I am rendering an animation and i have a problem or I don.t know if is a problem. Up there at the memory for this frame it says 5kM, the thing is that I also had the same memory usage for frame 1 that basically shows the whole scene with more objects, textures, shadows etc. Shouldn't the memory usage go down as you have fewer objects in your frame?
HI Gabriel,
I do not know what is measured there exactly...in the bottom right of your UI, there are RAM and VRAM shown during Renders and they tend to fluctuate more and get a lot higher...I simply ignore those on the top left...
I am sure someone here in this Community knows, what those values actually mean.
I think they should go down, but I think that Blender loads up the entire scene at the beginning and then starts rendering. So even though there comes a frame with less stuff in it, still Blender loaded the whole scene and that's where the memory usage came from. But I'm no tech guy, I barely know stuff like this, it's just that I remember the whole thing being discussed like that before.
I am writing this more to find if there are some way to change this (rendering the whole scene when you are focusing on fewer objects etc.) because I have problem with keeping my GPU memory constant. That is pretty much my limit. Rendering 160 frames all of them constant in memory (+/-400) I had times where I got GPU out of memory.
I found a quote from Stefan Werner:
"The window during rendering only shows the memory that the Cycles kernel itself allocated for rendering data. Depending on the settings, this may be system memory or VRAM.
This is by far not all the memory that Blender uses. Blender is further allocating memory for its data structures, for UI graphics, for geometry, etc. That is being tracked in the main Blender window."
So, (if I understand it correctly) those numbers have little to do, with you running out of VRAM.
...but now you're asking a completely different question: "How can I avoid running out of GPU Memory?"
First things that come to my mind are:
- Close every other application
- Do a UI-less (background) Render
- Try to reduce your amount of Polygons (Triangles actually)
- Simplify Shaders
- Render on CPU
- Use a Renderfarm
- Upgrade your computer
...and I am sure there are a lot more things you can do, the question is, how much do they affect VRAM usage...
No, it doesn't go down with cycles. Objects that are set to visible for render are still used to calculate indirect light and reflections even if they're not in the camera's view. There are probably other things that they are used for, but that's the 2 I know for a fact. As for running out of memory, 
spikeyxxx covers most of them, but I'd like to add one:Go to render tab on the performance panel's heading click the icon to the right of where it says performance and click the lower memory preset. This will increase render times. How much will depend on your GPU. Incase you want to know what this is doing it changes the tile size from 2048 to 512, and check use compact BVH.
One more: Under Output properties check "Render Region". It limits what's calculated outside the camera view. Helped me on my old clunker.