2.66, Cycles is Stuck Synchronizing Objects

So i’ve been trying to render a few scenes that I’ve been workin on. They work fine in the viewport render, but as soon as i press f12, cycles starts to synchronize the objects and does this for hours…sometimes it just crashes before it’s done and i dont even get to see my render :frowning: anyone having these problems or know how to fix this?

I am having this problem too! I need help! (don’t kill me for bumping it up, it better then a posting a new thread)

Sounds like you are running out of RAM.

It eventually renders, it just takes a really long time. like 30 minutes

How much memory do you have and how complicated are the scenes?

Not having enough RAM will do that. At the top of the render screen, it will show peak memory usage. Compare that number, with teh RAM in your machine and you will know.

Viewport render uses the geometry already in memory. When you render with f12 this geometry data is copied again to an external buffer for Cycles to use. This means you are using twice as much memory to f12 render. On top of this, it sounds like you have some serious overuse of the subsurf/multires modifiers somewhere if you’re seeing 30 minutes to sync.

I’ve also found out that the synchronization stage can take up to 20-30 times longer if you have objects not only making heavy use of modifiers, but also using tangent-space normal maps (perhaps because the UV’s are also subdivided and it has to calculate the coordinates for each one).

Luckily, the current builds have an awesome new input for the bump node that creates normal-map like quality from a simple bumpmap, so I would just use that instead until Brecht finds a way to optimize the synchronization stage.

Thank you everyone for responding. I am using subsurf at level 6 with lots of normal maps and displacements. so I know the problem now.

Thanks everyone!

But there’s a bigger issue I think. Why is it necessary to synchronize before every single frame? Clearly, in the viewport, Blender can accomplish the render without having to resync. Can’t someone reprogram F12 to work more like the viewport? Can anyone think of a workaround where you can render an animation through the viewport instead of using F12?