topic Re: XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters in Maya Programming Forum

XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters

swflyKXVT3 — Fri, 05 Sep 2025 10:56:33 GMT

Hello,

We’re integrating XGen via XGenRenderAPI for our own renderer. Parsing works, but when artists edit XGen parameters and we re-parse in the same Maya session, XGen emits repeated errors:

“clumping guide ID larger than number in xuv file”
Deleting .xuv before parse avoids the error. In Arnold, when caches are stale, we see:
[xgen] Batch mode tests failed! proceeding with Xgeneration... using live scene data
— which appears to force a “live scene data” path and avoids stale clump caches.

What we’re doing:

auto* patch = XGenRenderAPI::PatchRenderer::init(&cb, cmd.c_str());
auto* par = XGenRenderAPI::ParallelRenderer::init(patch);

cb implements ProceduralCallbacks (flush/log/get* etc.). Even with an empty flush(), the stale .xuv issue persists unless we delete them first.

The question is:

How to trigger “live scene data” reliably from a third-party renderer? Is there a documented cmd string or flag for PatchRenderer::init(...) to bypass batch caches and use live scene data (like MtoA’s fallback), or is the intended approach to fail batch validation and let XGen switch internally?
Best-practice cache handling: What is Autodesk’s recommended approach to avoid clump ID desync without deleting user .xuv maps? For example, does XGen provide a supported API call to regenerate clumping maps programmatically or to redirect the clump “Points Dir” per-parse to an isolated location?

Thank you very much.

Re: XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters

957714080 — Tue, 09 Sep 2025 04:01:22 GMT

I also encountered the same problem

Re: XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters

cheng_xi_li — Tue, 09 Sep 2025 06:51:14 GMT

Hi,

In XGenRenderAPI::ProceduralCallbacks, there is a callback

bool Procedural::get(EBoolAttribute in_attr) const

You can try to return true when the in_attr is ClearDescriptionCache. It will cause XGen render reloading the description.

You can use mtoa's handling policy. When it isn't exporting a file or a batch session, it will always try to clean the cache first.

Hope it helps.

Yours,

Re: XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters

957714080 — Tue, 09 Sep 2025 06:50:05 GMT

Thank you, it can be resolved. That's great

Re: XGenRenderAPI::PatchRenderer causes clumping guide ID error after editing xgen parameters

swflyKXVT3 — Tue, 09 Sep 2025 08:04:11 GMT

Thanks this totally solves the problem.