Properly applying emissive shaders to make objects give light
Hi. It's me again.
On my earlier post someone made mention of using Iray's emissive shader to a computer display to make it give off light rather than faking the effect with different lights that I'd then have to make invisible for my render.
How the ()*&$%@ do I do that?
I'm using the Sci-Fi Screen from Phantasmagoria. I've been able to highlight the glass display portion of the screen, since I don't want the posts glowing. I select Iray's emissive shader from My Daz3d Library>Shader Presets>Daz Uber>Emissive.duf. With the glass still selected, I double-click the shader and the entire thing turns white. No big deal. I just adjust the emission color to what I want and we're good. However, my figure is crouching directly in front of the screen and should be illuminated by it. When I turn the camera's headlamp off, the screen seems to be glowing in the proper color but it doesn't emit any light toward the character.
What's the magic word to make the screen give off light? Do I need to apply a different shader before or after the emissive shader, or is there a setting in the editor pane I have to tweak?
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What are your render settings, under environment? What are the settings on the glass under Emissive colour?
I set it to 175,000 lumens and got nothing. Do you have better results by candles per square meter or foot?
My environment tab reads, in order:
Environment Mode: Scene only.
Environment Intensity: 1.00
Environment Lighting Resolution: 1024
Environment Lighting Blur: Off
Ground Position Mode: Auto
Draw Ground: On
Ground Shadow Intensity: 20
For the glass, I have its color set as 0 1 1 (one of the light blues offered in the palette rather than a custom color). I haven't adjusted any of the other settings yet.
Two possible problems I can think of...reversed normals....that would make the light go the wrong direction. The second..if there is a glass surface and an 'image' surface...turning the under surface into an emitter and not making the glass thin wall.
Is Two Sided light selected in the Emission settings as if it is the Normal direction won't be an issue. If that is OFF try turning it ON and see if it emits light. If it does then you need to flip the normal direction using the Geometry Editor Tool located in the Tools menu. Also is the scene enclosed in a building or structure as if it is you may want to think about adjusting the tome mapping to suit the environment. See photography sites for more on that side.
I checked the properties on the screen and saw that the option for "two sided light" was on, so that should be good. The option for "thin walled" is on, too.
As far as environment, I've left it as illuminating "scene only" and so far these are the only objects I've added. I wanted to get the screen's glow ironed out before I had to fight with the scenery's native lighting or presets. This is how the scene renders in 3Delight; Iray comes up black. The headlamp is off in both of them since I want the scene's only light to be coming from the screen.
3Delight thinks part of the frame should be glowing while Iray doesn't. No idea why one does this and the other doesn't when the few settings they have in common are unchanged.
Another question: does the Iray emissive shader actually cause an object to glow? If it does, would its opacity matter or what it's made of?
In Iray go to Tone Mapping and change the camera settings to Shutter Speed=1, F/Stop=1.4, ISO=400 and I set White Point to 0.96. You can play about with the Speed/F/Stop/ ISO settings if it is too bright/dark.
Someone will say you don't need to set them all but I'm a photographer and that is the way I work
You should simplify your setup to hang of it, and avoid the variables.
Start first with a simple plane primitive. Add it to your scene, then apply the Emissive shader. Be sure to use the shader as opposed to just flipping on the Emission color; the shader it zeros out all the other settings that could compete with the emissive property. Start cranking up the Luminance, and play with the Luminance Units. Experiment and discover how things work.
Unless the screen in your scene has a special shape, you could just as easily use the plane primitive for your screen. Place it where you want the screen to appear. This will eliminate any issues related to the geometry of the mesh in the screen you're using.
If you want a glowing image on the screen, add the image to the Emission channel - click the arrow, and select the image you want. You may need to crank up the Luminance even higher if the image is on the dark side (the control panels on Star Trek TNG, for example).
Finally, consider what you're doing no different from making a movie. Despite using a physically based renderer, you're recreating the appearance of reality for the purposes of telling a picture-based story. In the movies, they'd use a projected prop, like what you're trying to set up, but they'd also add lights around the set to make it more interesting to the audience. Using their skill and creativity, the crew would make it look not only real, but better. You need both -- real and better. Just because you "can" light a scene just from the monitor, doesn't mean it'll make for a good picture.
It rendered as completely black, even after applying the emissive shader to the primitive panel I added to the scene. Fiddling with the tone mapping is a trick I'll have to file away for future reference, though. But much, much later!
Would you believe I tried that already? I can't get any illumination from anything using the emissive shader. I took the luminance up to 300,000 lumens and got nothing. Even though the switch for two-sided illumination is on (which I think means light comes from both faces of the plane) I can rotate the plane 180 degrees and I still get no light from it.
My fault for not making myself clear. I'm not trying to illuminate an entire scene with just the monitor. I'm adding the monitor first to see if I can even make it light up before I add scenery lights. This is my attempt at some kind of realism; even with environment lights, there's going to be some kind of glow from the screen, so I was trying to get a good look at how the screen could be illuminated before other lights interfered with it.
These are all helpful tips and I'm grateful for your help, but I'm starting to think Iray just doesn't like me. Even when I create a primitive light from the toolbar--plane, sphere, or whatever--Iray doesn't recognize it as a light source. Is there a way to force Iray to see planes and cones as light sources, or are these restricted only to use as shaders?
Yes, it sounds like Iray hates you!
Would it be possible for you to take a top and bottom screenshot of of the shader in question? That would answer a lot of things. And I also want to reiterate that you need to apply the emission shader, then not touch it except for the emission settings toward the bottom. (Trying 1 or 2 sided is a good idea, too.)
The Tone Mapping settings are for lowering or increasing the overall scene brightness. A very low setting as proposed can help if you're trying to render just from the emission source, but as you're not doing that -- and Iray generally prefers more photons to work with -- start from a standard setting, so there are fewer variables. Then alter the emission settings to match your scene, and then if you need to, tweak with Tone Mapping.
Though Tone Mapping doesn't (yet) affect the quality of the render (setting a higher ISO doesn't introduce film grain, and changing the f-stop in the Tone Mapping channel doesn't alter depth of field), you might as well pump more light into the scene. The actors won't mind, and there's no extra cost in renting more lights.
I’m starting from scratch here and duplicating what I’ve done on the other scene. This way there is no confusion or clutter to deal with. All my Iray and 3Delight settings have been set to default except where shaders have modified them, although I have turned off the camera’s headlamp. I have it set to render “Scene Only” so I don’t have interference from Iray’s outside sources and I want the scene lit solely by lights in the scene.
With the figure in a black environment, I went to “Lights” on the right side of the console and picked “Light Plane.” I positioned it to the figure’s right and left the headlamp blocker on the ground where it appeared. Although the plane is listed as a light, I can’t modify it using the “Light” tab, so I went to “Surfaces” and found the emissive shader. When I selected the plane, the emissives tab blanked out and I couldn’t select anything else. From the left side of the console, though, I applied the emissive shader to the plane.
Back to the right side, I stayed on Surfaces and went to Ambient to pick my color. Now the plane is the color I want. So far, so good. “Light” opened up to show me “Basic” and “Falloff.” I noticed that Falloff is turned off. I turned it on because I remember from another session that this controls how fast the light fades the farther it gets from the source. I was afraid it was falling off immediately or something, so I set the start at zero and the end at 100. The intensity and other settings are otherwise set at their default.
And this results in an all-black render. I spun the plane 180 degrees and got a black render again. If I didn’t get you the screenshots you need, let me know where to look and I’ll find them.
Thanks for the help!
The settings you have there don't look like iRay settings so this would yield a black render - I've taken a picture of the emissive settings I used with the resulting render as well, also sent you a PM.
I have a big render running ATM but I set it to run on two cores and set this scene up on the other two and rendered it.
The light is coming from the row of LED's on the left and the big panel in front using the Emissive Light shader. LED's are 5 watts at 0.5 efficacy 1500 K temperature and the panel glass is set at 5 Watts at efficacy 5.0 7500 K temperature and a random .jpg from the scene files.
The camera in Tone Mapping is set to Shutter Speed 1.0, F/Stop 1.4 and ISO 400, white point 0.96. Environment is scene only.
You are using a 3Delight area light, not the Iray Uber Shader - look at top-left of the Surfaces pane in your screen shots.
Even is you where rendering in 3Delight those settings for the UberArealight wouldn't throw much light because you have the fall off distant set to just over 2 CENTIMETERS.
Yep, this is why screen shots are so important! As others have said, in this case the Iray Emissive shader is not being applied. Here's a foolproof method, if you follow the steps:
1. Add a Plane primitive. Position and size it.
2. Select the object in the Scene tab.
3. Go to Surfaces tab, and select the object and any surfaces (your plane will have only one).
4. Apply the generic Iray Uber shader. This is an extra step just for verification. You will see the shader settings change. If you see Ambient, it means the Iray Uber shader was NOT applied. There is no Ambient channel in the Iray Uber shader.
5. Now apply the Emissive shader. Some of the settings will change. The most notable is that the Emission Color will go from black to white. This is important! Verify that you see this change. It shows the Emission shader was properly applied.
6. Alter the 2-Sided light, Luminance, Luminance Units, and Emission color settings.
You mentioned before that you experimented with setting 2-sided light. This is only a setting for Iray, so obviously in the past you've applied the Iray shader, just not in example screenshots. So try again with the above steps.
As I had it set up I did a few more renders. Images 1,2 and 3 I added extra lights. The environment is Level 19 and there are lots of lights dotted all round
First I added Emissive Shader to the column lights in Image 1.
I then added the overhead lights in image 2.
I pulled the camera out for a shot to show all the lights. The Tone Mapping camera settings in these three images are all the same as the original image in the previous post.
In image 4 I changed the Tone Mapping camera settings to Shutter Speed 1.5, F/Stop 4.5 and ISO 400 to tone down the lights and get a bit more shadow.
Image five is the last image showing all the lights with all the Tone Mapping camera settings set to default.
Then we have identified another problem. Somehow, after selecting Iray and playing with the settings there, DS keeps switching me back to 3Delight somehow. All the selections I make for shaders are under Iray tabs and under Render Settings I have Iray selected. How do I make Iray the default renderer?
Next question: no settings here are letting me use the light plane as a light source. I can only adjust the falloff on light sources like spotlights or point lights. DS is only letting me use the plane as a surface shader or something, because the settings I see for lights don't appear here and if I have the object selected, I can't even open the Lights tab. And how the heck could you tell falloff distance in centimeters from the screenshots? What were you looking at so I can watch for it later? (I still don't know everything I'm looking at.)
Are you sure you had both the surface and the object selected when you applied the emissive shader preset?
Yes, sir.
But after careful deliberation and having consumed half a bottle of Tylenol in a vain effort to mitigate the headaches, I have decided that Iray is more trouble than it's worth and I'll stick with 3Delight and numerous workarounds rather than wasting time with Iray. The advice and effort on everyone's behalf is greatly appreciated, and thank you one and all for your time.
See you folks around the forums!
If possible, I'd like to posit a slight takeover of this thread to adjusting our results for what we get when we do properly apply the emissive shader.
Side note: Fishtales' suggestions went a LONG way toward my getting my emissive renders to work properly. Thank you so much.
I'd like to offer up to the table my "Alice's Adventures In IRay" piece, found in my gallery over here: http://www.daz3d.com/gallery/#images/209271/
As you can see in the description, I'm happy with a lot of this image. However:
*The jewels and fingernails aren't being "beacons" like I'd prefer them to be. They seem flat, and I'd like them not to be.
*I have the reflection settings turned up to the maximum they can be for her eyes and the lights are still not coming up as much as I feel they should.
*For some reason, I can't get her earrings to be a cooler white - they come over as a warm white, casting that yellowish tinge. Not sure how to get that cool, blue-white light (and yes, I tried applying a slightly different "white" off of my pallette - no dice)
Would getting and using the DG IRay Sci-Fi set help me get what I want, here, do you think? Or perhaps something else?
I'm open to suggestions and critiques, here. I want to use the emissive shaders to their full potential, and I honestly can't wait to get the most out of them.
I suspect that you need to increase the level of luminance amount if you want it reflected by the eyes. You also should check the color temeprature on the earings and see if they are lower than 6500. If so change it to something like 7200 and see if that does not cool them out.
Right now, the lumens on the earrings, the nails, and the jewels are all set to 75k, but the color temps have not been touched. I'll give that a shot and see what I come up with.
Thanks!
The light emmission coming from those pretty much guarantees they will look flat in your renders - if you want them to appear to be lit relative to the rest of the scene but still retain their geometric scape they need to be much more reflective and smooth compared to the rest of the scene and off scene lights placed that will be reflected off the objects. You will have a hard time causing two different color lights to be reflected off those objects so close to one another.
The alternative is you turn down th emission of light from those to be about 1 w and then the geometry of those shape may be visible, but still probably not. That is not enough to light too much the rest of the scene without making them very shiny and oily and smoother than is typical.
I have reflectivity on the nails turned WAY up, but I don't know that it works while the emissive is turned on. I've spent the whole night fiddling with temperature and lumens, though, and I have the earrings where I want them, finally.
I'll play with the rest later. :)
But off hand, what settings would you suggest, Nonesuch?
Strange... "two-sided" so far often turned emission OFF for me - Any idea why that could happen?
( Actually, I would have expected it to do what you said, but somehow it usually didn't
... )
Darker colors don't put out as much light as lighter colors, so if you are still at 75K for the blue and red, don't be afraid to double it, and keep moving it up. Making the surfaces light emissive does pretty much kill any reflectivity, yeah.
Yeah, I'd been noticing that. Which kind of sucks, because I had a thought that putting some metallic flake components into things would give a really great light profile when all was said and done.
150k lumens seems a bit much to me, but I'll give it a shot and see what I can come up with. If it looks good enough, I'll post it here in the thread.
Thanks for the help and input, folks. Really appreciate it, please keep it coming. :)