More Nodes and QMC tests

[thomas]

Hi there!

I'm really enjoying myself learning more about nodes and QMC, thanks to Janusz excellent tutorials - and Kray of course! Here's a raw render of my work-in-progress test scene. Plenty of work to do: lots of textures are in "basic" form, not nicely aligned etc... I'm in the process of filling my 3D scene with good-enough objects and surfaces, and then I'm going to do close-up work with photographic references to put some polish on it.

EDIT: added second render.

[Janusz Biela]

Fast hints for you:

1. Forget Area Light from Lightwave (I "see" them in windows holes): ugly, noisy, slow. When use QMC you do not need them - except some situation with lamps. You must wait for K3 where Area Light and LEM has special engine inside Kray not only simulation from Lightwave.
Anyway you see ugly vertical line shadows on the wall coming from windows holes and horrible "interference" near paints.
Here example from Corona which is exactly in K3:

2. There is no "live" in scene but this comes from quality of light and tone mapping. maybe generally brighter with better light shadows (LEM panels instead Area Lights)

[Keraressi Abdelkarim]

can u put ur referance pls ! let give us chance to try it. re model it and try to get realsitic as possible thnx . by the way good start good luck for reste man

[thomas]

Hi Janusz and Lightwave3d!

Thanks for the reply! Regarding your comments:

1) Area lights slow, noisy and ugly: Yes, I agree! I was hoping to get some tips on how to increase the lights quality (I thought I could augment the sampling rays of area lights in the "quality" tab, maybe), but it's good to know I'm better off with luminous polys. Two remarks though: I don't mind the vertical lines in the shadows in the corners of the room, since these are actually fairly natural in these spots, when you have two main rectangular windows. It may seem strange, but in these renders I am not trying to make the most beautiful image, with the most beautiful lighting. I'm mainly trying to get a natural light distribution (given the setup which is a bit artificial), good contact shadows and material surfacing. And remark 2: what do mean when you say "interference" near paints?

2) Little life in the image: Very true, but once again, I don't really mind at this point. My light setup resembles a very overcast day at the moment, with two huge "softboxes" as the only light source, so it's only logical that the light quality resembles that of a day with cloudy, gray weather . When the primary surfacing and modeling is done I'm going to methodically "upgrade" the lighting atmosphere, from flat white to gradient of sky blue with a more defined light source and direction, and finally with summery sunlight entering the room.

3) Lightwave3d: I don't have any reference for the room I'm doing. It's all just going off my imagination. For the furniture, it is all from the dimensiva website (check it out if you haven't already), so once the room is done in first-attempt materials, I'm going to do close-ups using photographs of the furniture to go in-depth in nodes.

As always, thanks for the feedback!

[thomas]

I just replaced the area lights with luminous polygons, and yes, it does look a LOT better already - thanks a lot for the tip! Unfortunately I only have a tiny and slow laptop at home during the weekends so no good renders to post! I'll do some high-res shots on monday when I have access to my workstation.

[thomas]

Alright, here's my progress! This is a raw render using LEM instead of area lights. For settings I just used the medium preset, turned off cache irradiance and set anti-aliasing to low. I know that for final renders I'll need to use different settings and render a double resolution. That will help with the noise.

Also, Janusz, I have to admit it looks much better without the vertical shadow lines in the corner!

But!!! What the hell is happening in the corner, in the vertical line on the right hands side of the image! I'm getting ugly photon artifacts here. As far as I know my model is done correctly here. Any ideas on how to fix this? It's probably a bad idea to use the standard medium settings, but where should I make the changes best? GI resolution?

As always, thanks for the help! I appreciate it!

edit: Added second image. Same situation here: still noisy but better shadows than with area light, but here as well splotchy photon distribution in the corner on the right hand side of the image.
edit2: Added couch image, just for fun. A lot of work to do here, I know. Add carpet. Make black seats less plastic and more leather. Fix polygon error on seats. Surfacing on table better. Fabric on couch a lot better. Set dressing in general.

[Janusz Biela]

Everything is ok. This "strange" behavior in corner comes from Photon Map Cells which takes information from outside - cells has "physical" size as interpolated simulation of real photons. This is normal and common everywhere and to correct errors, render engine must shoot extra Path Tracing photons. In Kray this correction tool is in FG tab called: Path Passes. Is enough to shoot one bounce light Path Tracing photons with 50% distance from corner:

Path_Passes.png (3.8 KiB) Viewed 10009 times

[thomas]

Alright, thanks for the tip! Slowly but surely I'm learning what each button or option in Kray does!

Here's my latest render, using Path Pass 1 / 50% (which does work great), at double HD and with some colour grading and a very mild DOF.

[Janusz Biela]

This looks good. Now you can add Power Shader for LEM light in window:

plus Kelvin colour scale for this light:

[thomas]

Hi all, and hi Janusz!

Here's a new raw render, HD straigth out of Kray without post.

I did what you mentioned, but I have some questions.
1) About the colour: the Kelvin value just get converted into RGB values, right? I changed it as you said, into 7720 Kelvin. Very slightly more blue overall, but the change is so subtle that it gets lost in the colour grading. My previous colour was 235 / 245 / 255. Your Kelvin colour is 231 / 236 / 255. Not that big of a change, but it looks nice!

2) About the photon multiplier. I set this to luminosity to 4. It was a bit too bright, so I lowered the surface luminosity from 250 to 200. Can I ask what the reason is for the photon multiplier? From what I understand, it is to increase the light in the scene without creating overblown reflections in some surface. Or is there another reason to use it here?

3) Just a remark: I set the candle holder surface to double sided because there was a weird reflection showing up on the inside. Better now!

Thanks for all the help so far. Very little time this week, but I'm going to do a lot more work during the weekend to show here. Damn, Kray is fun (and powerful).

[Janusz Biela]

This Kelvin scale is just example (of course should be more blue) and is better use Kelvin colour scale then setup sky colour from a hand. Better idea is to use Physky plugin but in Kray this system is old. Situation will change dramatically with Physky2 in Kray 3 where simulation is much better, gradient more realistic.

Photon Multiplier make just stronger photons. By this effect we increase "bounce life strength". It is also kind of tone map build inside photons - so tool give more flexibility with light setting. Of course everything has good limits and for this tool usable ranch is maximum 2-4. Over that we start bend realism. Increasing Power we must decrease luminosity.

Double reflection is not supported by Kray - only simulation from Nodes...better then nothing.

As you see scene get more life and has now correct bright balance. Window area should be not over bright with visible window frames.

[thomas]

Hi Janusz,

Alright, it's interesting to hear this effect of photon multiplier, increasing bounce life strength. Great tip, and good to know I need to stay between 2-4 range. And yes, it gives more life to the scene. Great tip as usual.

I did not mean double reflections, but just using doubled side polygons on the candle holder because there was a render error in it - if you look at my first renders you'll see that one of the candle holders on the table has an impossible reflection on it.

More renders coming up in the next few days! I'm having fun!

[nico]

THOMAS!!! good render, very realistic! where is Janusz's tutorial?

[Janusz Biela]

THOMAS!!! good render, very realistic! where is Janusz's tutorial?

Maybe today will upload scene - is almost ready.

[thomas]

Actually, Nico, Janusz has been so nice to put tutorials all over the Kray forum!

I would say:
1) Start by going over his Node surfacing tutorials part 1 and 2.
2) Turn off cache irradiance and get a feel for this.
3) Show your test renders and ask for advice!

Oh and, thanks for the compliment!