Distant Lights: seen what I newer get: Viewport vs render results

wolfprivat

I' m still a newbie, and for sure i did something really wrong, but now i am back to the wall in trying to use a distant light in a scene where the viewport preview and the final render show

the same light direction.

From the early beginning with my Daz 4.9 installation i wondered why i always have such a bright backlight or light from any direction in any scene, regardless of what light direction i define.

I setup a test scene to show what i mean.

In the test scene all headlamps (camera, render settings) are deactivated.

There is only one distant (sun) light defined that should illuminate the front of my  model.
The viewport display showes exactly what i expect, the light comes from the front ONLY.

However on the rendered image the light sometimes comes from the back, sometimes from the right, unforseeable where it comes

from. In extrem cases there is about 180 degree divergence in the light direction of what i defined.

I tried this on several scenes, there always is a big divergence in the light direction between the viewport and the rendered

image. This only happens on distant lights. When i define indoor scenes with some (linear) point lights to brighten parts of

the scene, everything works as defined, light directions in the rendered image are the same as shown in the viewport.

I do not have much time now, but i added a sample image with, as i mean, a very strange render result is shown.
 
In this case I only defined ONE distant light, nothing else: one distant light directly to the front of the model (as seen in the viewport),
i defined it with a warm colour temperature like on a late afternoon.

All headlamps switched off. Yes ALL!

Resulting rendered image: the models skin is in the shadow (why?), but the shadows the model throws behind her are correct.
How can a model throw a shadow, when there is no direct light on her skin?
(the models skin is pale-purple, not warmed up by the yellow/red defined sunlight)

Is this a bug or a feature?

And more on there is a strong light from the right side, what i did NOT define.

In other scenes the light sometimes comes from the back, or from the left, i cannot forsee what will be in the render.

Could it be a good idea to reset my Daz Studio installation to its inital defaults?
Would this harm all my purchased content? (or already defined scenes?)

Has someone any suggestions what is going on or what did i wrong?

System: Intel I7, Win 7 64 bit, Nvidia gtx 960 4g, current driver, Daz 4.9.2.70 pro, iray render

MelanieL

First a question: what lighting setup are you using in the Environment tab of the Render Settings panel? If you only want to use your distant light then you should set it to "Scene Only" otherwise it will be picking up lights from the default HDRI or from the sun/sky.

Tobor

In addition to setting Scene Only to avoid any contribution from the environment dome, two things:

1. The regular viewport is a poor estimator of light quality. If you want to see how things will look when rendered, switch from the shaded view to nVidia view. This will display a real-time Iray image in the viewport. Your 970 should be able to accommodate this view reasonably well, though with some lag, especially if you choose the Aux Viewport and dial down the output to a reasonable size.

2. You can always check the direction of lighting from distant and spotlights by selecting the light in the View list. This is not a camera, and you cannot render from it, but you can use it to set the direction of these lights.

 

wolfprivat

Sorry for coming back so late, i was'nt at home for a while.

Thank you MelanieL, in fact i overlooked this parameter in the render tab.

Setting the light to 'scene only' brougt the viewport preview very close to the render result. Later i switched back to 'Dome and Scene' but then i set the 'Environment Intensity' to less than 10%, shadow intensity to 5%  and pushed up my distant light to 45,000 lumen

what is close to sunlight in the late afternoon. The default value of 1,500 lumen is less light as a theater spotlight and was the reason for the enormous impact of the environment lights.

Sigh, i know all these things from years of experience in photography and video cutting, but i have to learn where all the knobs and sliders in Daz Studio are.... and i am willing to do that!

Thank you also Tobor!

I agree with you, that the viewport is not perfect for the pre-render check, but it is not that bad.

For the last fine tuning prior to a (long lasting) render i use the quick render function. Setting the viewport to real time iray is not such a good idea. Well, yes, my gtx 960 is quite powerfull, but when it shall render in realtime, it gets 'steamy', the fans running as mad and there is a big lag in display. This is not useful for fluent work.

> 2. You can always check the direction of lighting from distant and spotlights by selecting the light in the View list <

That was exactly what i did as you can see on the left side of my posted picture (titled: how the light is defined...). My fault was: too less luminous flux, to much environment light.

Well, agin thank you both for your fast reaction, it make me feel good, when i'm stuck in quicksand...

Next themes i will concentrate on are: unwanted lights (thread   http://www.daz3d.com/forums/discussion/111366/vendors-please-stop-including-mesh-lights)

and too much mirror-like reflections in any scene, where they should not be:

samples: i bought the scene 'Asia River'. I like it, it is a nice tropical environment. But why do the wooden boat parts (above the water line!) are reflecting the entire sky like a mirror?
I also got 'Outdoor shooting range'. It's also nice and useful. But if you have a closer look to the grassy ground, you'll find out that it mirrors the light as if it is covered with water or ice.

And why are so much female and male figures skins glossy as if they are prepared for oil wrestling. Err, good idea, i'll should create such a scene next...

and last not least: there is the 'So Wet Bundle' on sale now.
Oops, i thought it is already part of all surface material sets like wood, meadows, ground, cloth...

:-)

 

fastbike1

Just a note of caution: Don't expect to use real world lumen values in Studio for the photometric lights