Rendering issue with 5.6 - Path Tracer , RT Shadows

Hi, I’ve been starting a car render project on 5.6 but one of my mesh doesnt react properly with ray traced shadows and path tracer (invisible in path tracer, invisible in lumen overview, and as such no cast shadows with RT shadows activated)

I tried to import the same mesh on 5.5.4 and everything seems working fine. (I tried megalight on both, doesn’t seems to change anything)

What’s even stranger is that it only happens on a single mesh, other models seems fine. I tought it may be because of polycount on this specific car but looking at the wireframe they all seems pretty high poly.

Maybe it’s just a bug or is it something i don’t do correctly/don’t understand ?

Some screens from 5.6:



And in 5.5 working fine (RT SHADOWS ENABLED) :


thanks in advance for any help

Is that one mesh Nanite enabled? If so, try setting r.raytracing.nanite.mode 1 CVAR.

It is Nanite, i tried r.raytracing.nanite.mode 1 but doesnt seems to change anything

btw nanite seems to be at fault also on this mesh, bc it works well with RT shadows and Lumen when disabling it