Volumetric Materials and Backdrops
algovincian
Posts: 2,636
Can anybody confirm that when the camera is looking through a volumetric material (like a cube setup for SSS haze/fog), the backdrop is ignored? I am currently using the 4.9.3.56 Beta, and am trying to figure out if it is a bug, a limitation in DS's implementation of Iray, a limitation of Iray in general, or a problem with my install. Thanks in advance for any info if anybody has any experience with this.
On another note, I believe there may be other things corrupted with my beta install (which is why I mention this as a possibility). For example, if I create a sphere, move it from 0,0,0 to 0,100,0, then create a null at 0,0,0 and parent the sphere to it, the sphere ends up moving from 0,100,0 to 0,0,0. This does not happen in the release build I have installed. I seem to recall reading about others complaining about this behavior.
- Greg
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Just uninstalled the beta I was running, re-booted, and then installed the latest beta 4.9.3.71, and both issues remain the same.
- Greg
I was simply dragging and dropping from the scene pane, so there were no options. I did try right clicking on the sphere and change parent, which did pop up the dialog. Parent in place was indeed unchecked. After checking it and changing the parent, it must have set the default behavior. When I drag and drop from the scene pane now, it works! Thank you, Barbult!
I don't believe I ever changed that setting, but who knows. I'm just glad it's all sorted now - thanks again.
/HT
- Greg
If by 'ignored' you mean it renders the volume black, yes. At least in my limited experience with basic volume tests 2 weeks ago on 4.9.2.7.
I assume it's by design. I then added background image for my volume test scenes. Others pls confirm.
Sorry - I should have been more clear. The following render is the WIP scene (before starting to play with some ground fog):
The scene is lit by an HDRI and a little bit of emission from the visor. The BG is just the HDRI, only at -5EV compared to the rest of the scene (accomplished by rendering the view of the HDRI alone through the camera, adjusting the exposure -5EV, and setting it as a backdrop).
In this next quickie, undercooked render of the scene, I've added a simple ground fog cube onto the right half of the terrain. I've also changed the backdrop to be a checkerboard pattern so that it's easy to see that the backdrop is being completely ignored for the areas where the camera is looking through the volume:
Hope this explanation makes some sense.
- Greg
I'll echo Mythmaker's post: I've rendered volumetric raindrops using the built-in HDRI and they've all rendered black. I've seen the same thing when initially testing volumetric materials too -- volume turns black with the default HDRI. I had DAZ not render the HDRI dome though, which is obviously different than your tests.
The interesting part is that they take on color when an actual skydome object is used, such as Iray Worlds Skydome.
@ mtl1
I went back for a quick test, then I recall my temporal conclusion: the volume renders black (more precisely the volume doesn't even render) against Background in Interactive mode.
When switched to Photoreal it renders "correctly". But it just ignores the Background image.
So, @ algovincian, I can confirm your findings...
Haha, IIRC from last night's test renders, mine doesn't even show the white parts... o_o
Thanks for taking the time, Mythmaker and mtl1 - I really do appreciate the confirmation. I've got a couple ideas for other ways to accomplish this (that may well render faster and cleaner anyway). One of them involves adding some more nodes to every existing material in the scene, and the other trying to squeeze a volume pass out using canvases and LPEs.
My initial investigation has come up empty on volume LPEs. I'll keep looking into it.
- Greg
Okay, this is weird. It's not ignoring the background HDRI for me anymore, and I can't figure out why. Weird.
Anyhow, it now recognizes the HDRI image behind it. I created a new primitive, converted it to Iray Uber, and proceeded to turn everything off -- including glossy inputs -- so I can get all the refraction settings out. Now it renders properly, including the HDRI background.
PS. Please ignore the toolbar. That's from Room Creator 2 :)
Looking at the screenshot you have Refraction Index at 1.5 which is a solid object like rock. 1.0 is a vacuum or air, 1.33 is water, 1.35 is sea water the higher you go the more solid the sphere will get. Raising the Transmitted Measurement Distance makes it less murky; Raising the Scattering Measurement Distance makes it clearer; raising the SSS Amount makes it like milk; Transmitted Colour determines the colour of the volume. The SSS Direction determines how the light reacts to it in relation to the camera angle.
Set the Sphere to 1.33 and 1.0
Volume: Thin Walled On
TMD: 2.00
TC: 0.32/0.96/0.15
SMD: 0.10
SSS Amount: 0.0050
SSS Direction: 0.00
That should be Green Water,I hope, then Play about with the sliders one by one and view the results each time.
A non-fancy typical iRay volume renders HDRI dome image as expected (in Photoreal of course).
To make Volume acknowledge HDRI dome image, it is not enough to turn Environment tab > Background image to None.
The Environment tab > Drop down menu on top > Backdrop need to be changed to None.
Background. Backdrop. Enviroment...Dome... Don't you love all this wording... (that's why I would avoid labeling Daz HDRI image as background post-iRay era lol)
Attached G3F + ethereal aura, iRay HDRI image, simple volume.