I am trying to render out images of a quite complex archviz scene. It is a full interior (100m2 ish) and a small exterior environment with heavy foliage and nanite meshes.
I want to use the path tracer with the Movie Render Queue but it keeps crashing, even if I hide all foliage and most of the heavy nanite meshes. It crashes in 1080, 1440 and 2160p.
I love UE and all its amazing features, but I have to say that I have had a really bad experience with the MRQ so far. There is always some problem. Either crashes, fireflies, strange black artifacts, flashing lights, the list goes on. It takes so much energy and I often end up quite angry.
Just want to put this out here. Thanks for an amazing job with the rest of the engine.
Hey @Skybalotte
Im having the same issue on my 2080ti. MRQ will crash everytime I try to render anything through it, however the legacy renderer still works.
We tried MRQ on a beefier pc with a 3090 and it still wont run without crashes.
I’m convinced its problem with Unreal core as the error log shows that my VRAM is maxed out, even though GPU-Z reports that only 50% was actually in use.
Very strange issue that I’m hoping someone can shed light on as my time with MRQ feels like an abusive relationship.
This problem is present at least since 5.0 probably before that too. Increasing spatial samples will cause some excessive memory usage and that memory isn’t freed even after done rendering.
You can sort of workaround the issue by using a combination of low spatial samples and more temporal samples in AA settings of MRQ.
However if your scene has difficult lighting setup then you might be out of luck as using low amount of spatial samples might not provide enough exposure in some dark areas.
Legacy sequencer output does not have this issue and if your scene/ animation does not invalidate path tracer then you should be able to render out stills with high amount of samples. On top of that the output is also much sharper than the one from MRQ (mrq applies some weird image pixel filtering or something where you just won’t get sharp image from path tracing)
I honestly don’t understand how is it possible for such issue to persist through multiple stable releases of the engine. I guess not many people care about path tracing for epic to look into this…
Amazing, you just expressed my thoughts. It is ridiculous - I even make simple F9 screenshots from my 4k monitor instead using the MRQ. Because F9 is stable. If I use MRQ for PT stills - almost every time UE crush. If I use only temporal samples - exposure and colors in the final render became just disgusting. A temporary solution using 4848 spatialtemporal sampling but here we facing a denoiser problem. Denoiser activates every time when finishing one of 48 temporal samples.
Another issue MRQ is - inaccurate picture board - every time I get a black row (or column) 1-pixel width.
UE path tracing - is an awesome tool but still has a lot of issues.
So this is still the same issue. It is stuck in cut stage: Motion Blur (even though i deactivated motion blur)…and during this process the shared video memory is slowly filling up. Once this hits the limit it crashes. Note that this is not the vram filling up, its the shared video memory that is bound to RAM.
I come from classical rendering and I have no explanation for this. Should simply not happen. And I’m running a 4090 and it happens on an empty scene with a single light and no textures.
Also strange that I don’t find much about this issue. Maybe I’m missing sth obvious here. Dispatch size and flush have no influence btw as it doesn’t even get to this stage. Furthermore there is nothing about this even remotely related on the UE bugtracker.
I’m gonna make a more detailed post about this later today or when i find the time
My guess it’s a memory leak no one cares about as not enough people use PT and also if you stay within low values for spatial sampling and only increase temporal samples it’s ok.
However unlike deffered renderer you can’t just rely on temporal samples all the time…
Anyways I think we get sooner some faster rendering and denoising for PT rather than a fix for this.
yes its a memory leak, happens to me in both gpu(4090) and ram.
I was able to at least handle the ram memory leak by using a program called “lasso smarttrim
management”.
this clears periodically the memory Unreal is using for rendering, was able to
reduce crashes and get a few renders finally done! hope this is helping somebody.
