚠️ CAUTION when recommending
enableRendererInstancing— experimental and RTX renderer only.
Source guide section
docs/reference/platform-systems.md.
External reference: FSD Configuration & Settings.