After never having an RTX card in my freelancing computer due to the chip shortage and scalping - I started a new job and finally got my hands on a machine with an RTX A6000 at the office.
On my latest project I thought I could take advantage of gpu mode for the setup and then switch to cpu rendering for the final image - not a unique workflow from what I'm hearing. But then I found my final images don't look anything like what I expected.
Upon further investigation I'm finding very inconsistent results between cpu and gpu rendering.
on some scenes you'd have to pixel-peep and split hairs to spot any difference, but on other scenes it's night and day.
Keyshot advertises "one-click" to switch back and forth between cpu and gpu, and while that's technically true, it's totally useless in my experience.
Switching between the cpu and gpu rendering engines may only take a single click, but then you have to readjust all the materials, environments and lighting and get the look and feel you're happy with, and more often than not you just can't get gpu and cpu to look similar no matter what you do (read ahead).
After seeing these differences I concluded I basically need to pick a rendering engine and stick with it from start to finish if I have any hope or expectation to the get a final image that resembles what I was seeing in my live-view.
I've heard and read that some variation between gpu and cpu modes was to be expected because of the way the different algorithms interpret the scene (or some sophisticated sounding reasoning along these lines), and that Keyshot makes an effort to make the two modes look as similar as possible. Well, in some cases it's not a matter of being as "similar as possible", it's a matter of being similar at all. And it's not just a question of brightness or contrast difference, it's all over the place.
For demonstration I built a test file and ran an experiment. Feel free to download the attached images and compare back and forth between them.
First observation is that cpu and gpu samples are not the same. It takes a lot more samples to get a smooth image on gpu rendering, and even at 4096 samples I still can't get a smooth edge on some materials (look at the pixelation / furriness of the edge of the glass and around the buttons on the top face of the cube).
Having said that, gpu samples on my machine are extremely fast (again no surprise here). I rendered 4096 samples on gpu much faster than 128 samples on cpu.
Lastly, it's not just a matter of scene brightness or contrast. the speculars and textures are just totally different in their own kind of way.. Even after trying to adjust the HDRI (brightness, contrast, and individual pins) I just couldn't get it to match. It's really a different animal.
Is anyone here having any luck utilizing both gpu and cpu modes in a single workflow? Are you getting any value from switching back and forth between them?
Same issue here, not sure why. I tend to start my projects with GPU only now so I don't have this issue anymore
I'm not here to defend the discrepancies between these two modes of rendering. However, I've also don't know anyone who switches between CPU and GPU mode on a single project due to the fact that they are not going to match. Basically, your computer is going to be faster in GPU mode or CPU mode from one scene to the next. Best practices would be to identify which one is better for your machine and just stick with it.
I know that's not ideal. I personally would love for the two to create identical outputs, but I'm not sure if that'll happen. I also don't know if other render engines that can run on CPU and GPU are producing identical results. Would be interested to know if that's the case.
I suppose where you can get into trouble is if you have a library of materials you use across multiple projects. Using those materials in scenes rendered on the CPU then later on the GPU will probably produce different results unfortunately.
To answer your question, no. I don't try using CPU and GPU rendering in the same workflow/project.
Unfortunately we have thousands of legacy images rendered in the before time so we must stick with CPU rendering because of the visual differences...
Perry
Quote from: BoazD on April 26, 2022, 09:40:16 AM
After seeing these differences I concluded I basically need to pick a rendering engine and stick with it from start to finish
Do that, and you'll be fine.
Quote from: Furniture_Guy on April 26, 2022, 12:42:16 PM
Unfortunately we have thousands of legacy images rendered in the before time so we must stick with CPU rendering because of the visual differences...
Perry
Same. We are CPU all the way, even though i have a halfway decent card in my box. Honestly being able to do both CPU and GPU rendering is not common anymore, most other renderers pick one and devote all their time and effort into it. We all know that CPU is still more stable and reliable (and capable, there are still things that dont work with GPU) but GPU is the new shiny speedy Lambo sitting in the driveway that may or may not get us to the same destination as our trusty Toyota.
To be honest GPU working flawlessly here, rock stable (RTX3080Ti) so it's not a problem at all for me except with older CPU projects but with some small tweaks this can be addressed
Quote from: Furniture_Guy on April 26, 2022, 12:42:16 PM
Unfortunately we have thousands of legacy images rendered in the before time so we must stick with CPU rendering because of the visual differences...
Perry
Also valid. This is a bummer!
I'm ride or die for CPU-- I have an RTX 8000 but Keyshot GPU just isn't stable/reliable enough (often crashes when toggling on/off, verrrrry finnicky with drivers, etc.), and despite the card I do have, scene navigation in GPU is a bit more laggy/sluggish when compared to CPU. I sorta gave up on GPU as a whole, for the time being. Maybe KS 12..
Quote from: hve on April 27, 2022, 06:40:07 AM
To be honest GPU working flawlessly here, rock stable (RTX3080Ti) so it's not a problem at all for me except with older CPU projects but with some small tweaks this can be addressed
And this is the frustrating thing, is that while you have a great setup and workflow, others won't, and there is no easy way to tell why. I think if you have a specific workflow that you don't have to meld with anything else (solo artist, no network rendering, etc) it could be fantastically fast, and I'm super jealous. Its just not there yet. And there are bits missing from the CPU rendering that you can't do in GPU rendering, now that IS getting better and more compatible but I'm not sure it will be a very viable solution for some users. I really wish it would work for me!!!!!
Quote from: mattjgerard on April 27, 2022, 05:59:57 AM
GPU is the new shiny speedy Lambo sitting in the driveway that may or may not get us to the same destination as our trusty Toyota.
Indeed. As I've said here before, faster isn't always better. Sometimes, it's just faster.
Quote from: TGS808 on April 27, 2022, 10:01:26 AM
Quote from: mattjgerard on April 27, 2022, 05:59:57 AM
GPU is the new shiny speedy Lambo sitting in the driveway that may or may not get us to the same destination as our trusty Toyota.
Indeed. As I've said here before, faster isn't always better. Sometimes, it's just faster.
What GPU car are you using, I remember that in onder versions of KS (9 I believe) there where some driver issues, sometimes it's just the driver that is the issue so I'd definitely check that out and see if some versions work better.
Quote from: hve on April 27, 2022, 02:14:00 PM
What GPU car are you using, I remember that in onder versions of KS (9 I believe) there where some driver issues, sometimes it's just the driver that is the issue so I'd definitely check that out and see if some versions work better.
I don't use the GPU at all. No matter the driver you have, at this point the results of the CPU are visually superior to the GPU. That's just a fact. That may change in the future but for now, that's how it is. Now, I'm not saying the CPU is
lightyears better but it is
noticeably better. Certainly enough to make a difference. I use a network of dedicated servers to render so the speed gains of the GPU don't really matter to me. Even if they did, the trade off on final image quality isn't worth it.
Quote from: TGS808 on April 27, 2022, 05:30:14 PM
Quote from: hve on April 27, 2022, 02:14:00 PM
What GPU car are you using, I remember that in onder versions of KS (9 I believe) there where some driver issues, sometimes it's just the driver that is the issue so I'd definitely check that out and see if some versions work better.
I don't use the GPU at all. No matter the driver you have, at this point the results of the CPU are visually superior to the GPU. That's just a fact. That may change in the future but for now, that's how it is. Now, I'm not saying the CPU is lightyears better but it is noticeably better. Certainly enough to make a difference. I use a network of dedicated servers to render so the speed gains of the GPU don't really matter to me. Even if they did, the trade off on final image quality isn't worth it.
Just out of curiosity, based what fact CPU is better then GPU ? Good for you you have accès to network for rendering, for me I'm really happy with the GPU results, they are a bit différent but worse or better just a bit different.
Quote from: hve on April 28, 2022, 03:34:02 AM
Just out of curiosity, based what fact CPU is better then GPU ? Good for you you have accès to network for rendering, for me I'm really happy with the GPU results, they are a bit différent but worse or better just a bit different.
Based on the fact that I've seen the difference with my own eyes. You can search this forum and you'll find it's the case. Even the staff at Luxion will tell you that the GPU and CPU results are not a one to one match. (It's the topic of the thread we are on right now). I'm not telling you not to be happy with your GPU results or not to use it. I didn't say the results of the GPU were bad. I said they are not as good as the CPU and that is true. You say they are "different" and that's fine but those differences are what make it not as good.
Ok thanks for me that's not the case, it's just different and that's absolutely not an issue for me
Quote from: hve on April 28, 2022, 12:07:10 PM
Ok thanks for me that's not the case, it's just different and that's absolutely not an issue for me
I think what's "better" depends on the use-case... for me gpu renderings always flirted with the uncanny valley and just looked like really good computer graphics, less convincing in terms of realism. over time the lines are getting ever more blurred but i think the fundamentals are the same.
if you're rendering something with a very strong anchor in reality and you're trying get the utmost accuracy and make your rendering indistinguishable from real life - then cpu is the right tool for the job.
for marketing/promotional materials "for illustration purposes only" where you may want to have visuals that are "better than real life" - gpu can work for you.
I was just hoping it wouldn't be like that in Keyshot, I was hoping to get the same results just with more accessible hardware..
I've seen what I would call very good results from GPU renderers. Both out of KeyShot and other render engines. That said, in pretty much every conversation/forum posting I can recall about GPU renderers all any one ever talks about is how fast it is and how quickly their image got finished. No one ever talks about how good it is. Speed seems to be the main factor the majority of people are interested in when it comes to GPU. And yes, we'd all like things faster but not at the cost of quality.
Throwing my two cents in, because this is as great discussion.
At this point I'm using 98%+ GPU rendering for almost every project, and have for the past year or so. For animations, it's been a game changer (albeit a buggy, not super reliable game changer).
I agree that CPU has an edge in terms of realism, but even with a 64 core Threadripper, I can iterate much faster on the GPU, which is mind boggling. It's not perfect, but I budget time for a little bit of Photoshop work, and most clients wouldn't know the difference. I can leverage the GPU for rendering lots of images + passes at high resolution, and take advantage of a robust post-processing workflow to take it from 90% to 100%, compared to CPU getting me to 96%.
I agree that "better" definitely depends on the use case. For me, faster can ultimately be better, because it means I can get more revisions in. My goal, however, isn't the same as many of you who are trying to achieve total realism, or to match an existing library of renderings. It's also crazy to think that I haven't rendered on my Threadripper in over a year, it's basically collecting dust. Not what I would have expected when I shelled out $5K for it three years ago.
It's unfortunate that I can't leverage both, and if there was a deal breaking issue with GPU rendering, I wouldn't be able to match the output using my CPU as a backup. To a previous point, it's an "all in" mentality.
I find the discussion interesting - unfortunately, in some cases the differences in the results are even more pronounced than in the example given by the Starter of the thread. We currently see that the GPU simply treats materials and reflections different than the CPU - in the CPU renderings we see effects that were simply not there during scene setup (done in GPU mode).
In the example below you see that in CPU-Mode reflections of the lightning is honored and shadows look completely different than in GPU mode.
Quote from: ddolezal on April 29, 2022, 03:16:33 AM
I find the discussion interesting - unfortunately, in some cases the differences in the results are even more pronounced than in the example given by the Starter of the thread. We currently see that the GPU simply treats materials and reflections different than the CPU - in the CPU renderings we see effects that were simply not there during scene setup (done in GPU mode).
In the example below you see that in CPU-Mode reflections of the lightning is honored and shadows look completely different than in GPU mode.
yes, these differences are pretty extreme and not only a matter of taste.
just a question, are you using
- latest KS Version (11.1.0.46
from 2022.03.21) and
- latest Nvidia driver (512.59 from 2022.4.26)
?
Quote from: ddolezal on April 29, 2022, 03:16:33 AM
In the CPU renderings we see effects that were simply not there during scene setup (done in GPU mode).
Based on what we've known (pretty much) since GPU rendering was introduced to KS, this is not a surprise. If you do your set up using the GPU, you should be planning for a final render using the GPU. If you do your set up using CPU, the CPU needs to be used for final output. Mix and match doesn't work.
Quote from: TGS808 on April 29, 2022, 05:47:40 AM
Mix and match doesn't work.
yeah I understand that this was the case how it works at the beginning of introducing GPU-Mode in KS9 two years ago.
But even at this point of time, Luxion claims in their manual to KS9:
QuoteYou may toggle between GPU and CPU as needed.
QuoteLimitations
The output of GPU mode matches what you get with traditional CPU rendering in KeyShot, with only a few limitations.
- Cutaway material: .../li]
Gem material: ...
NURBS: ...
Legacy textures: ...
Curve geometry: ...
ZSpheres: ...
Volume caustics: ...
Most of these limitations will trigger a warning icon , which will appear in the top right corner of the Real-time View. Click the icon for more information about what parts of the scene are impacted and by what.
https://luxion.atlassian.net/wiki/spaces/K9M/pages/1139015787/GPU+Mode
=> so with this description, with my understanding, both modes should be interchange able (already in KS9, yes we all know this was hardly case...but ok it was a great start!!)
But in April 2022 with KS11.1:
If the modes are not interchangeable, it looks like a bug to me and should be reported to Keyshot.
[/list]
Quote from: mafrieger on April 29, 2022, 06:20:42 AM
But even at this point of time, Luxion claims in their manual to KS9:
QuoteYou may toggle between GPU and CPU as needed.
I haven't read the manual cover to cover and so, haven't seen that. They either need to remove that from the manual or make it true.
Just looked into it:
It's an even enforced claim in KS11
and in addition, named limitations have been reduced:
Quote
The output of GPU mode matches what you get with traditional CPU rendering in KeyShot, with only a few limitations.
- NURBS:...
- Legacy textures: ...
- Curve geometry: ...
- ZSpheres: ...
https://manual.keyshot.com/keyshot11/manual/render-4/gpu-mode/
=> so filing a bug-report for every not matching topic should be very reasonable.
Thanks for everyone doing this, because it makes KS better!!!
Quote from: BoazD on April 28, 2022, 12:31:49 PM
I think what's "better" depends on the use-case... for me gpu renderings always flirted with the uncanny valley and just looked like really good computer graphics, less convincing in terms of realism. over time the lines are getting ever more blurred but i think the fundamentals are the same.
if you're rendering something with a very strong anchor in reality and you're trying get the utmost accuracy and make your rendering indistinguishable from real life - then cpu is the right tool for the job.
for marketing/promotional materials "for illustration purposes only" where you may want to have visuals that are "better than real life" - gpu can work for you.
I was just hoping it wouldn't be like that in Keyshot, I was hoping to get the same results just with more accessible hardware..
Maybe I should change my eyes then, again I see differences but like in other renders (for example try Redshift in C4D vs Physical render and you'll see it's completely different way way different but Redshift is an industry standard like Octane and Arnold and it's a GPU (and now also CPU in Cinema 4D R26) ... again all ok for me but I think he GPU is totally ok for me and is the future for rendering for most of us
Quote from: ddolezal on April 29, 2022, 03:16:33 AM
I find the discussion interesting - unfortunately, in some cases the differences in the results are even more pronounced than in the example given by the Starter of the thread. We currently see that the GPU simply treats materials and reflections different than the CPU - in the CPU renderings we see effects that were simply not there during scene setup (done in GPU mode).
In the example below you see that in CPU-Mode reflections of the lightning is honored and shadows look completely different than in GPU mode.
Strange indeed, some reflections are completely missing, didn't see this in my latest renders but I switched completely to GPU now so I don't compare anymore
Quote from: hve on April 30, 2022, 01:56:52 AM
Quote from: BoazD on April 28, 2022, 12:31:49 PM
I think what's "better" depends on the use-case... for me gpu renderings always flirted with the uncanny valley and just looked like really good computer graphics, less convincing in terms of realism. over time the lines are getting ever more blurred but i think the fundamentals are the same.
if you're rendering something with a very strong anchor in reality and you're trying get the utmost accuracy and make your rendering indistinguishable from real life - then cpu is the right tool for the job.
for marketing/promotional materials "for illustration purposes only" where you may want to have visuals that are "better than real life" - gpu can work for you.
I was just hoping it wouldn't be like that in Keyshot, I was hoping to get the same results just with more accessible hardware..
Maybe I should change my eyes then, again I see differences but like in other renders (for example try Redshift in C4D vs Physical render and you'll see it's completely different way way different but Redshift is an industry standard like Octane and Arnold and it's a GPU (and now also CPU in Cinema 4D R26) ... again all ok for me but I think he GPU is totally ok for me and is the future for rendering for most of us
I'm not saying GPU renders can't look good, or even great... and I acknowledged that over time as the tech improved the lines have blurred between the potential of gpu and cpu, that's just how I've seen things come about.. speaking of Keyshot specifically - i still think cpu is way more convincing in terms of realism and accuracy. again, that isn't to say you can't reach pleasing results on gpu, it just depends what you're after.
I mean, we know keyshot was exclusively a cpu renderer until like 5 minutes ago (exaggeration) and it makes total sense that all the efforts until then went into getting the best results on cpu, and only recently they've been making tweaks to make it work as best they can on gpu. in this context it's unreasonable to expect similar results from both render engines, but then the Luxion marketing department got to work and completely oversold this feature which leads (rightfully so) to user disapointment at best and dare I say a demonstrable case of false advertising (allegedly, not a lawyer, not legal advice or accusation, don't sue me).
Quote from: hve on April 30, 2022, 01:56:52 AM
Maybe I should change my eyes then, again I see differences but like in other renders (for example try Redshift in C4D vs Physical render and you'll see it's completely different way way different but Redshift is an industry standard like Octane and Arnold and it's a GPU (and now also CPU in Cinema 4D R26) ... again all ok for me but I think he GPU is totally ok for me and is the future for rendering for most of us
You like the GPU and get good results from it. We all understand that. You don't have to keep trying to convince us. GPU rendering is definitely not the future of rendering for me (and probably a lot of others) no matter what you think but that's ok. If you're not an Nvidia stockholder, you don't have to sell us on it. Enjoy rendering with your GPU and keep enjoying the results.
Quote from: mafrieger on April 29, 2022, 03:50:39 AM
yes, these differences are pretty extreme and not only a matter of taste.
just a question, are you using
- latest KS Version (11.1.0.46
from 2022.03.21) and
- latest Nvidia driver (512.59 from 2022.4.26)
?
Yes to both questions.
We use 11.1.0.46 and the latest Production driver for our 3080 TI, Which is 511.26.
From our point of view it is a bug - as not only the reflections, but also the shadow areas in the lower left part of the tray look completely different.
It seems that some material properties are simply not honored by the GPU during rendering.
Regards,
Dieter
I did some more tests this times with caustics (something I don't use that much) but I must admit that indeed there's quite a bit of difference in both renders
I'm in jewellery rendering, and I use caustics all the time. At least I try. And I have also noticed a big difference in caustics on GPU/CPU... Also, Spotlight color map seems to have different positions on GPU vs CPU. I'm thinking it is the similar problem as with caustics, it seems like the HDRI position is different, so that is why we're getting different caustics results.
Not sure if this is of any help but I noticed that it's especially an issue with some floor materials in this examples, not all materials have the above issue
Quote from: hve on May 13, 2022, 02:30:43 PM
Not sure if this is of any help but I noticed that it's especially an issue with some floor materials in this examples, not all materials have the above issue
Good point. I think this is part of the issue unfortunately. It's the unpredictability that can be problematic. It's a bit easier when the rules are quite rigid, but when there are some things that work and some that don't... it's hard to keep track of what can be relied on and what can't be.
Quote from: Will Gibbons on May 16, 2022, 07:17:08 AM
Good point. I think this is part of the issue unfortunately. It's the unpredictability that can be problematic. It's a bit easier when the rules are quite rigid, but when there are some things that work and some that don't... it's hard to keep track of what can be relied on and what can't be.
yes indeed Will, now I know of the problem I try to compare more between both renders and there's definitely something going on that's strange
since this seems to be an important topic for many "power" users, would be pretty nice to see some comments from Luxion / Keyshot team...
Could they reproduce this?
Is this on the high prio list?
They are completely different algorithms processed in very different ways. In my experience GPU is not even close to CPU when it comes to visual quality. It is great for animations though.
If you build your materials from scratch using only GPU you can get the look you need. It may not be perfect but it can be done.
I purchased a 3090 purely for this purpose but I always end up back on CPU, because it just looks better.
Quote from: theShopFloor on May 25, 2022, 03:00:08 AM
They are completely different algorithms processed in very different ways. In my experience GPU is not even close to CPU when it comes to visual quality. It is great for animations though.
If you build your materials from scratch using only GPU you can get the look you need. It may not be perfect but it can be done.
I purchased a 3090 purely for this purpose but I always end up back on CPU, because it just looks better.
so basically the marketing claims by Luxion created expectations that drove you to spend a good chunk of change on a high-end GPU that you can rarely utilize. I too am not using the RTX A6000 in my machine as much for rendering because of this reason and I'm sure we're not alone. a lot of people (and businesses) procured expensive hardware and didn't get the results that were promised. this is a very serious issue.
everyone here understands that the algorithms are completely different - I even stated that much in the original post starting this thread. but when a company makes a claim that their software creates physically and optically accurate and realistic true-to-life visuals, using either CPU or GPU interchangeably, then I don't care about the algorithms, I expect a consistent result.
you can solve 3^3 any which way you like but you better reach the same result or else something is broken.
Algorithm 1: 3*3*3
Algorithm 2: 3*(3+3+3)
Algorithm 3: (3^2)*3
I still get 27.
Luxion is making an objective claim. I can't be forgiving about this.
Any news on when a new update might be available ? thanks
KS11.2 GPU related fixes:
Fixed an issue that caused GPU Geometry Setup to take longer than expected.
Fixed GPU issue for advanced materials with fresnel disabled.
Fixed GPU issue for direct lighting for rough materials using bump.
Fixed the issue where GPU crashes when using GPU mode while using measured materials.
Fixed the issue where the GPU mode is disabled after adding geometry to a scene with geometries included.
Fixed an issue where the Reflection Render Passes in GPU mode give black output.
https://manual.keyshot.com/keyshot11/manual/whats-new/release-notes-2/release-notes-11-2/
=> does this improve some things?
After our first tests I can confirm that something definitely happened.
The first scenes we had did not have significant differences, only in "grainyness", but this might be causes by different rendering approaches on CPU and GPU.
From my point this seems to be solved!
Regards,
Dieter
For me both renders GPU and CPU do still look quite different in this new update + now I have a crash here each time I try to select a previously saved workspace, all other presets work fine just one workspace preset seem to cause problems here, will investigate more and see how it works on older projets.
just did a fast overlay: the objekt seems to be ok, but there is something really strange on the groundplane:
Yes indeed the model is ok it's the reflections/caustics that look completely different, I joined the project in my previous message in case.
are there only differences between GPU and CPU, and Keyshot versions or does the GPU driver version also influence the appearance?
@hve
sorry I'm not on latest KS yet.
did you check if there maybe is a very simple inconsistently,
e.g. the switch for enabling/disabling caustics in menu lighting/caustics
doesn't work for GPU so it's maybe stay always en- or disabled,
while it works fine for CPU and influence the result as expected?
I didn't test with older drivers on this new release, I updated my drivers a few days ago testing out omniverse, but the issue looks a lot like in my earlier image posted above so I guess it's related to how Keyshot renders in GPU vs CPU ?
Would be great to have some input on this from Keyshot why there's so much difference on the ground reflections ?
https://forum.keyshot.com/index.php?topic=28832.msg120661#msg120661 (https://forum.keyshot.com/index.php?topic=28832.msg120661#msg120661)
Quote from: hve on May 05, 2022, 07:01:22 AM
I did some more tests this times with caustics (something I don't use that much) but I must admit that indeed there's quite a bit of difference in both renders
Hi hve,
Can you share this scene?
You can send to dries-at-luxion-dot-com.
Dries
Hi Dries here you go, I sent it to email too, thanks, Hans