Built-in sun and sky makes render grainy

Coryllon

Everytime I use the default sun and sky for natural light I get a grainy image when I render. If I don't and use another light source the problem is correctly but the shadows are crisp and nearly black. This hasn't been a problem in some renders with multpe light sources, but this scene is for an outdoor scene and I need accurate shadows that fade away on the edges. I am trying IBM Master to see if I can get crisp images and realistic shadows, but the tutorial on its product page is less than helpful. 

I suppose I'll start with some simple questions,:

1. Is HDRI a feature in DAZ studio or is it "These things in Daz Studio have HDRI properties." Beyond the standard "HDRI Stands for this" what IS it?
2. Can HDRI be achieved with props or does a scene have to have built in capabilities?
3. Is there a way to get (for lack of a better term) better resolution out of an image using Sun and Sky,
4. If there is no use Sun and Sky and not ruin the scene, how can I use other light sources and simulate the its positive effects and shadows?

For reference, please see the new user post for this May 2019 on page 2 "Just another day at the office"

Richard Haseltine

HDR is using an image with a lot of tonal information (hence the high dynamic range in the name) as a light source, the image is wrapped around the world (in some way - there are different mapping that can be used) and the colour value of the light in a given direction determines the light that is coming from that direction. It is possible, but not very efficient, to apply the HDR image to a prop as an emissive colour instead of using the built in  virtual dome.

However, Sun and Sky is not using HDR images - instead it is simulating the effect of Earth's Sun shining from a particular part of the sky - usually set by specifying time and location.

I am surprised that Sun and Sky would fail, as long as the Sun is actually up at the imte and place chosen and as long as the scene wasn't enclosed by an enironment prop (such as a modelled sky dome).

Coryllon

it does not fail. so much as it simply causes the image to be far less sharp than it would otherwise be. When I get home I will see if I can get sample, but it's hard to do given that removing the sun/sky and using teh headlamp changes the shadow position and trying to aim the distant light, when aimed correctly cuts off the very figures I am trying to aim the light at as they are in a wooded outdoor scene and the trees get in the way. Without the ability to soften the shadow edges with the reflection and spreading of the light, I do not know how to increase the render quality. and yes upping the render quality slider does has been tried; it doesn't help, just makes it take longer :) 

fastbike1

Don't use the headlamp.

Coryllon

well the headlamp is already set to only get used when there's no other light source

Fishtales

You don't need a distant light either if you are using Sun & Sky only. You might need one with an HDRI depending how good it is. Looking through the Distant Light to line it up also helps when using it.

Coryllon

I have the IBL Master, but that one is proving to be trouble using. the Default sun and sky lighting in DAZ studio yeilds that somewhat grainy image. All I've seen from threads to remediate that is use differentl lighting. I don't know if it's darker shading that's causing the issue or the lighting model itself. But I can't seem to take the grain out.

Richard Haseltine

You say it's a wooded scene - if that means it's got a lot of fairly dense models, including a lot of transparency mapped leaves (as opposed to leaves that are modelled leaf-shape) then that will slow things down, especially for "distant" lights (including sun/sky and HDR) as the light has to bounce around to reach the visible models, and calculating the passge through the leaves will add a lot of steps - the net result is that the render is stopping because it's hit the maximum time, not because it's sufficiently converged. If you have the 4.11.0.335 public Build you might want to try its denoiser.

SpottedKitty

Coryllon said:

well the headlamp is already set to only get used when there's no other light source

To DAZ|Studio, "other light source" is one of the three default lights we've had all along; Spot, Point and Distant. An Emissive surface or environment light (with or without HDRI) will not trigger the "headlamp off".

Coryllon

this is hitting a 5000 iteration limit, not a time limit. and yes, this is just using lighting, not emissive surfaces. 

Hopefully this helps. I also have it set to 99% convergence

JamesJAB

It looks to me like you have the "Sun-Sky Only" set at the default time of day.  This reduces the amount of light coming off of your "Sun", gives everything long shadows, and warms up the color giving everything more of a red shade.

You might want to try setting the "SS Time" to 17:00:00 or 16:00:00 and see if that renders better.
Also while rendering you can open the side bar on ther left side of the render for some on-the-fly adjustments.   Here are some usefull ones to play with in the tone mapping section.

Shutter Speed : lower values brighten the render, while higher values darken it
Burn Highlights : setting this makes the light areas brighter
Crush Blacks : setting this makes the dark areas darker

Keep in mind also, the 5000 itteration limit is something you can change.  You can set any value from 1-15000 (Or more if you edit the slider options)

You might also want to try rotating your light using "Dome Rotation" to somewhere around 180 to get your Heroine out of the tree trunk shadow.

Padone

Also with the sun-sky model you can use a null to set the position of the sun and you can adjust both the sun size and power to get the light softer. It's a very simple and versatile light system in my opinion.

Szark

Padone said:

Also with the sun-sky model you can use a null to set the position of the sun and you can adjust both the sun size and power to get the light softer. It's a very simple and versatile light system in my opinion.

Or use the built in Sun Dial which allows a visual reference to the sun's direction. 

Coryllon

Thank you for all the suggestions, I had set the time up a couple hours, I moved it up a bit more. so that helped a bit. 5000 iterations should be more than enough for most cases, this still takes 6 hours to render, give or take I rarely see improvement passed 5000. If I change the resolution then "shrink it" with GIMP, will that increase the DPI at all? I KNOW you can can do low light renders and get better results, so why can't I? what hurdle am I not jumping over? 

Also I wanted to give the impression she's fighting in a wooded area, so I can't change the light direction because there are no trees over there to reduce load time, file size and render time.

Padone

Coryllon said:

5000 iterations should be more than enough for most cases, this still takes 6 hours to render

I'd strongly suggest you to keep the iterations around 500 and get a denoiser. Unless you're looking for sharp details that is, that unfortunately the denoiser will not be able to retain.

 

Coryllon

try as I might, 5000 seems to be the limit I need. I was able to, with a few tips in the contest forums, get SOME of the graininess out. and take out enough blurred edges to make the wood in the axe look more weathered and rough without ruining the straight sharp edges of the grass and rapiers. It does seem I am at the limit of SOMETHING. I'm use base genisis 8 and the active view port. does that change how sharp I can make an image or is that set by the convergence?