Starting on QMC and nodes

[thomas]

Hi all (and hi Janusz )

I'm diving into sort of physically accurate nodes and qmc, and am ready te learn, so all suggestions are welcome!

Here's my first test render and setup info (render settings and computer info). Raw, no post.

A have a couple of quick questions:
1) What do you think of the render time? As the info below says: 22 minutes on an i7 at 4 Ghz, with 16 GB ram. Windows 10. Full HD resolution. Giving the simple nature I would think it should be able to go lower, but I haven't had any success there.
2) Noise: I'm using 100-800 samples. Going higher seems to be overkill. Is the current level acceptable to go into post (and denoise in Photoshop or other), or should I be able to get it lower in the raw image.
3) Any other general comments to help me progress?

Cheers!
Thomas

[thomas]

Also, just for info: I've created my materials based on Janusz excellent tutorials on physically accurate nodes. Cool stuff, a lot simpler than I thought, and I have to say that just using the colour tool node is worth gold!!! So for all people that are holding off on using node-based materials, I have to say: go for it!

[Janusz Biela]

QMC render system has no interpolated sampling (similar to Path Tracing) but Photon Map is interpolated so QMC is something between Final Gathering and pure Path Tracing. In my opinion this is the best solution now for rendering at all. Differences between pure Path Tracing and QMC based on Photon Map is slightly small (amateur cannot recognize differences). Important is only one thing: very good Photon Map solution.
Best idea is when Photon Map solution is based on Interpolated Path Tracing photons (in Kray exist that option called Path Tracing Cached since the beginning of K2). Apparently in Kray do not exist mix of Path Tracing Cached Photons with QMC render sampling (it will be in K3 so this will be something similar to Corona Render). But still me and G. we have hopes for ultra-modern Final Gathering K3 render. It can be chance when this new engine will receive quality of QMC sampling. I do not need explain how it means for time render and quality without noise.

Time of render with QMC system is around 2-4 times longer than Final Gathering (depends how less noise we want or how much visible) but in Kray this part of engine is quite fast and can surprise. Real deal with QMC comes with HiRes rendering: more pixels less noise. A4 or A3 format is very profitable to use and from experience the time render is same like Final Gathering but quality far better. Also with higher resolution we can go down with QMC quality in settings! Rendering panorama images (8000pix/4000pix minimum) has only sense with QMC rendering.

Also very good idea for really high quality renders is re-scaling (very popular in Octane, Maxwell, etc). This is basic idea based on HiRes rendering with low sampling quality and AA solution. After we get ugly and noisy render RAW material which is really good for post processing: de-nosier and re-scale down for perfect AA.

I will upload soon scene with settings for low res and Hires because in your setting is a lot to change so better when I upload ready solution for all situations.

[thomas]

Hi Janusz,

Thanks for the reply and the info! I'm sure there is a possibility to create super-quality renders with final gathering, with an updated render engine (like Kray 3!). I tried to increase the number of samples in final gathering to very high to save time, but unfortunately I kept getting an ugly light leak where the concrete wall meets the ceiling, no matter how high the settings.

I wonder how you will improve on my settings - don't misunderstand me, I'm sure that you will be able to improve my settings a lot, but I am curious to see how, because I think that my photon map is okay for this use, but qmc still gives me plenty of noise.

I'm currently testing rendering at double resolution - I'm sure this will help with DOF-effects as well in cleaning up edge/depth artifacts.

p.s. It's cool that I'm finally starting to understand some of the Kray and nodes settings. I was one of those guys that only used the low and medium presets

[Janusz Biela]

Final Gathering in K2 has a lot issues (of course still one of the best but need to be update). Problem is not with sampling but with Photon Mapping: sampling is based on information from Photons - why K3 has new PM engine. Automatically Final Gathering (also Path Tracing or QMC) are much faster in K3 with new Photon engine also G. promised write new Final Gathering.

I wait for correct working Physky2 in K2 (appears small issue with virtual extra light in scenes ) and working PhotonMap from all light sources (photons are shoot from light sources and this affect really high accuracy but still not working from Physky)


Sadly we do not have yet ready KrayShader - without this rendering has no sense because good GI is not only one aspect of good rendering. Nodes helps only partly by this what you mentioned: texture processing.
Actually, the node texture processing is very strong point of Lightwave: reach and flexible system...is really there nothing missing.

[Janusz Biela]

...I did not forget scene. Almost ready - prepare details need sometimes extra time.

[thomas]

Hi Janusz! Wow, thanks very much, I appreciate the help!

I'm already working on a second scene - a lot bigger, more surfaces and more details, and doing tests on how I can render at double resolution and scale down. I'll show it here in a couple of days!

[Janusz Biela]

Here scene with all examples.

[nico]

yeah!!!

[thomas]

Hey Janusz,

Another question: do you use the fresnel angle, or better said, the reflection output from the fresnel shader or your curves as input for the number of samples in the reflection shader? I was just thinking that might be a way to render faster - since low reflection values would lead to lower noise they don't need as many samples as high reflection values (at glancing angles).

[Janusz Biela]

Hey Janusz,

Another question: do you use the fresnel angle, or better said, the reflection output from the fresnel shader or your curves as input for the number of samples in the reflection shader? I was just thinking that might be a way to render faster - since low reflection values would lead to lower noise they don't need as many samples as high reflection values (at glancing angles).

I think there is no way to control this in Nodes. Reflection effect is calculated in Kray Engine. We can only limited reflection bounces.