Iray - how does the ground option work?
XoechZ
Posts: 1,102
Hello!
I use DAZ Studio 4.9 and render in Iray. I have set up a figure kneeling on the floor. But I did not create any floor, just the figure and 3 mesh lights. Now, in the Iray render settings under Environment I set the Environment Mode to "Scene Only" and Draw Ground to "On".
Now, as far as my understanding goes, when I render the image, I should get some kind of ground with visible shadows from the figure. Like a shadow catcher plane. But there is nothing. There is only the figure. No ground, no shadows. Nothing.
Is this function broken, or am I doing something wrong? How is the ground function used correctly in Iray?
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Comments
Are you sure the figure is actually on the ground. It may be that it is floating above the ground plane and not on it. Try Ctrl-D with the figure selected and it should drop to the ground. If it disappears then either lower the camera or move the figure back until it is visible and then either scale it to fit or move the camera closer.
I have only got the Iray Ground to work with the Iray Dome HDR lighting or the Iray Sun.
It seems to ignore the DS Photometric lights.
I don't know if that's a bug or just not enabled or just me!
Mesh lights produce only diffuse lighting, so any shadow detail is likely to be faint.
And as noted above, be sure the figure has been "dropped" to the ground level - Ctrl-D or Edit->Figure->Move to Floor.
Hi Tobor
Are you saying that the Iray Ground actually can catch shadows from a DS Spotlight?
Ok, here is a test render to show the problem. The figure is on the ground of course.
In the left image I used 3 mesh lights and Ground on. No ground and no shadows as you can see.
In the center image I have attached an actual plane to make the shadows visible. As you can see, shadows are enough to see.
In the right image I deleted the mesh lights and used the sun and Ground on. Now the ground is there (shadows).
So it seems that the ground function only works with the sun. Too bad, because I never use the sun. I like indoor and studio lightning setups. I hope this will be fixed soon!
The DS spot is an actual Iray spot when Iray is used...so yes, it should be able to.
I have just tried it and the result is the same as with mesh lights. It does NOT work! No ground shadows with spot lights.
The sun/dome seems to be the only light source that works with the ground. Too bad.
Post a screen capture of the Environment tab settings in the Render panel.
I don't have 4.9 (waiting for the first update), but shadows definitely work for all light types in 4.8. I'd be surprised that this is a 4.9 bug that wasn't caught in beta testing.
You're right...just tried almost every combination I can think of and by itself with just the ground, there are no shadows.
Dome and dome/scene also give shadows, but they don't if you don't have something set in the environment settings. I didn't try a 'neutral' HDRi on the dome to see if it shows the light's shadows or if it is just the HDRI's shadows.
I could have sworn I did a bunch of renders a while ago with just a spot...but I may have had a plane primitive in the scene, I'm not sure (I didn't bother to save any of those runs as scene files, so I don't know anylonger).
Here is the screenshot.
Of course shadows are working for all kinds of light, especially in Iray where you cannot turn off shadows (like in 3Delight).
But I am talking about the Iray Environment Ground. This seems to work with the sun only. No other light source casts ground shadows on that "Environment Ground". Simply look at my images 3 posts above.
I'd compare it to 4.8 to see if it's a change in functionality. but oh well.
XoechZ is right. DS spotlight does not cast shadows on the ground plane.
So is this a bug or a feature?
I would really like to use the ground shadows. It would be nice for composing and postworking to have a figure casting shadows on the ground, but having a single neutral background color.
I just ran a couple more...and with dome/scene, it's just the HDRI shadows from the dome.
So without an actual geometric ground, there aren't any shadows.
And these runs were in 4.8, 64 bit (double checked and that is what is still on that machine).
Just tried this in C4D and Iray Ground is the same, only Sun or Dome shadows work.
Must be a feature then...
Ok, thank you all for you help and testing!
Well, I guess I never tried this combination before.. Looks like 4.8 behaves the same way, so it's not a new bug, but it's also not a consistent feature (why have the ground shadow controls in Scene Only if scene lights won't product a shadow on the virtual ground?).
So what we've discovered: the shadow catch feature of the virtual ground works with the sun in sun/sky, or the applied lighting in an HDRi in dome only or scene + dome. There are plenty of (free and paid) HDRi's that provide various light styles that will not only produce the lighting you want, but ought to give your the shadows as well (assuming the light sources in the image are fairly distinct). See mjc's sig line for HDRi sources.