Iray - Can you create an Ambient Light Source?
LeggyBlond
Posts: 124
I've been trying to work out how an Ambient Light can be created in an Iray Render much like the 'Advanced Ambient Light'. I know a Skydome could be used but that assumes that you don't need the skydome as a background as turning it into a light source will burn it out.
Anyone have any ideas?
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What are you wanting to achieve? Usually in Iray "ambient light" would come from an HDR iameg loaded in the environment or from the dome made into an emitter (which shouldn't, with the correct settings, burn out though it will be slow). For a broad source you could use a light with its geometry set to soemthing other than point or an object with an emissive sahder applied.
Reading between the lines of your post, perhaps this new thread will answer your question:
http://www.daz3d.com/forums/discussion/61704/using-iray-with-3delight-skydomes-how-to
It uses the Iray Environment for the ambient light source, plus allows a traditional skydome for a backdrop. Enough light from from the Iray Environment dome lights both the scene and the interior of the skydome. This approach is generally more efficient than making a skydome geometry emissive. That's a very large area, with a lot of facets for Iray to calculate as individual light segments.
First of all:- the effect I'm trying to dreate is that non- directional ambient light you get with Age of Armour's Advanced Ambient or UberEnvironment2. These lights give that sort of real world subtle shadows which are non directional and can be used in conjunction with main directional lights.
I have tried on various occassions using the skydome as an emitter but it seems to entirely depend on the background image as to whether you get burn out. I well saturated image iis not so bad but one with say a light blue sky and clouds quickly starts to was out with intensity. I got away with a reasonable level of intensity with 'Max II - The Road Warrior' http://www.daz3d.com/gallery/#images/71290/ But the sky was originaly much more intense
I will be experimenting with Light geometry variants as Richard has suggested as that may be helpful
In the midst of writing this I have tried the 'Section Plane Node' as explained in Tabor's tutorial which does at least go a long way to answering my question but there must be some way of creating an Ambient type light like those mentioned above. (very helpful - thank you)
A question I must ask...where do you guy's get all this information? I have searched high and low for detailed explanations about the Iray settings and what they actually do and all I can find are simplistic blurbs on various settiings in the so called Manual
heh, for me some of it comes from experimentation or from geenralisation from other applications or systems, other parts from things that have been said by the developers or QA people in official threads or the occasional reply to a post.
Thank you Richard, that's much the same way I have had to learn.
This is no criticism of DS but Software authors in general:- Most Software developers/writers seem to assume that because they understand a particular function they feel no need to enlighten the user as to it's function. Some things are to a greater or lesser degree are almost self explanatory but most things are almost cryptic. The 'Tone Mapping' panel as an example I understand extremely well as I am a photographer, Light temperature in degrees kelvin is very easy to understand but things like 'Rendering Converged Ratio' , the Optimisation panel which I now have a little clue about but unless one has got gob loads of GPU Ram one can be trying things out forever....I mean - 'Max Path Length' default '-1' Uh!.
I'm currently running what is considered a pretty fast machine MSI Mb 4Ghz AMD 8 Core 4.3 Max, 32Gb 1600 Ram), and I changed my GPU with an identical version except it has 4Gb instead of 2Gb and hopefully when my new upgraded PSU arrives I will be adding the original 2Gb GPU in the second slot (or swapping slots)...but that's still only 6Gb compared with many of the artists that seem to have 4 PCIe x16 slots with massive GPU capacities.
Digressing slightly, when I changed my GPU from 2Gb to 4Gb I didn't expect any big speed/time changed but in fact in the case of some renders the time was reduced to around 1/6th which makes little sense.
No, that's only 4 GB...
Video memory doesn't stack. In order for a card to be used, the scene must fit in that card's memory. So, if the scene is 2.1 GB the 2 GB card won't be used, but the 4 GB one will. What would be better is to dedicate the 2 GB card to run the display needs of your operating system/monitor(s) and leave the 4 GB card for just rendering (won't be hooked up to a monitor).
Also there isn't a linear relationship between the memory size and speed...a doubling of memory won't cut the time in half, that is governed more by the number of CUDA cores available. More memory will help speed a little. But if the scene is close to about 1.5 GB in size (in video memory terms) the 2 GB card may have been discarded, because 1/4 to over 1/2 a GB of memory is used by the OS/display purposes, so the scene was actually being dropped to CPU only, instead of actually using GPU acceleration...it wasn't actually able to fit in the AVAILABLE video memory (that's the key thing to remember...the render gets what's left of the video memory).
Max Path Length of -1 just means don't use this setting. If you set it to a positive number it will act like the Ray Trace Bounces setting in 3Delight, I believe, limiting how far the renderer will follow a ray before calling it quits with the current colour (so it's a speed/quality setting). You can use 0 or -1 in the same way for Max Time and Max Samples to remove those from consideration as stop conditions, so the render will keep going until it's as converged as you want.
Thank you for the Tech information, that was helpful.
In light of that it then doesn't make sense that my initial temporary card swap was an MSI Geforce GTX 960 2GB 1024 CUDA Cores, to a MSI Geforce GTX 960 4GB 1024 CUDA Cores which rendered what was a 6 hour render in just over 1 hour. Although I'll swap slots later I now have the 4Gb Card in Slot 1 and the 2GB card in slot 2 - ok probably the wrong way around but last night what was a render of around 1 1/2 hors took less than 15 Minutes....non of that makes logical sense.
Also whilst watching a Tutorial by 'Sickleyield' there was 4 GPU's so if adding GPU's makes little difference why have 4 instead of 2 - one of the display and big Ram card for rendering
Thanks Richard
Like you said, experimenting seems to be the route to take with Iray
What could have happened when you switched form a 2Gb card to a 4Gb card was that the scene was too large to be rendered on the 2Gb card. If there was no other GPU selected (or installed), Studio would switich to CPU rendering alone.. That would be slowest. With a 4Gb card, the scene can fit within card memory and would take advantage of the Cuda cores. If you have two cards it would make sense to run the monitor on the smaller card and let the full 4Gb be available for rendering. Even better would be running the monitor off of onbard video if you have it. Smaller scenes would be very fast.
I don't think the location of the cards matter, but I only have a single card so can't experiment.
4 cards, with the same amount of RAM...or a scene that would fit on all 4 cards (say 3 are 4 GB cards and 1 is 2 GB) would get the advantage of using all the cores of all the cards. So it would be faster. A scene that won't fit on the 2 GB card would just use the 3 4 GB cards and would be slower.
Memory is the determining factor in whether or not the card would be used...but after that, has little impact. And more memory means a larger scene can fit. Having a card handle all the display OS tasks frees up the most amount of memory on the card used for rendering.
Fastbike...on some motherboards the card in slot 1 will ALWAYS be the display card.
Whatever the technical verities are, the fact is that on my machine at least, a test scene I did yesterday three times with various combinations of cards on or off, having both cards on did seem to refute what is supposed to be. Using both GPU's the test render was quicker by a country mile than turning off the monitor card or any other combination - The 4Gb GPU only (Monitor GPU off) took 19 Min 23 Secs with both cards on it was 11 Min 11 Secs!! - getting on for twice as fast. The scene by the way is 1920 x 1080 Pxls, 5.6 Mb Daz file size (how that transcribes to video ram I don't know). Render Qaulity 1, Max Time to Max, Max Samples to 15000, Rendering Converged Ratio 99%.
My point being that if the software chooses a specific card because of file size then fine but why turn off the monitor GPU when clearly it can often speed things up? I can still carry on with other stuff albeit a bit slower on my machine and besides, when I do a big render I usually get on with other non PC related stuff or use my Laptop, Tablet etc.
Of course I could always break the bank and buy a card that costs as much as a small family car...but where does it end?
Anyway, I'm still working on my original question regarding the various ways of creating an Ambient lighting effect in Iray whilst using a Skydome..
You could try using Finite Dome in Iray. Reduce the size of the dome until it fits inside the Skydome and turn off Draw Dome, this only affects the Iray dome so it doesn't draw the HDRI as a background, this should give you the HDRI light inside the dome. I have done this with buildings but not with a Skydome.......yet
Fortunately, Daz (mostly) uses the same wording for features as found in other applications that use Iray, such as 3DS Max and Maya. These have slightly better documentation. In this particular case, and according to how these programs document it, -1 means "infinite." Well, not infinite in the true physical sense, but there's no artificial barrier to when Iray decides it has bounced the light enough. Depending on the scene, it could be dozens or even hundreds of bounces; each bounce chews up render time. In most scenes, -1 is perfectly fine. But in scenes with a lot of reflections, expect sitting around twiddling your thumbs.
As I also do programming, the programmer's manual for Iray, as scant as it is, also helps in trying to understand what is not feature documented. I try to pick up as many nuggets as I can in these arcane places.
For the sectional plane trick with domes, it was Richard who brought it up in a thread about removing the ceiling in closed interior sets, so that overhead lights could shine in. We were talking about such roundabout things like removing polygons with the Geometry Editor in D|S, or doing an export to Hexagon to chip off the top. I had completely forgotten about the sectional plane. So we share tidbits like this in the normal course of thread discussion in the hopes that a rising tide floats all boats.
As for your question of producing ambient light: this is the purpose of the Environment dome in Iray. It's as globally ambient, or as highly directional, as you want. You don't actually need lights to produce the ambience. It simply comes from the environment, just as it does in the real world.
Thank you Fishtales
It goes to show how many more things I have yet to learn about Iray and it's possibilities. As you have used this method could you tell me the way the Finite Dome scale is reduced, With average size skydome in place I've tried bringing the Dome Radius and Dome Scale Multiplier down to 10% but as yet all is still black and there is no way to actually see the Finite dome scale in relation to the skydome
Hi Tabor
I was trying to create an Ambient light within a skydome which the base Iray light does not penetrate. 'Fishtales' steered me in the direction of using the 'Finite Dome' setting but as yet I have not been able to make that light up anything within an Enclosed skydome. The base Iray light is directional (Dome Rotation) so surely that's cannot really be considered as an ambient light. The closest I have come is with a particular skydome texture which was high in both colour saturation and contrast which meant that I could turn it into a low level emitter without significant burn out. HDRI backgrounds are not generaly suitable as detailed backdrops unless they're like some of the proprietry versions like the HDR Iray Interiors/Exteriors and the problem with those is that camera direction and placement are all important which is very limiting.
I live in the hope that some bright spark will work out and make an Iray version of something like 'Age of Armour's' Advanced Ambient Light.
The Iray Environment with a plain gray image produces a nicely bland, non-directional ambient light. I have a couple of TIFs I created in Photoshop at different gray levels, and load those in when I want absolutely no shadows. You can also control lighting intensity with the Environment Intensity control. It is the real-world photographic analogue of the light tent.
Of course, if you want a tinge of color, you can add that in your plain Environment image.
How you then introduce a skydome image (note: these aren't the same thing as the Iray Environment dome) is a subject of some other threads. The plane sectioning tutorial I posted is one way. Another is to use a dome you've manually modified with the Gemoetry Editor in D|S to remove polygons on the front and/or top. Both approaches may parts of the mesh invisible, and therefore, will no longer block the Environment light. There's also flat and rounded cycloramas, large cove backdrops, and other techniques. Each one has its uses, but all will let the light from the Iray Environment into the scene, and provide lighting for the backdrop/dome.
Drop the idea of using an additional skydome. It's not needed. You can't make it work in an enclosed 'physical' skydome...you can, however, 'chop' up that dome to let the light in...so it's now more like a sky bucket or donut...
There is a full environment included...it consists of a 'nonphysical' dome and 'floor'. You can use that dome for lighting, backdrop or both, depending on the HDR image you plug into it (a very large, resolution HDR can be used for both lighting/backrop). There is also a Sun/Sky mode that uses physically accurate modeling to simulate sunlight/time of day.
As to rotation...yes it is ambient, even rotated. Think of it as just providing the main compass direction. And orienting the dome to the angle you want to match up with the HDRI is why it is there in the first place.
In my sig there's a list of HDRI sites...there are quite a few of sufficient resolution AND range to do double duty for both lighting and backdrop. You can also drop a jpg (or other format) image into the 'backdrop' that will be independent of what the dome uses for lighting.
Gradient images work nicely, too...dark grey bottom/lighter grey top.
I think maybe I have not made my question clear. The reason I want to use a Skydome (like LDP and such) is simply because I want a proper background for such scenes as terrain based. HDRI backgrounds generally are more about light than their background image clarity. Of course I know I can create a mask and add a background later but that often does not look as good as having one present in the first place. Some of the alternatives you mention are fine but by having an ambient light there to start with not only creates a more natural base light but also allows one to limit the main lighting to suit to avoid casting shadows onto the Skydome.
Using some of the weird and wonderful methods you and others suggest defeats everything I am trying to achieve. If I'm creating a landscape, I want a back ground that suites the environment and in most case a Skydome fits the bill better than most anything else because it allows both dome rotation to suite and a multitude of possible camera angles. I do know of course I could use an Iray Section Plane Node but I am trying to do without that when I can.
To best illustrate this the link below shows a scene I quickly created which allowed me to use the accompanying skydome (which suites the scene of course) in a light source - just enough before colour burn out. If I had used some of the base suggestions related to using the base Iray lighting (turning the scen dome off) the net result would have in a nutshell......looked ^%$p.
http://www.daz3d.com/gallery/#images/84566/
I also got away with upping the Skydome Emission in this image the subtle shodows around the ddiagonal supports as an ecample:-
http://www.daz3d.com/gallery/#images/71290
I think maybe I have not made my question clear. The reason I want to use a Skydome (like LDP and such) is simply because I want a proper background for such scenes as terrain based. HDRI backgrounds generaly are more about light than image clarity. Of course I know I can create a mask and add a background later but that often does not look as good as having one present in the first place. Some of the alternatives you mention are fine but by having an ambient light there to start with not only creates a more natural base light but also allows one to limit the main lighting to suit to avoid casting shadows onto the Skydome.
Using some of the weird and wonderful methods you and others suggest defeats everything I am trying to achieve. If I'm creating a landscape, I want a back ground that suites the envviroment and in most case a Skydome fits the bill better than most anything else because it allows both dome rotaion to suite and a multitude of possibel camera angles.
To best illustrate this the link below shows an scene I quickly created which allowed me to use the accompanying skydome (which suites the scene of course) as a light source - just enough before colour burn out. If I had used some of the base suggestions related to using the base Iray lighting (turning the scen dome off) the net result would have in a nutshell......looked ^%$p.
http://www.daz3d.com/gallery/#images/84566/
Are you using linear workflow?