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Turn off cast shadow of walls in Iray

Member_257874Member_257874 Posts: 76
in The Commons

Hello

I understand, that Iray emulates physical lighting, however I would like to have a room where a ceiling or a wall is not casting shadows. In 3dlight I turned cast shadows off for the parts when I used a diffuse light source, but I can not find that option anymore. When I put a figure into a room and render it in Iray, I always get the head lamp or a dark image because the walls are blocking light from HDRI image. I made my own HDRI and thought I could use it as a diffuse light source for Iray (just a grey image with a bright spot at one side).

Is that somehow possible?

Comments

  • AllenArtAllenArt Posts: 7,175

    To my knowledge, it's not possible to do that in Iray.

    Laurie

  • FishtalesFishtales Posts: 6,212

    If you want diffuse lighting in the room then select the ceiling in the Scene Tab and go to the Surface Tab and turn on the Emissive option, put the ceiling texture .jpg in the colour option, set the temperature to give the colour of light you want and set the Luminance low to the level of brightness you want.

  • Member_257874Member_257874 Posts: 76
    Fishtales said:

    If you want diffuse lighting in the room then select the ceiling in the Scene Tab and go to the Surface Tab and turn on the Emissive option, put the ceiling texture .jpg in the colour option, set the temperature to give the colour of light you want and set the Luminance low to the level of brightness you want.

    hey thanks for the advice I will try that

  • Member_257874Member_257874 Posts: 76
    Fishtales said:

    If you want diffuse lighting in the room then select the ceiling in the Scene Tab and go to the Surface Tab and turn on the Emissive option, put the ceiling texture .jpg in the colour option, set the temperature to give the colour of light you want and set the Luminance low to the level of brightness you want.

    Hm I just tried to find that emitter option but I couldn't find it in the surfaces tab. The ceiling has an emitter like default primitive. How do I create this?

  • fastbike1fastbike1 Posts: 4,078

    The ceiling needs to have the Daz Iray Uber shdare / emitter shader

  • Silent WinterSilent Winter Posts: 3,875

    Or use a ghost-light (a nearly invisible plane with the Daz-Uber Emissive shader applied and ramped up to the correct brightness) - create plane, scale and position (flip over for a ceiling so the 'top' is pointing down) - apply Daz-uber emissive - change lighting to temperature 6500 (white light - higher for bluer, lower for redder) - change lumens (intensity of light) to kcd/m2 (instead of cd/m2) makes it 1000 times brighter - then set the number to whatever you need - start around 1000 and adjust from there - then set the 'Cutout Opacity' to 0.0001 (if it's zero, there'll be no light) - render.

    Using the actual ceiling and texture map is better - but the above should be faster to render.

  • ToborTobor Posts: 2,300
    edited August 2017
    mindphuk_566386ef79 said:

    I made my own HDRI and thought I could use it as a diffuse light source for Iray (just a grey image with a bright spot at one side).

    An HDRI with a gray background and bright spot isn't a diffuse source. Assuming a 32-bit image, you'll get a shadow if the light strikes a subject. Is this what you want or not?

    A) If you want more realistic lighting, try hiding the ceiling, or sliding if off a bit to let the HDRI light come in. You can augment this light with emissives or scene lighrts, like spotlights.

    B) An emissive light source will be truly diffuse, which tends to not be as realistic. I see a lot of renders posted here that use this technique and the image is ruined. There are ways to make fully diffuse lighting look good, but it's harder than just using a nice HDRI and hiding the ceiling. In any case, if this is your aim, you can use the emissive plane technique. I'd recommend the following as alternatives to what you might read in threads on this subject:

    1. Apply the Iray Uber Emissive shader, as noted.

    2. Change the Emission Color to what you want -- white, off white, whatever.

    3. Dial the Color Temperature to 0. When you do this, the color of the light is only set by the Emission Color channel.

    4. Set the luminance units to cd-cm2, which is candles per centimeter square. This conforms with D|S's default units of measure.

    5. Use a smallish starting value for luminance, maybe 300 to 1000. Because you're using cd-cm2, you don't need high values.

    6. You don't need to set the Cutout Opacity (the value of 0.0001 is correct) unless the ceiling or plane is visible in the camera.

    7. Set Tone Mapping to the default values, and do test renders. Adjust the luminance until you get the overall brightness you want.

     

    Post edited by Tobor on
  • BartlebyBartleby Posts: 57

    If you want to make a wall invisible, there is a tool to do that just for this sort of problem. Unfortunately I am in on holiday and can't remember what it is called. 

    It is under the Create menu , something like Section Plane. Or <something> plane anyway. Once this plane is in your scene everything to one side of it is invisible to the renderer so just drag it next to the wall you want light to come through. 

  • kyoto kidkyoto kid Posts: 41,857

    ...if you switch to Iray Interactive mode, you can then turn off shadowcasting by selecting  "Shadow: None" in the light's parameters tab.

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