Blackmagic Forum

Hello,
new to DR, editing my first project and cache behavior bothers me much. Went through different settings and different tutorials but couldn't make it work to my (at least partial) satisfaction.
The thing is, rendered cache is extremely volatile. Whatever I do, cache immediately breaks down and DR renders it all over again.
Instances:
1 - I have a timeline with rendered cache. I make a (safety) copy of this timeline and carry on with the copied timeline. Cache is gone, unnecessary render starts.
2 - I change something at the very end of my timeline and the ENTIRE timeline cache breaks down, new render commences. I do not get it... why on earth it drops totally perfect render when nothing changed on that particular section?, better said, 99 percent of my timeline hasn't changed at all.
3 - I accidentally touch a clip, cache breaks (that's fine) but after undo (Ctrl+Z) the cache won't come back and renders again...

there are many similar situations when rendered cache breaks down immediately and I am constantly delayed by a new render.

Am I missing something crucial in the software philosophy? Or am I getting the settings wrong? I am totally confused and missing the point this behavior.
I edit in Media Composer and here I can RENDER the timeline, meaning the renders are rock solid and stick to the timeline until I change something. After such change, only the necessary part of the render breaks down (and not a single frame more!!!). I seek for some similar setting. In DR, I am afraid even to breathe or blink my eye as it precipitates new cache render immediately.

Is there a reasonable way to edit in DR? I mean something once rendered stays renderd if not touched?

Thanks in advance for enlightening me

None of those are normal. Are you using 17.2?

Sorry for my late reply. Email notification ended up in my spambox...

Yes, I am running 17.2 on Win10 build 1909.
C SSD drive is Sysyem/Win10
D SSD drive is media
E SSD drive is for renders

Same thing here, since the 16.x versions. I always had the impression that the rendering cache is more related to time than pixel changes. I'm not sure, but I believe it is based on the track and not the clip.

One thing I do here is never use Smart cache render. I always leave it to User. I was surprised by the amount of things that I can playback in real time without needing the cache, even if in Smart mode, DR constantly asks to do the cache. Which, in some situations, greatly reduces the number of areas that really needs to be render.


i7 3.5
GTX 1050 Ti 4Gb
16gb RAM
WIN 10
DR 17.2

Cache is tied to the timeline's timecode rather than specific clips. Any changes to that frame in the timeline will generate new Cache for that segment.

That said, when I copy a timeline with Cache, that Cache is also copied.

If I change the last clip in a Cached timeline, only that last clip is re-Cached. (You don't have anything like Adjustment Clips over the entire timeline, do you?)

If I undo a change, the Cache does come back.

Yes, I thought so. Although I think it has its advantages, it would be great a option that would allow us to choose between track based and clip based, similar to flame. In some situations it is more advantageous to have a longer rendering time, but persistent, than a faster and more volatile rendering.

Well, there’s Render in Place in 17.

Testing anew in 17.2, I may have the wrong understanding of Cache here.

Once the Cache was rendered for a clip, it did in deed follow that clip around. This was true for both Fusion and Color Cache.