Ground lines with Ds 4.10

Navi

Hello,

There are some lines on the ground in all renders I make when a paper backdrop is used, after upgrading to 4.10 a couple months ago (it never happened with the previous version I had, 4.8). I didn't notice it before because it doesn't seem to happen on prop backgrounds; only on backdrop types of background for some reasons (light is an hdri, just in case). Does anyone have an idea on what might be causing this ?

Thanks :)

Navi

ps : A detail I forgot, in 4.8 and previous versions, this backdrop did produce a smooth and blurred shadow, in place of the harsh lines we see here on the ground.

JonnyRay

How is the backdrop constructed? Is it two planes meeting at an angle (like a wall and floor) or does it curve where it transitions from horizontal to vertical?

TBH, this looks a little like issues we used to have in 3Delight where shadow biasing would create banding instead of smooth transitions. But I assume this is an Iray render?

Navi

Yes this is an Iray render, and I don't know how was made that backdrop exactly, it seems to be properly curved, and not made of 2 planes intersecting, but I have no clue if there is something about it that Iray [starting with versions later than 4.8] don't like. All I know is that it used to work fine with versions up to 4.8. That scene itself is the same old scene that was often used in 4.8, that was re-opened in 4.10 today.

In any case, your comment makes me think I should try to render the scene with another backdrop perhaps :) , thanks !