Objects Flickering Behind Glass

[Mike Truly]

Vray 2.4

I have a simple animation of a vray physical camera which moves from pointA to pointB while it looks at a building. As the animation proceeds, you can see through a glass door a workbench which is in the garage.

I can see a lot of difference in the shading of the workbench between frames. This shows as a kind of flickering as you see the differences between frames. Here are 3 frames... f135, f136, f137.

It's a bit hard to tell, but the workbench behind the glass door is different in each frame... which results in the flickering.

Is there a particular render setting that would make the rendering of the inside of the garage more consistent?

Thanks for any ideas!

[notamondayfan]

Can you post your render settings, GI settings, etc

[Mike Truly]

Sorry, attached is a screengrab of the settings. This is a simple setup of a vraysun and vraysky with GI on.

As the camera moves past the building, the large windows show the interior of the building with light and shadows inside and this area is not flickering. But as the camera moves past the garage, the interior of the garage is darker with less direct light inside and the rendering differences per frame result in flickering of the workbenches, floor, etc. The large car garage door is open on the opposite side of the garage and some GI light is going inside... but overall, it's darker in the garage than the house.

Thanks!

[Mike Truly]

I tried doubling the vraysun shadow subdivisions to 32... no change.

I re-rendered the animation without the glass visible (it has nothing to do with the glass obviously). Here you can see frames f140, f141, f142. Notice the differences of the workbench area between frames. Notice the light changes on the wall above the workbench viewed through the window. Notice the small burp of light appearing on the wall above the workbench viewed through the door on f142.

The net effect of these differences between frames is a spastic flickering inside the garage (particularly in the workbench area).

Nothing moves or changes in the animation except the camera.

Thanks!

[joconnell]

I'd bake your gi and light cache then, if you still get errors in the render its likely bad geo causing raytracing problems.

[Mike Truly]

Thanks for the ideas! I will consider this. But at this point, I want to find the settings to resolve this without baking.

I turned OFF the vraysun and left only the GI ON. I get this splotchyness in the garage floor. The garage floor is a plain gray vraymtl with no mapping at all at this point. What causes the splotchyness?

Thanks!

[M.Max]

Irradiance map by it's nature is super fast, But not accurate and would change from one frame to another randomly.
To avoid flickering you will need to "Cache" the GI calculations into one file and load that for the entire animation so it is static.
If you are not familiar with caching process take a look at the official documentation tutorials section. It might look long process, but once you get it you will find it so easy to do.

As for the floor issue, are you sure there is no overlapping faces there (vray plane at the same level)

[joconnell]

Yep - as max said above, irmap is inherently slightly different at each frame so the flicker is built into it - there's a few situations where you might get away with this (animated character moving around outside for example) but for a static scene with a moving camera, having the solution change every single frame will kill you. To stop flicker, you calculate enough frames so that the camera has seen every possible visible part of your shot and then you lock / cache this solution. It gets you a beautiful combination of quality and speed that aren't possible any other way and the irmap is designed to fulfill exactly this task. I don't think you'll ever find a combination of settings that'll give you flicker free results that aren't so extremely high that you wouldn't have done better with brute force as your primary GI.

I'm using baked / cache irmap and light cache on a huge vfx film right now and have done on many other huge vfx films and it's not because I can't find the settings to make it not flicker, it's just that it wasn't designed to work per frame on architectural jobs anyway.

Don't bang your head off the wall for zero benefit, give this section of the docs a quick read and you'll laugh at how much easier your life will become! https://docs.chaosgroup.com/display/...pandLightCache

(doesn't matter that it's vray 3, it hasn't changed since 2)

[Mike Truly]

Thank you very much for these ideas and explanations! I will dig into this info further. I will check the geometry again but I'm pretty sure my models are clean.

Thanks again.