What Am I Doing Wrong?
PhoenixDeFalco
Posts: 71
Hello, my name is Phoenix. I need some advice. I have recently started trying to use the new NVIDIA Iray Render Engine for DS 4.8. However, for whatever reason, no matter what I do, I always end up with either a black image with a tiny light source, with no illumination to the scene, or I end up with a crap render that doesn't incorporate lighting at all, and looks just like the Viewport with Preview Lights disabled. Could someone tell me what I am doing wrong, and how I could fix this issue? Please find attached a text file listing the settings I'm using. Thank you so much!
~* Phoenix DeFalco *~
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Hi, I'm not an expert, just someone also learning how to use Iray. I can't tell by the text if you have the default HDRI set in your environment tab, but if it is and you want the lighting from it, I think you might want to set it to Dome and Scene. If not, my best guess is that you don't have to lighting strong enough. It would help if you also showed us the information from each of your lights and their settings. From my experience, limited though it is, usually I get a black screen when the lighting is too low. If your lighting is from a particular Iray product, let us know that, too. Someone with the product might be able to help you with settings. It would, probably, help to add a picture of your render, too.
If you are using scene lights only you probably need to adjust the Tone mapping settings - lower shutter speed or f-stop, higher Film ISO. How are you lighting the scene?
I have a point light and a linear point light. The point light is set to 100% intensity, with a 1 intensity scale, and 1.5 decay. I dont know what this means, though: "lower shutter speed or f-stop, higher Film ISO." What do these properties mean? Also, is there somewhere I can get a full dictionary for all these parameters? these settings are so much more detailed than 3Delight, and I just feel overwhelmed by the sheer volume of parameters to deal with...Also, I'm not using any Iray products in my scene. Just basic figures, and a water plane set to 150% reflectivity. It is a dark scene of a creature entering a cave lit from within, with a dragon laying outside the cave, in front of a fire.
Best thing to do...post a render and screenshots of your render settings, light settings and a description of what, specifically, you want to achieve.
I will do that as soon as I can, mjc1016. Thank you all for the help. I really do appreciate it. Unfortunately, until the 27th of October, my internet access will be extremely limited. As soon as I can, I will post screenshots so you all can help me further. Thank you all again.
~* Phoenix DeFalco *~
Pointlights in Iray always have inverse-square fall off, so linear pointlights behave like ordinary pointlights. You reallt want to use the PM (photometric) settings which appear when you switch to iray for rendering. The Tone Mapping controls I mentioned are in their own group in Render Settings
Ummm....I really don't want this to come across the wrong way, but...Could you dumb that down a little? Could you maybe say that again using terms a little less technical? Talk like I have no idea what you are saying...Cuz I really don't...
Linear pointlights are the same as regular pointlights, the decay setting is always 2 (because that's how real lights behave).
When you set the Render Engine to Iray in Render Settings then lights get a new set of parameters that allow you to set them using real world values (Watts, for example) instead of using the abstract Inensity setting.
The Film ISO, f-stop and Shutter speed settings are in Render Settings, in the Tone mapping group on the left.
Lights in Iray behave a lot like real lights, which means that they fade away after a short distance.
when you control iray lights, you use a setting called lumiance, which is in the lower part of the parameter tab. The upper part settings of the parameter tab are mostly for use in 3Delight.
for a quick fix, you can increase the lumiance of your lights to 50.000 and see in you "see" more.
also, if you use a skydome in your render, it will block out all other lights from the sun, sky and distant lights.
are you trying to render an indoor setting? Or is it an outdoor setting?
Can you try a test render where you delete the sky dome and see if it still gives you a dark image?
Please check out this thread, it contains some useful links that might help you with some of your questions: http://www.daz3d.com/forums/discussion/56788/iray-start-here#latest
Phoenix...
In Iray two different things matter and complement each other: light intensity, and tone mapping. If you have a really dim light, just like with a real-world camera, you are going to have to increase the simulated 'exposure time' of your tone mapping. If your lights look really dim, you can boost their brightness, but you can also try increasing the exposure. Stop down to a lower f stop (try f/2.8 rather than the 8 default), or increase the ISO speed. You will see a world of difference between, say, ISO 800 and f/2.8, vs. the default ISO 100 f/8. The default is really more for outdoor work. If you have realistic indoor lighting, even a regular real-world camera would not expose properly indoors. For example, I just set my DSLR camera on auto, and pointed it down my hallway. To get proper exposure it recommended f/2.8, shutter speed 30, with my (fixed) ISO of 400 that I always ask it for indoors. And it is daylight out and sun is coming in through the windows both down the hall and behind me.
So if you are doing dim light, like a candle, just like in real life, if you want the 'exposure' to be correct, you are going to have to increase the light-gathering capacity of the (simulated) camera.
Here's some screen shots for you all...Along with the light settings I'm using and the water surface settings. Using your suggestions thus far, I have gotten the scene to finally light up. However, as a result, a new problem has come to light. (no pun intended.) I'm struggling to get the water to reflect properly. Attached is a render, using 3Delight, of what I'm trying to achieve with Iray. Additionally, I have included the Iray render as I have it now, as well as 3 text documents spelling out the Render Settings, Light settings, and water surface settings...Thank you so much for all the help so far.
~* Phoenix DeFalco *~
If I recall correctly though, higher ISO's give you more grainy results. Isn't it better to keep the ISO around 200-400 to bring in more light? (to keep this simple for the OP, the higher the ISO, the more light is let in)
Also, the Exposure Value (a few sliders up from the ISO) the lower that number, the lighter the render. Some of the sliders move together, so what I do for lower lit scenes is put the ISO around 165 and start moving the Exposure Value slider and seeing what that does, then move the F Stop and do a spot render. Then I increase the ISO if more light is needed.
TIP: Take out what you don't need in the scene, in your cave scene for example, if some of the walls aren't showing in the render, close the eye in Scene or totally delete the props which aren't needed. If you're testing lights, remove a character's hair when you're testing your lights so you'll get quicker test results.
Might not have been compatible with Iray. Some things don't work with one or the other
You should have an iray water shader that was included with Daz, I would try that on the water surface tab since iray and 3delight handle surface materials differently.
That water shader kaotkbliss is referring to is located with the Uberbase group of shaders and if I recall its under Shader Presets in Content Library
You care correct, Novica, the lower the ISO number the less light gets let in and is less grainy; the higher the number the more light gets let in and is grainier. I found a really good website, I Still Shoot Film that explains a lot about ISO, f/stops, shutter speeds and a bunch of other photography related issues in laymen's terms that were easy to understand that might help. Loads of information on this webpage. There are tons of charts on Pinterest and Google that show ISO and f/stops and what type of setting is best to use for different lighting situations. Find a one that you like and keep it handy and experiment.
edit: fixed typo "tpms pf" to "tons of" which was my original intent, but apparently my fingers weren't in the correct position and I didn't notice.
The ISO in Iray only affects the light getting to the camera, the grain that it causes in real world cameras isn't implemented. ISO 50 or 3200 makes no difference to the quality of the image only the light gathering ability.
That I didn't know. I assume then that all graininess (not sure that is a word) in Iray comes strictly from needing more render time then?