Strange iRay Differences 4.9.2 vs. 4.9.4
AndyS
Posts: 1,438
Hi,
as the new iRay addon for the West Park assets appeared, I thought to compare with my own iRay adaption which I already created as iRay appeared in the DAZ universe.
But then some strange effects happened.
As often proposed I used the "Architectural Sampler" to speed-up the render of the the interior scene. In DAZ 4.9.2 this worked perfectly and saved round 25% rendertime for interior scenes with large indirectly lighted areas.
1. Nowadays I use DAZ 4.9.4 Beta. But suddenly, at about iteration #40 the render started to dramatically overlight (more than 3 EVs). Without using the architectural sampler (filter) I got the normal result shown in the attachment. Environment is Sun-Sky and tonemapping at 1/125s, 1:8, 100 ASA, Gamma: 2.5 with contrast 1.15
The water on the floor is produced by simply using an additional topcoat setting. Also for a long time my own shader setting.
2. As a reference I transferred the complete scene back into DAZ 4.9.2. Here I experienced that all the indirectly lighted areas rendered way darker - way too dark - compared to DAZ 4.9.4. As we know, the scenefile includes the complete render settings. And indeed: Lighting, environment settings, tonemapping, etc. are all the same settings. But I got this totally different outcome!
I really don't have any clue why there is this difference in the versions.
Did somebody else experience such strange effects?
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Comments
What are your specs? PC or Mac what OS? Which drivers for your Nvidia video card what are you using to cool your video card air or liquid? Oh are you using CPU or which version of Nvidia video card and is it jumping to cpu mode? Not enough information to make a suggestion.
Oops,
why does it depend on the environment (hardware), that there is that dramatically change in the render engine's behaviour?
But to satisfy your curiosity: I only could allow myself the most primitive setup.
Perhaps with the updated Iray renderer, you no longer need the Architectural sampler for this situation.
We know nVidia have been messing with sampling priorities to achieve convergence quicker, perhaps this improved sampling has also led to better dark region resolution.
Just asked because If you are on a laptop you could be cooking your laptop if you are Iray rendering with built in Nvidia card and this might be causing problems with renders. The temperature profiles for built in Video for laptops are OK for gaming but Iray can cook your laptop. If you are on a desktop you need to turn the video card fan to 100% before rendering Iray otherwise you will cook your video card. If you are using newer Nvidia drivers people have been reporting problems with Nvidia changing stuff in CUDA. If you are on Windows 10 people have been reporting problems with this OS and Daz studio and Iray.
So this only demonstrates:
nVidia simply added new bugs in every new version (instead of solving the old ones) and a lot of arguments that iRay at the current state is not a valid addon for DAZ.
And pardon:
before your activity starts to cook your graphic card or even your laptop, the operating system and at least the bios of the motherboard stops the system. The serious ones !
But anyhow an overheating never causes the observed changes.
You get different outcomes because Iray is being actively developed and changes are being made to it. When it was first released in Daz Studio, skin tones had to have a bluish tint on a channel to appear correctly hued. The Architectural render option received some improvements and does now support light portals IIRC.
It's a bit of a challenge because the options and interface remain unchanged from one version to the next, but things work somewhat differently. Reading the announcement post thoroughly is essential to leverage the new versions at your best.
Pay attention to the Crush Blacks setting in the tone mapping, lowering it will make your dark spots more detailed but will also increase render times. I would rather increase the Ambient Strength to a point where the dark spots are exposed as I want and then adjust the Burn Highlights slider. Remember that for a quick adjustment you should double or half the values anytime you adjust: Ambient Strength should go 1, 2, 4, 8, 16... or 1/2, 1/4, etc.
About the Iray engine being an intensive task, that's certainly true, but since nVidia cards come with thermal management, they will reduce their frequency in order to avoid artifacts or heat damage. As long as you don't mess with your card parameters via AfterBurner or similar software you are safe. If you decide to tweak, the best policy for raw performance allows the fan speed to increase to 100% before the card lowers the set clockspeed. But I got pair of reference 980Ti and at 1380MHz (+200 offset) they don't go past 80% fan speed at 76°C. Leaving the fan at 100% all the time is just too loud and will kill your fans in a short time, not ideal since a fan is usually already short lived compared to a chip.
You get different outcomes because Iray is being actively developed and changes are being made to it. When it was first released in Daz Studio, skin tones had to have a bluish tint on a channel to appear correctly hued. The Architectural render option received some improvements and does now support light portals IIRC. Pay attention to the Crush Blacks setting in the tone mapping, lowering it will make your dark spots more detailed but will also increase render times. I would rather increase the Ambient Strength to a point where the dark spots are exposed as I want and then adjust the Burn Highlights slider. Remember that for a quick adjustment you should double or half the values anytime you adjust: Ambient Strength should go 1, 2, 4, 8, 16... or 1/2, 1/4, etc.
It's a bit of a challenge because the options and interface remain unchanged from one version to the next, but things work somewhat differently. Reading the announcement post thoroughly is essential to leverage the new versions at your best.
About the Iray engine being an intensive task, that's certainly true, but since nVidia cards come with thermal management, they will reduce their frequency in order to avoid artifacts or heat damage. As long as you don't mess with your card parameters via AfterBurner or similar software you are safe. If you decide to tweak, the best policy for raw performance allows the fan speed to increase to 100% before the card lowers the set clockspeed. But I got pair of reference 980Ti and at 1380MHz (+200 offset) they don't go past 80% fan speed at 76°C. Leaving the fan at 100% all the time is just too loud and will kill your fans in a short time, not ideal since a fan is usually already short lived compared to a chip.
Hi GLE,
imagine you created a lot of scenes. And suddenly with the new DAZ release the lighting doesn't work anymore, respectively produces a desastrous result.
I think, every user would be annoyed.
I as a software architect would never include an additional software into my project, as long as this software is not in a stable state.
To the other argument, overheating would have caused the very different result:
I never heard that this would cause a program executable to calculate completely different.
And btw: As already stated: I can only work CPU-only. ;)
Software evolves and sometimes chnages happen that alter how things work because the old way was actually broken. I remember a big hullabaloo over changes made in City of Heroes during the close beta of City of Villains for exactly this particular case.
Just read in the notes for the 4.10 beta, the Architectural Sampler is deprecated and will be removed in Iray 2017.1.
Thank's for the news.
So I don't care about this bug anymore.