Setting an external GI cache

To render using a previously computed GI cache:

// "win" is a pointer to a RED window.
// "viewpoint" is a pointer to a scene viewpoint.
// "gi_cache" is a pointer to a previously computed GI cache.
RED::IWindow* iwin = win->As< RED::IWindow >();

RED::Object* vrl;
RC_TEST( iwin->GetDefaultVRL( vrl ) );

RED::IViewpointRenderList* ivrl = vrl->As< RED::IViewpointRenderList >();

RC_TEST( ivrl->SetViewpointGICache( gi_cache, viewpoint, iresmgr->GetState() ) );