Iray shading issue (solved)

logicalOctopus

I recently rendered these images. Both of the same identical scene (including lights) and I seem to be not getting the correct lighting with Iray.

The one on the left (done with 3Delight) seems to be more like I would expect from the placement of my lights. Notice the lighting on the face in particular. The main light comes from the left and the right side of her face (to us) is shaded. Not so on the Iray image. The Iray image does have floor shadows though, and you can see from those that I also have a secondary light coming from our right.

What can I do to better represent the lights as I set them up?

I notice that shadow settings on the light are not available when I have the Iray renderer selected. Also I wonder if there is any difference between setting a light that is 50% gray at 100% intensity, or 100% white at 50% intensity. Those two lights should behave the same in my opinion, but maybe not? In any case it seems my secondary light (the one from the right) is not depicted accurately with Iray. Its a shame because I really like the output from the Iray renderer otherwise, even though it takes an eon to produce. In fact, the secondary light in this scene is set with an orange cast at about a 75% color value and about a 75% intensity as well.

Is there anything else I should know about Iray that I need to set? How can I control light intensity properly, and how can I have control over shadow intensity and softness?

Thanks for any insights.

 

 

Oso3D

You shouldn't be using Intensity in Iray, but Luminous Flux (or similar, depending on the light type).

So if you want one light to be half the intensity of the other, make one half the Luminous Flux of the other. Roughly speaking.

 

logicalOctopus

Well, there must be something else going on, because while trying your suggestion without luck I tried deleting both lights and I still get a similar render in Iray, so there must be another light source from somewhere. My headlamp on the camera is (and always was) turned off! Where might the other source be? Is there an ambient light source somewhere?

fastbike1

Iray is a physically based renderer. It will simulate real lighting.

You control shadow intensity in Iray the same as you would control shadow intensity in a photo studio. Bigger and closer light = softer shadows. Smaller and farther light = sharper more intense shadows. The Iray lights can have geometry, effectively becoming softboxes. If you have an Iray light on the right, it explains why you don't have shadow on the face. You can see your light placement by looking at the shadows on the floor. You have one light on the left and in front of the subject and another light on the right and generally parallel to the subject. Iray also has a default HDRI light (dome) which will lend some additional overall lighting to the scene if you have slected "Dome and Scene", in your Environment setting in the Render settings tab./ Dome and Scene is the default setting.

You control intensity by changing the setting for luminous flux (lumens) in the Parameters>Light tab. You can olny change the color of a photometric light by changing the coor temperature. If you want the effect of a gel, you either need to shine a photometric light through a colored translucent primitive (i.e. a gel) or use a mesh light (slower to render) with the color in the emmision color setting.

As far a render time, do you have an Nvidia graphics card (GTX or Quadro)? if so make sure it is checked in the Render Settings>Iray>Advanced dropdown.

Also, unlike 3DL, Iray renders faster with more light.

Connatic

What is your Environment Mode set to?  Perhaps an Environment Map is cast light.

mjc1016

If you did not disable the default Dome, then yes, there is an Environmental light being used.  The default setup has the dome enabled and an HDRI plugged in.  Switch to Scene Only in the render settings.

Tobor

Choose Scene Only for the environment, and render one light at a time. You can determine direction and intensity of light in this manner. If you were shooting stills or video, you'd do the same thing (well, you'd also use an incident light meter, but Iray stinks in this regard.)

As noted above, leave Intensity at 100%. Adjust the lights based on the luminosity value. 

logicalOctopus

Yes, thanks for all the answers. I had a dome with an environment map which over powered my lights. When I turned the dome off the lights hardly lit the scene at all.  So I tweaked my lights and turned up the luminosity values. It turns out I do like the dome on, but with modified settings.

I gleaned a lot of info off these videos, too:

 

Really should switch all my surfaces to use Iray shaders as well. Wow, there sure is a lot to learn about Iray.