Slow-rendering thumbnails can be queued up for real-time updates

A licensee is seeing performance drops while using the editor due to a custom thumbnail renderer taking a while to generate thumbnails while Real-Time Thumbnail rendering is enabled, and has requested that UThumbnailRenderer have some additional logic to gate potentially expensive thumbnail rendering operations from being performed in real-time, even with real-time thumbnails enabled.

The following options were suggested:

In UThumbnailRenderer, add an IsSlowToGenerate() method:

virtual bool IsSlowToGenerate const { return false; }

And use it within FAssetThumbnailPool::Tick() to gate any expensive thumbnails from being added to the RealTimeThumbnails list:

if (!RenderInfo->Renderer->IsSlowToGenerate())
{
RealTimeThumbnails.AddUnique(InfoRef);
}

Alternatively, in UThumbnailRenderer, add a GenerateForContentBrowser() method:

virtual bool GenerateForContentBrowser() const { return true; }

And check if a thumbnail should be generated when checking if the renderer is valid for an asset within AssetThumbnail.cpp:

if (RenderInfo != NULL && RenderInfo->Renderer != NULL && RenderInfo->Renderer->GenerateThumbnailForContentBrowser)) { /*...*/ }

See UDN link. Issue has the possibility to affect custom thumbnail renderers