Ground Plane Shadows Again!
mikethe3dguy
Posts: 515
I have to do a whole series of renders and absolutely need a shadow-catching ground plane for lights other than HDRI/Sun (mostly spots, but also emissives to some extent). I am dead in the water without it. The included ground plane does not work, and from previous experiments I recall that a primitive plane with matte enabled gives the same results. I have been here before, and trying to add shadows in post is a time-leach with unsatisfactory results.
Am I missing something - is there a fix to this? I can't believe this is only a problem for a few people, and don't understand how this problem has seemingly existed without a solution for years now.
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Comments
What included ground plane? In a default new scene, all there is is space.
Render Settings, Editor tab > "Draw Ground" on/off
Care to elaborate on why you say that doesnt work as a shadow catcher? (pretty sure it does)
If you want reflections etc, you can enable matte as you say, or you can get this: https://www.daz3d.com/iray-hdri-toolkit
I've tried it many many times, I just now rendered a scene with 3 G8 figures, a couple props, several spotlights and emissives. Ground plane is turned on and positioned properly. No shadows. Try it yourself: open a new scene and add just a primitive cylinder or cube and a spotlight. Add the Environment and Tonemapper options, then set mode to "Scene Only". Aim the spotlight at the primitive and make sure Draw Ground is on. Using either the Interactive NVIDIA viewport or an Iray render you won't see a shadow on the ground.
This is a known issue.
Settings, scene and render attached.
Playing with a primitive plane now with Iray matte properties added instead of the built-in ground plane. I do get a shadow but it's comparitively very faint compared to a normal solid surface. I've got luminance set way up already, much higher than I'd have in a typical scene. Don't think it's enough to be usable. Attached is an image of one scene with 3 different ground options. All three have the same cylinder, same spotlight with the same luminance settings. The only thing different is the ground surface under the cylinder in the 3 images.
These results are the same whether using distant lights, point lights, spotlights and emissives. It's only with an HDRI source that I've seen usable shadows on the DS ground plane or a matte-enabled primitive.
Thanks for providing the link, but it looks like this product just has a few useful shapes with the Advanced Properties -> Enable Iray Matte turned on. It's possible that the shapes by themselves have some value, but that Iray Matte feature is already included with DS. Unless you know different through personal use, my guess is they would behave identically to any object with that feature enabled - i.e. they'll only reveal very faint shdows with the light sources I'm having problems with. This is an HDRI toolkit, and my problems are not with HDRIs, but with all other light sources.
The occluders and reflectors do look useful though!
Daz Studio does not guess where you want the ground to be, and it would be very bad if it did. What if your floor wasn't at Y=0? The shadows would be all wrong. In screen shot, it shows lighting to be Scene only. Draw ground does not work with that setting at all. For shadows from scene lights, there needs to be a scene ground.
If you want to see the ground at all without a ground plane, you need to set lighting to Dome only or Dome and Scene and you can turn the dome off and ground on, and then you'll see a shadow from HDRI lighting on the ground plane at Y=0 in Auto Ground Position Mode, or wherever the Y position is in Manual., or Sun-Sky shadows if you pull the HDRI, but not shadows from scene lights. With Dome and Scene the objects in the scene will be illuminated by both environment and scene lights, but only the environment lights will cast shadows on an imaginary ground plane wherever it's established in the environment settings.
Thanks for your response. I think the "auto" position setting for the ground plane is DS guessing where the ground should be, isn't it? I did confirm that it was guessing right, and often when I use it, I set it to manual and adjust the Y as needed. My test scene has only a single object in the default 0,0,0 position so it's pretty easy for Daz to guess where ground should be in that case. If draw ground isn't meant to work with spot- and other non-dome lights, so be it. But a shadow catching solution IS needed for those lights. The Enable Matte option applied to a primitive plane as I mentioned produces extremely faint shadows, often not visible at all. You say that the ground plane won't show shadows from scene lights, almost as if that's the way it should work if I'm understanding you. I don't get that... why not? Don't you think it would be beneficial to have an invisible ground plane that caught shadows from all light sources? Otherwise there are no solutions for inside scenes with no, or minimal HDRI or Sun-Sky access.
Hmm, the "Scene only" environment mode seems broken. Same with "Dome and Scene" when Dome is switched to Off.
Even in a fully enclosed room, when toggling on/off the Dome, it changes the shadows. Shadows seem to only show up correctly when Dome is on.
It's almost as if downward directed light paths behaves differently if Draw Dome is off.
(Btw this scene is levitated well above the 0,0,0 position to like y=300.)
There's always pwCatch. For 3Delight, though.
It positions the ground only for environmental lighting. Sun-Sky rotatesa around 0,0,0 and HDRIs have an origin point. Scene lights imply a scene, with everything that entails. The ground is wherever it's put by the person setting up the scene. Most interior spaces have a floor and floors catch shadows no matter what the environment setting or light sources. And there is no ground plane unless you put one there, even if it's only Draw Ground from an HDRI. If there's no ground plane, Daz Studio doesn't know what to cast the shadow from scene lights onto. What if the character is an astronaut floating in space? Shadows would look out of place there.
If this is for compositing a still image, then you can render the subject once floating in space as a PNG with transparency or a beauty canvas with an alpha channel, and once with a white ground plane. Place the first in the image, and then use the second render as reference for painting in shadows. Since it's only used as reference, the reference image doesn't need to be converged beyond the point where you can tell where the shadows fall.
If it's an internal scene, they would need to do the 'shadow catching' render with a minimal scene set up (all walls on and all lighting active), otheriwse shadows are going to be all wrong when they composite the scene's figures back into the environment. There would be no bounce light off the walls, ,light through windows, etc.
I dont see why they need to use a ground plane and not their actual scene's ground. It's not going to add much VRAM to use their actual scene's actual ground over a plane primitive unless it's like some super high poly model with a 16k map or something.
Also, if they were to render shadows onto a white plane primitive as suggested, they could just add the shadows by layering this image as a multiply (or overlay) layer in Photoshop/Gimp rather than manually drawing shadows from a reference.
I'm wondering if the cause of the problem is not visible in the top left corner of the cylinder screenshot. The bit where it says 'DAZ Studio 4.15 Pro'. I have, in effect, done exactly that in 4.14 for the image below. I had the default ruins HDRI as the lighting (dome + scene and no lighting in scene), draw dome = off, draw floor = on, floor position - manual, floor Y = 0. And you can see the floor catches the shadow. I then dropped the five images with their transparent floor, but with shadows, onto a gradient background.
Regards,
Richard
I thought the OP didnt want to use an HDRI. They said they wanted to use scene only mode.
The problems i encounter are:
Try increasing "Ground Shadow Intensity" in Render Settings/Environment. It's close to the bottom of the list.
Well, the OP was asking for a plane, so walls etc are apparently not involved. To be honest, I'm not sure why the OP is asking about this at all. I've never had reason to go through all this stuff and don't render characters in a void.
i think they were doing an internal scene:
For internal scenes, you would have to turn on all walls and floor with all lighting active if you want to have a chance of having the composite parts matching together. You dont have to do this, but if you dont, then there is no bounce light and proper shadows. You also need stand ins for other objects that would impact the lighting if you're not going to have them in the render.
If you want invisible walls or w/e in the scene, then you have to Beauty Canvas out the parts you want, e.g., exclude the wall nodes.
edit: side note, do people actually use spotlights and other parametrics? I always only ever used mesh lights/emissives and HDRIs
I mostly light interiors with the light sources native to a scene, which are usually emissives, and spotlights with geometry. I'm not a fan of ghost lights, and rarely use them. I also often render lights or light groups to separate canvases and adjust in post.