Slow rendering of high resolution images

[anton taf]

I'm having a lot of difficulties with high resolutions. Is this normal for now? I'm rendering in 3500x2300 and it's very slow. It took me almost 2 days for one render to reach 6% noise. I have a lot of plantation and it's a big scene, but it seams not normal. In resolution 2880x it renders fine...
c4d r17.055, corona DailyBuild 2017-05-17, dual xeon pc, 32gb ram.

How can I check which objects or areas slows down the scene so I can optimize it? Is there a Multipass channel for this?
Also for exterior shots with plantation I'm using Path Tracing solver. I think this is better right? Thanks

[fabio81]

Yes, with high resolution is very very slow .. hopefully in the future it will solve ..

[houska]

I'm having a lot of difficulties with high resolutions. Is this normal for now? I'm rendering in 3500x2300 and it's very slow. It took me almost 2 days for one render to reach 6% noise. I have a lot of plantation and it's a big scene, but it seams not normal. In resolution 2880x it renders fine...
c4d r17.055, corona DailyBuild 2017-05-17, dual xeon pc, 32gb ram.

How can I check which objects or areas slows down the scene so I can optimize it? Is there a Multipass channel for this?
Also for exterior shots with plantation I'm using Path Tracing solver. I think this is better right? Thanks

It shouldn't be a problem. 2 days is really weird... What are your render times up until 6% noise with the 2880x... resolution? And yes, for exteriors, UHD cache should not give any significant benefit.

[anton taf]

I'm attaching a screenshot of my scene (in ID channel) to have an idea of my scene size.
You can see the rendering time at the moment is 1:26, 13 Passes rendered, 11,89% noise level.
I think this is kind of normal. The problem is when I want higher resolution...

[Ondra]

rays/s is way too slow, what is your RAM and CPU usage?

[anton taf]

rays/s is way too slow, what is your RAM and CPU usage?

I'm attaching two more screenshots with cpu and memory usage.

[Shawn Astrom]

I'm having a lot of difficulties with high resolutions. Is this normal for now? I'm rendering in 3500x2300 and it's very slow. It took me almost 2 days for one render to reach 6% noise. I have a lot of plantation and it's a big scene, but it seams not normal. In resolution 2880x it renders fine...
c4d r17.055, corona DailyBuild 2017-05-17, dual xeon pc, 32gb ram.

How can I check which objects or areas slows down the scene so I can optimize it? Is there a Multipass channel for this?
Also for exterior shots with plantation I'm using Path Tracing solver. I think this is better right? Thanks

I can also confirm that once you need to render above a certain resolution like 4096 for example Corona brings my 40-core machine to a stand still... Whole computer becomes very unresponsive... I tried limiting the amount of cores and Corona still get weird and slow at higher resolution renders...

- Shawn

[4b4]

I'm on a i7-4930 but get a similar problem however I've found culling down the number of lights really helps on some scenes. Appreciate this isn't always possible but I noticed a very high light count in the screen grabs, can you reduce this down (even temporarily) to see if that speeds things up?

[anton taf]

What I do to optimize my scene are the following:
1. I use render instances for all plants and trees, or forester plants.
2. I use for grass, 3 different resolutions of the grass based on the distance from camera (LOD).
3. I create instances (not render instances) for each corona light that is repeating. (and I add the source light + the instances in the LightSelect...)
4. I merge as many as possible objects in one.

On the other hand, I have many Light Selects in Corona Multi-pass and I have many objects in the scene, that I turn off depending on the camera I use each time. (Here I try to use the Take system, but as I said in a previous post I have some issues with this. Or I'm not sure if it's this, but I think it slows down even more the rendering)
Also I'm using Vertex Maps for the scattering (I don't know if this has to do with the speed...)

[anton taf]

I'm on a i7-4930 but get a similar problem however I've found culling down the number of lights really helps on some scenes. Appreciate this isn't always possible but I noticed a very high light count in the screen grabs, can you reduce this down (even temporarily) to see if that speeds things up?

What I didn't do is to Uncheck all LightSelects (from Multi-pass) that I have off for the current camera. I will try this and see how it goes, thanks

[TomG]

Tried a simple scene (HDRI + Corona Sun, interior) at 16,000 x 9,600 resolution. One thing I note is that your CPU is only showing 50% utilization.

Will see if I can test with render elements and / or more lights. BTW what render elements do you have set up in the Corona Multipass?

[anton taf]

Ok now it looks much better.
I unchecked all unused LightSelects and deleted all Takes. I'm not sure if the Takes have to do with it. But the lightselects for sure.
I don't know about the Utilization of my CPU. Now it is 100%. I didn't change anything for this. (The Virtualization setting has any affect in the rendering?)

Just to note here that I had more than one Suns, Skies and HDRi in the same LightSelect (see image below - With one of them On at a time). Also in the render that took me almost 2 days I had DOF on, with more lights in the interior (also exterior shot). In this one I have DOF off with just two lights + hdri.
I use very basic passes as you can see. ID, Reflect, ZDepth and lightmix.

I will retry again the other camera and check if the number of lights causes a lot delay. Thanks

[Nejc Kilar]

@anton taf If I may have a crack at your problem as well... Your disk usage is off the charts in each of your screenshots. That usually happens when you run out of RAM - probably due to the exterior scene and a lot of lights active in lightmix. I do see your RAM is below 90% for the most part but it might have already offloaded most of the content back onto the HDD / SDD drive.

As for problems with Corona being slower when rendering big... I posted a similar topic under General as I have literal VFB / UI slowdowns when I render complex scenes. Funny stuff :)

[Rhodesy]

Yes I get those slow downs too. I appreciate there are a lot of calcs going on and more pixels to shift but it would be interesting to see if its the same on MAX. I would have thought the 2 corona VFBs would be identical as its all corona? Maybe its something to do with having to sync with the PV? Getting some better save options in the Vfb would mean we could ditch the PV and hopefully improve performance. But im only guessing at that.

[Nejc Kilar]

Thats the funny thing. 3ds Max works fine for me :) Smooth even with the IPR. In C4D however, if I render a 3k preview I sometimes (and it seems a bit random) can barely move the render region around.