Could someone clarify what's going on here? (shaders + lighting)

tcassattcassat Posts: 47
edited April 2018 in New Users


I'm experimenting with the "Sketchy" shader that applies a toon appearance through iray rendering.  I applied the shader I wanted on the surfaces and created the following image:

There is no light source in this image and the headlamps are turned off. Even so, there is standard lighting in the model (which I believe is related to the shader I applied). Okay, no problem for now.

However, when I place objects around the model, this apparently interferes with this illumination, as in the example below:


What's going on? If all the light sources and headlamps of the cameras are turned off, why do I have lighting in the scene? Is it because of the shader I applied on some surfaces? Why is the scenario interfering with the appearance of the model? Is it blocking some light source (even the scene containing no lights, headlamps, etc)?

Post edited by tcassat on


  • clmoonriverclmoonriver Posts: 37
    edited April 2018

    I know next to nothing about Iray, but based on what I am seeing and on my experience with rendering engines like Carrara and so on, I'm going to take a guess here:

    Iray probably has a global environment light / sky light / or some equivalent applied. Check your Iray render settings. What I can say with near absolute certainty is that you have a light dome / light sphere / global light / sky light applied that is illuminating the entire scene. However, once you put props around the scene, some of that lightning is getting blocked, which would, of course, be the expected behavior.

    I further suspect this is true because if you have no light sources and no headlamps in the scene, it should render as completely black. There has to be a global light sphere at play here.

    The shaders are not the issue. If you had ambient applied to some of the shaders, they would be visible even with all lights turned off. But placing objects around them would have no effect since they are emitting their own light. Not being lit from some outside source that can be blocked.

    Post edited by clmoonriver on
  • It looks to me you use notilize's high school classroom.
    If you look at the ceiling, there are lights in the ceiling that have an emissive shader applied to that lights your scene. Its called Light Bulb there. Replace that texture with a plaine white shader and also do the render settings Scene only, that will disable the hdri or sun. Once you do that everything will be black except when you put any form of lights in your scene.

  • tcassattcassat Posts: 47

    Thank you guys. You were right, the dome was lighting up the whole scene.

  • SpottedKittySpottedKitty Posts: 6,123
    tcassat said:
    What's going on? If all the light sources and headlamps of the cameras are turned off, why do I have lighting in the scene?

    You missed one — Iray also has an Environment light, and it's turned on by default. Go into the Render Settings pane, click on Environment at the bottom, and look at the settings. The default Environment Mode of "Dome and Scene" uses both the Environment light and any scene lights (whether actual lights or Emissive settings applied to an object). Change this setting to "Scene Only" if you want to turn off the Environment light.

    Note that Environments can behave weirdly in indoor scenes, depending on windows and any invisible or non-existent walls allowing light into the room.

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