Render Emitter Off showing in reflections
joseft
Posts: 310
Hi All,
I have noticed that when you set an emitter to the render emitter off setting in iray so the emitter does not show up in your render, it still persists in reflections like eyes and mirrors. I have tested it quite a bit.
I even had a scene where a building had a glass wall with a hole in it, with some emitters on the opposite side of the glass wall - if you point the camera directly through the hole in the glass wall at the emitter, the emitter is not visible. But if you turn the camera so that your line of sight to the emitter goes through the glass wall, the emitter is visibile through the glass.
Another scene i was playing around with was an interior room with a mirror on the opposite wall to the window/balcony. I had set the environment to sun-sky, with draw dome OFF. When rendering this from outside the room, i get the flat grey background which would then become alpha transparency if i completed the render and saved. If i turn the camera to look through the window/balcony from the outside of the room so i can see the mirror, the sun-sky dome is visible in the mirror still, but the parts of the render that still show the outside of the room are still grey.
I have done things differently in the past to get around this, but its becoming irritating now. Is there a way to stop this from happening other than moving emitters out of reflection range etc?
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Comments
Try going to the Parameters of the emitter and go to Display and Visible in Render; the light should still be in the render but not the emitter.
In respect to the environment lighting (i.e. dome IBL/Sun-Sky) the the texture of the dome has to reflect in mirrors otherwise there would be no light at all. All the surfaces in the scene reflect that lighting pattern to some degree (if they are receiving light at all); it's just that mirrors reflect near-perfectly and therefore you can see the light emitting image clearly. Turning dome visibility off only makes its image invisible where it would show, but not its lighting properties which will reflect in any reflecting surface.
sorry for late response - but doing this turns the light off also. Seems to be no different to hiding the light in the scene tab
In some cases, you can replace a light with a primitive such as a plane or disc of the same dimensions as the light. Apply the basic Daz Iray shader and set the emission color and intensity to your liking. Then, the trick is to set the cutout opacity to NEAR-zero, like 0.001. The shader will emit light but not be visible in a reflective surface such as a mirror. Opacity does not affect the emission intensity.
I would still like a solution to this for normal lights, as lights have some additional properties such as spread angle that are not available on an emissive shader.
Ugh! Another failing of the Daz Studio design. Now we have to use ghosted emissive primitives to light our scenes if we have mirrors in our scenes.
What does Daz Studio have to do with lighting properties on a renderer designed by Nvidia?
If you have mirrors in your scene, then you'll need to position the lights so that they don't reflect in it. Hollywood's been doing that for a century now.
not a failing of Daz Studio, but a product of using unbiased realistic lighting. In real life the light source will also show in reflections.
Light without light? Not going to happen. The closest you could get to this is turning all of the surfaces you're trying to illuminate into an emissive in a very low-light scene or through post-work. Even that "trick" of making an emissive with a primitive plane and setting the opacity to something really low doesn't always work, at least not for me. Opacity does affect the effectiveness of the emission intensity, which is why I've always had to set the lumens much higher in order to get some kind of meaningful light from them. As far as I know, they will still appear in reflections. The real trick is positioning & sizing them in such a way so that they're not noticeable.
Maybe I'm doing something wrong, but that's been my experience with "ghost lighting" in iray, so I haven't bothered with it at all.
It does work. Create a primitive, eg. a plane. Zero all reflective properties, set opacity to 0.0001 (any lower and it won't work) then punch in the emissive colour (should be white unless an actual coloured light), set colour temperature, disable two sided if not required (eg if you use a sphere or only want light emanating from one side of the plane. Adjust luminance and/or luminance units to suit.
To the op - lights will always show in reflections, even if set to hide in render. You need to use the ghost light technique.
The ghost lights don't give specular highlights so shouldn't be your only or primary lighting, best for adding in some ambient light to fill in dark areas.
My favorite method of using ghost lights is to give them 1x1 pixel black opacity map instead of fiddling with the opacity slider. Anyway, ghost lights are handy only for adding large soft ambient lightning as they indeed do not enchance specularity.
Although you can cheat the issue by using ghost lights as your primary lights and then adding very strong spotlights from the above setting the illumination type to specular only.
Be advised that ghost lights should have their geometry as light as possible. Otherwise they'll end much heavier than regular photometric lights.