Render-Time Issue because of Skin Shader & Water Shader

Rhian-Skyblade

I am hitting currently a massive wall with my render time.

I am currently working on a few Indoor Scenes that give me a massive headache because they need an awful huge amount of time to render as soon as the process hits on skin and water. It takes almost 2 minutes per pixel to render.

The scene I am doing now contains the same Skin Shaders, the same water, the same Render settings I used in previous scenes that rendered much much much faster.

Details of my current scene:
Skin Shader: Delphinia Carrara Shader (with blurry Reflection but no subsurface scattering) as Base - with my own textures.
Water Shader: what comes with Darkwald
Lights: Distant 30 % no Shadows (excludes Characters), 4 X Bulbs with Soft Shadow "Fast", and one Spot Light 70 % only for my characters no Soft Shadows.
Objects: 124 Master Objects - though these render pretty fast.
Resolution: 2100 X 1350
Quality: Tried 140 DPI and 90 DPI - no real change in time
Render Settings: Full Ray Tracing with Shadows, Reflections, Refractions, Light Through Transparency, Transparency...
0,5 for Shadows and Detail
No ambient occlusion.... just the lights I mentioned before.

12 GB RAM, Intel Hexacore 3,33 GHz Extreme and loads of Harddrive Space...

A few weeks ago I did this scene and it rendered in almost no time - like 3 hours + give or take a few minutes.
Warning - slightly mature content: http://www.deviantart.com/art/Blackreach-381365660

(rendered in 2100 X 1350 - reduced in Postwork to 1800 X 1240)
Full Raytracing and everything checked except for Shadow Compatibility and Gamma Correction,
Further Settings: Best Antialiasing, 0,5 for Shadow and Detail
No Ambient Occlusion - just the lights that come with Darkwald + one single Spotlight only directed at the two characters in that image.
So I am quite at a loss here what I am doing wrong in my latest scenes....

What have I tried so far?
I took soft shadow away - didn't really help - same slow progress as soon as the render process hit the skin and the water

It must have something to do with the skin reflection and water reflection...
Only if I remove the reflection from the shader it renders faster - but then the skin looks dull and flat. No sheen.

I played with the reflection - took away the blurry reflections on water. Did not really help and also looked pretty crappy.
I turned off subsurface scattering for water, did not help either.

I even tried to reduce the reflection - didn't really change anything about the render time.

I took away the reflection on the skin and tried to go with Highlight 0 - Shiny 100 on Skin Map
Skin still looked dull and flat, sheen was gone which I do not understand. I used the Skin Maps that were made for the shiny highlight effect.

In a Tutorial video I saw someone "faking" skin reflection by setting Highlight to 0 and playing with cellular in "Shiny" and it worked well - seems not to work for skin maps.

Any Hints what else I could try?
As I said... the scene I posted the link here worked pretty well and rendered pretty fast.
The scenes I am doing now use the same setup and water and are even somewhat smaller and contain far less items.

Headwax

Hmm, sorry I can't see your example as my mature content filter is on by default?

Let's see, these are the things that slow me down.

Refraction, subsurface scattering, reflection. soft shadows.

So what you could try I check with the water that there is no refraction.
You can fake the reflection but putting a texture map In the glow channel.
So the go would be to isolate things one at a time and do a spot render and see what happens.
The same thing goes with the lights.
Just turn all your lights off and do a spot render and watch what happens.
Then turn them on one by one and do a spot render.
This will tell you if one of your lights is the culprit etc.....

IE just take out one parameter at a time and you will see where your slowdown is.
Oh I only render on good aa, never best

Rhian-Skyblade

Hi Head Wax

yep, deviantArt considers that piece of work mature and you can only see it if you have an account and can login :-(

Try this - posted it also on Renderosity - just a bit smaller in resolution.
http://www.renderosity.com/mod/gallery/index.php?image_id=2452187

I already tried to take away the lights.
Only had in the end the Distand Light active - that one has "no" shadows at all. Didn't really help the skin and water issue.

My guess is, something with the reflections is not right - on both of skin and water.
As I said. When I did Blackreach it rendered in no time and there I had highest quality and full reflection...

I tried to render my new scenes without reflection, then it renders a tiddy bit faster but looks horrible.
Weird enough - even with reflections in the render settings turned off - the skin has a nice sheen. As soon as I remove the reflection maps, the sheen is gone *makes a face* Highlight and Shining get ignored.

Question is, can I post the shader setup of the Darkwald Water and the Skin Shader as soon as I am back home this afternoon (in about 6 hours) or would that violate something and give away secrets only one who has bought the product should know.

The joke is - the Darkwald scene had far more to reflect and all that than my current scenes :-/

Headwax

ha ha well I can see why it is adult content,
beautiful render!
well I don't have the scene I am sorry, I have afew of Howi'es things because I try and support carrara pa.s but they are not usable for me because of the render times

oh it looks like there are things in the glow channel of the shader?
maybe there is also a scene filter like aura etc set? but I think they ( the scene filter) are post render effects so maybe wouldn't slow you down the way you are finding.

are their textures in the highlight channel?
someone told me Howie uses subsurface in his leaves so maybe that is happening with the mushies?

sorry I am no help

Rhian-Skyblade

Nah. That scene you looked at rendered very fast. No joke. Maybe 3 hours or so. Took me longer to set it up ^^
The glowing effect didn't really do much either. Used it only scarecly in this scene.

My current scenes do not really have anything fancy like that. No glowing - besides the candle-bulb glow but even if removed it is slow with skin and water.
I even took away everything except for water and characters... and well, the render time gets awful here.

It's really only the water and the skin.

The Body Maps (they look a little darker than the bump maps with highlighted zones) were previously in the Highlight Channel. But I switched them into the Shining/Shiny channel in the hope to live without the blurry reflection on the skin. But it doesn't really matter if I have them in either channel. No reflection results in an ugly skin effect :-/

ringo monfort

Rhiana said:

Nah. That scene you looked at rendered very fast. No joke. Maybe 3 hours or so. Took me longer to set it up ^^
The glowing effect didn't really do much either. Used it only scarecly in this scene.

My current scenes do not really have anything fancy like that. No glowing - besides the candle-bulb glow but even if removed it is slow with skin and water.
I even took away everything except for water and characters... and well, the render time gets awful here.

It's really only the water and the skin.

The Body Maps (they look a little darker than the bump maps with highlighted zones) were previously in the Highlight Channel. But I switched them into the Shining/Shiny channel in the hope to live without the blurry reflection on the skin. But it doesn't really matter if I have them in either channel. No reflection results in an ugly skin effect :-/

Blurry reflections take a very long time to render. Someone recommended to use a blurry texture map and set the reflections to very low this will give you similar effect as blurry reflections but the render time will be faster.

Rhian-Skyblade

Thank you Ringo,

I am trying to go by that :)
made the texture blurry in Photoshop and in a few moments I know if it looks OK.

I also found out now my mistake with the highlight and shining...
When using texture maps, its the other way around as if I use celluar patterns for the sheen effect.
With Maps, I need to place them in highlight and set shiny at 0...

Jonstark

I can tell you right now that it's the blurry reflections that's killing you; Ringo is absolutely right.

One trick that I think DimensionTheory suggested a good while back (before the forums became so hard to use) is to take a specular map of a character, use photoshop to blur it, then use it as a reflection map with a multiplier operator with a very low percentage (2 or 3 percent max) and you can get similar results without having to have blurry reflections checked. Most skin also looks better with a slight bit of SSS, in my opinion, but since your scene has characters with very dark bluish skin I can see that you might not need that in this instance, and the specular effect is more important by far.

Personally though, I don't see a lot of difference/gain in using reflections at all. I think you can get a very realistic skin effect just by tuning the highlight/shininess channels. And if you don't use the reflection channel, it also improves rendering time. If you use a multiplier operator and a color (like blue, to mimic the shades of reflections you'd get from the glowing blue mushrooms) I think you can get the same effect using highlight and shininess and avoid reflections at all.

You will need reflections in the water, but I really don't think you need blurry reflections there at all; the ripples in the water should be more than enough to break up the reflections realistically.

Really pretty scene; nice work. Also very adult, so those who are clicking the link be warned :)

Rhian-Skyblade

Jonstark said:

I can tell you right now that it's the blurry reflections that's killing you; Ringo is absolutely right.

One trick that I think DimensionTheory suggested a good while back (before the forums became so hard to use) is to take a specular map of a character, use photoshop to blur it, then use it as a reflection map with a multiplier operator with a very low percentage (2 or 3 percent max) and you can get similar results without having to have blurry reflections checked. Most skin also looks better with a slight bit of SSS, in my opinion, but since your scene has characters with very dark bluish skin I can see that you might not need that in this instance, and the specular effect is more important by far.

Personally though, I don't see a lot of difference/gain in using reflections at all. I think you can get a very realistic skin effect just by tuning the highlight/shininess channels. And if you don't use the reflection channel, it also improves rendering time. If you use a multiplier operator and a color (like blue, to mimic the shades of reflections you'd get from the glowing blue mushrooms) I think you can get the same effect using highlight and shininess and avoid reflections at all.

You will need reflections in the water, but I really don't think you need blurry reflections there at all; the ripples in the water should be more than enough to break up the reflections realistically.

Really pretty scene; nice work. Also very adult, so those who are clicking the link be warned :)

Thank you for the compliment on that scene :) was fun to play with Darkwald a lot. I think I will use that setting more often, though with different colors.

As for the reflections. You are so right.
I tried the blurry map and wasn't happy. It was fast... but now I am using shine/highlight and that looks much better on such dark skin.

I usually try to stay away from SSS when water is involved. Had once a try on my water dragon... and it was horrible. I counted almost 5 minutes per pixel in the "normal" water reflection and I had nothing fancy activated. Only simple reflection and as you said - through the ripples broken.

I turned off blurry reflection. Should I ever need that, I think I will cheat here and add the blurry effect in Photoshop. Did that once. I a lot work, but takes less time and ;-)

Thanks. Now I got that finally sorted out and my render process is running like a horse on red bull.

PhilW

I've done some tests recently with blurry reflections - to get the blurriness, it will be calculating multiple reflections and averaging the result - so for each pixel, it is producing multiple (don't know how many, and it will depend on your reflection quality settings) reflection rays.

For a flat plane like a floor, this sometimes isn't too bad - what really is a problem when applied to skin is that there are a number of areas where skin is facing skin (under the chin for example), so each of those reflected rays, now needs to calculate multiple reflections, and each of them... I think you can see that you quickly get exponential numbers of calculations. Even trying to limit the number of reflections to one doesn't help, as it always calculates a minimum of 2, even when set to 1 (I raised a bug request on this, just before the system disappeared...).

But good suggestions already about now to get around this.

Rhian-Skyblade

Yeah I figured as much regarding the blurry effects after I set the ray depth to 1.
Well, I am very happy with the highlight maps now. On dark skin they really work wonder. On pale skin that is another thing - but I will experiment that later :)

Dartanbeck

Glad you've got it sorted out!
I was going to mention that I was just experimenting around with Full Ambient Lighting. I read your first post, and I know you said 'No Amb Occ', but are you using Indirect? When I tried turning "Light through transparency" on in there, Wow... slug a lug!
I've really been getting some blazing renders lately - but all too often, I've been having to go with either Ambient Occlusion Only, or no Indirect Lighting at all - so I'm trying to find out what triggers that to take so long for some renders, and not for others - because I really like how the engine renders that stuff - just looks amazing.

With reflecting objects I've tried turning on Caustics as well - talk abut slow - but man, does it ever make a difference with shiny metals and jewels!

Rhian-Skyblade

My more recent Images do not use GI. Last time I did that took me almost five days to render. My poor computer wasn't taking that too well.
http://rhian-skyblade.deviantart.com/art/FanArt-of-Hive-53-183208740 (Star Gate Atlantis Humor FanArt)

It turned out too bright but after 5 days I was a bit too peeved to start over again.

So, next time I play with GI and ambience occlusion, it will be a night scene. Still have that on my mind... looking out of an old worn wooden window, a rose bush and a moon highlighting the darkened landscape... Maybe, if that is not going to eat my computer, I will try to add some clouds as ground fog.

But other than that, I stay away from it.

Caustics you say? Jewelry and gems? Sounds interesting. Never actually gave caustics much attention. I will see if I can add that in my next render :) question is how that will turn out also with skin and water ^^