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Issues with lighting and Reality 2.5
Posted: 22 June 2014 01:23 AM   [ Ignore ]
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I am using Reality 2.5 and LuxRender to render my images and I cannot seem to get the lighting right.

I have an outdoor seen so I added a sun.
When I render the scene I get an efficiency of just over 100% which seems a bit on the low side for a bright day…
When I add a diffuser to get rid of the hard shadows from the sun, the efficiency drops to around 90% and my model is somewhat grainy while the rest of the scene (which is not affected by the diffuser is fine).

After that I tried adding a softbox but I have to crank up the setting to make it affect.
If I change the power to something large like 4k watt my scene isn’t affected although the softbox is really close to my subject.
Only when I change the gain to 10 I see something change in my scene and I get an efficiency of 103%.

I attached an image of the scene that I am trying to render.

The current image has a sun, diffuser and 2 softboxes and both softboxes have a gain of 10 and power output of 4k and efficiency of 57 lumen/watt.

Any pointers on this?

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Posted: 22 June 2014 02:56 AM   [ Ignore ]   [ # 1 ]
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How long are you letting the render run for?  What is the S/px value when you are finished with the render?

You do know that Luxrender doesn’t stop rendering until you tell it to, and that overnight renders are common with Luxrender?

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Posted: 22 June 2014 03:02 AM   [ Ignore ]   [ # 2 ]
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Yesterday I had about 200S/px. I know, not enough but I stopped it because everything else in my scene was nicely rendered without much grain. Except for the model. She was still grainy and because it was running at below 100% efficiency I thought it would never get better.

It’s because I read that if the efficiency is not high enough, LuxRender doesn’t find enough light and you might end up with grainy renders.

I am starting out with Reality and LuxRender and I am scarred I will loose a whole day rendering and and end up with grainy renders smile

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Posted: 22 June 2014 03:08 AM   [ Ignore ]   [ # 3 ]
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I haven’t used Reality or Luxrender for a long time. 

If you wait for a while, I’m sure that someone will be along who can help out more with this.  In the meantime, you could try just rendering the face of the character to see if it will eventually clear.  Save your Scene as it is, start a new Scene, and merge your saved scene into it, and move the Camera forward (or change the focal length) to see if that helps any.  It should render a lot quicker, and you may get to 2000 S/px in a couple of hours or less.

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Posted: 22 June 2014 04:42 AM   [ Ignore ]   [ # 4 ]
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Hi yannic smile I’ve been rendering mostly with Reality for about 2 years now so hopefully I can help tongue laugh

You’ve mentioned the efficiency and s/px value, both of which seem to be on the very low side confused What are your film response, ISO, shutter, and f-stop values?  I’ll be able to better figure things out that way.

As a rule of thumb “less is more” when it comes to using lights in Reality, even for a daylight exterior scene.  People have different preferences; I’ve come to prefer using sIBL for the key and a mesh or softbox for fill and/or eyelight, depending.

It’s a pity the site that hosts the Reality forums is down till the 25th or I’d refer you there; I’ll do what I can to help in the meantime wink

Welcome to your new obsession LOL tongue rolleye

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Posted: 22 June 2014 04:48 AM   [ Ignore ]   [ # 5 ]
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Thanks.
I initially wanted to post this on the Reality forum but as you stated, I noticed it was closed…

My camera in DS has no presets for ISO, shutter and f-stop.
In LuxRender when I use the linear kernel it picks following settings:
ISO 50, 1/1000 and f/5.6

I am also a keen photographer so I understand these settings are normally used in a very well lit environment so I don’t really understand why I get an efficiency of around 90 or just about 100%.

Currently my evironment is setup as you described. I have a sun and a softbox to softer the shadows.

Attached is the progress in my render so far.
370 S/px - 55 kS/s - 117% Eff

It’s been rendering for over 2 hours so far.

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Posted: 22 June 2014 05:25 AM   [ Ignore ]   [ # 6 ]
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It’s great that you have a background in photography; that’s a big advantage when it come to Reality/Lux cheese  I’ve trained and worked as a cinematographer, back when celluloid was still being used raspberry

The camera film settings are done in Reality, not Daz; you’ll still need Daz to set the focus if you want a shallow dof, though tongue wink

RL camera settings aren’t always the equivalent in Reality/Lux; it took me some time to wrap my head around that red face

From what I see, the first and second scenes have good key/fill ratio although they are rather grainy.  Graininess is caused by “light starvation” as Paolo would put it.  A quick and easy fix (and this may seem counter-intuitive) is to tweak the settings while rendering.  That’s one of the advantages of LuxRender:  you can do that without ruining the render.  When the image seems overexposed as you open up the ISO, don’t panic; you can tweak down again when you get rid of the graininess.

I just checked a previous render which is also a daylight exterior scene, it’s eff is 107%; daylight exteriors tend to have low efficiency because the light travels a long distance before bouncing back to the lens.  Low efficiency is not always a bad thing just as high efficiency is not always good (like when a scene is overlight and the RAM usage goes through the roof shut eye )

My suggestion, like JimmyC’s is to create as safety file (and don’t forget to change the file name and output in Reality!) , render in Lux and tweak the settings as it renders.  By way of comparison my daylight exterior settings are:

Film Response: Agfacolor Vista 800 (doesn’t over saturate the colors; kodak favors reds and yellows and fuji blues and greens, like in rl tongue rolleye )

ISO: 1250
Shutter: 1/8
f-stop: 2

In the safety render, I suggest tweaking the ISO up while bringing the Shutter and f-stop down.  While rendering you can have it a bit overexposed and bring it down later by stopping down and/or tweaking the gain (both of which can be done during rendering as well).

I think bringing up the ISO and bringing down the shutter/f-stop should help with the exposure/graininess.

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Posted: 22 June 2014 05:35 AM   [ Ignore ]   [ # 7 ]
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By the way, the eyes look a little cloudy; try setting the material to Glass, removing all the maps, check “Architectural”, set Index of refraction at 1.04, move the thin film thickness and thin film IOR to 0 and set opacity to 1.0.  You should get better results.

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Posted: 22 June 2014 05:46 AM   [ Ignore ]   [ # 8 ]
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THanks for the tip.
I didn’t know I could tweak the gain from my lighting while rendering. This is great. I lost so much time in stopping my render and just tweaking the light gain… Doh.

Increasing the ISO seems counter intuitive to get rid of grain…
I just set the ISO to 400, f/16 and 1/1000 shutter.
I don’t see much difference when it comes to grain.

I am currently at 570 S/px
Will the grain go away if I let it render to up to 1000 S/px or won’t it get better?

It’s strange that only my model is grainy. If you look at the background, especially the leaves in the water, they already look crisp to me.

Thanks for the eye tip. I will try this out on a different render cycle smile

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Posted: 22 June 2014 06:16 AM   [ Ignore ]   [ # 9 ]
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yannick.ongena - 22 June 2014 05:46 AM

THanks for the tip.
I didn’t know I could tweak the gain from my lighting while rendering. This is great. I lost so much time in stopping my render and just tweaking the light gain… Doh.

Increasing the ISO seems counter intuitive to get rid of grain…
I just set the ISO to 400, f/16 and 1/1000 shutter.
I don’t see much difference when it comes to grain.

I am currently at 570 S/px
Will the grain go away if I let it render to up to 1000 S/px or won’t it get better?

It’s strange that only my model is grainy. If you look at the background, especially the leaves in the water, they already look crisp to me.

Thanks for the eye tip. I will try this out on a different render cycle smile

You’re very welcome.  It’s a learning process; I don’t remember how long it was before I realized that I could tweak the settings during rendering tongue laugh

I don’t think the grain will go away, not with your current settings (I’ve had renders that have reached 25K-30K s/px LOL  and yes, they were daylight exteriors).  Tweaking the ISO in Lux is adjusting the lighting in fine increments; while it may seem like a lot, bringing the ISO from 50 to 400 won’t appreciably change the light starvation, especially since you’ve stopped down from f/5.6 to f/16.  Any light that would have come through by upping the ISO would have been negated by the “aperture” getting smaller.

Conceivably those settings could work if you let it render to 5k. Alternatively, let more light in during the render and when the grain disappears stop down.

Beginners ask is there any way to speed up the rendering time, the short answer is “no”, if you want a good render.  The long answer is “yes but only if you use network rendering” but that’s another story raspberry

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Posted: 22 June 2014 06:23 AM   [ Ignore ]   [ # 10 ]
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See if I get this right…

During rendering I should crank up the ISO to something like 800 or higher?
After it has been rendering for a while I can stop it down to a normal value like 200 and this would solve the grainy pictures?
If not, I don’t think I understand how to solve the grain.

I will speed up the process later, I have 3 high end laptops that I will configure as my personal LuxRender farm wink

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Posted: 22 June 2014 07:14 AM   [ Ignore ]   [ # 11 ]
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My recommendation is to bring up the ISO and lower the f/stop.  Most likely it will look overexposed.  That will actually address the graininess because now the image is getting enough light.  Or you can just lower the f/stop till the hot spots look 1-2 stops overexposed.  Let it bake till it looks good then you can tweak the settings. 

I hope all of this this makes sense smile

And it’s great that you have the hardware for a render farm; that will cut down the render time cheese  I use 4 machines with i7 processors and the 32 core total is a huge help tongue rolleye

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Posted: 22 June 2014 08:13 AM   [ Ignore ]   [ # 12 ]
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Thanks for all the help and useful info.
I learned a lot from this thread smile

I stopped the rendering after a little over 5 hours 30 minutes and got just below 1000 S/px.
For the last 90 or so minutes I followed your advise and let it capture light in a slightly overexposed setting.
I didn’t really know that those settings would change the actual render. I thought they were just for visual inspection of the rendering. Because of this, it makes much more sense to play with these settings during rendering.

Here’s the result and I am actually quite pleased with it. It’s so much better than the rendered from Daz3D itself smile

I’ll start another rendering in bit and will keep the advice in mind. I will also try to get better eyes.

Do you have any tips to increase the realism on the skin? I seem to notice that Reality 2.5 doesn’t do a good job in translating the skin material from Victoria 6 (or any 6 model) to Lux so I guess I need to do some tweaking there as well.

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Posted: 22 June 2014 08:38 AM   [ Ignore ]   [ # 13 ]
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W00t grin  That’s pretty good cheese

It’s a PITA the site’s down; there are threads on the best settings for hair and eyes in Reality confused Hair is one of the big issues; there are Do’s that work and a number that don’t shut eye

Thanks for the watch, btw wink

Reality does skin well, actually:  this article really helped.  But in addition to that, make sure to use specular maps; that’s when I started seeing the “poetry of flesh” smile

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Posted: 22 June 2014 08:42 AM   [ Ignore ]   [ # 14 ]
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yannick.ongena - 22 June 2014 08:13 AM

Do you have any tips to increase the realism on the skin? I seem to notice that Reality 2.5 doesn’t do a good job in translating the skin material from Victoria 6 (or any 6 model) to Lux so I guess I need to do some tweaking there as well.

This is Michael 6 HD with Gen 6 skin; at that point I still hadn’t gotten the hang of the eyes downer

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Posted: 22 June 2014 08:52 AM   [ Ignore ]   [ # 15 ]
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holy…. This is really nice.
Is this the default skin or did you apply a different skin? I don’t seem to get similar details in my Victoria 6 skin. WHen I render it seems plastic and without much tone differences.

I still have a lot to learn wink

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