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Thread: hdri spherical background renders dark in 3ds max vray physical camera

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    Default hdri spherical background renders dark in 3ds max vray physical camera

    I'm having a problem with hdri spherical background. When rendered through vray physical camera it renders dark. when i render it in perspective view (other than vray physical camera) it looks fine, when i increase the multiplier in material editor for vray hdri it doesn't give desired result, even when i increase the multiplier upto 100, still looks dark with vray physical camera. I tried with altering f number, shutter speed, unticking vignetting which somewhat brightened the background hdri but not like when rendered without using vray physical camera. I'm sure i must be missing something here but am not able to find out what...

    I'm working in lwf mode
    3ds max 2009 32 bit
    vray 1.5 sp4

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Try setting your dome light to invisible then put a copy of your background map in the Environment Map slot (press 8 on the keyboard to bring it up) with a multiplier of 1.

    Then in the render settings dialogue - V-Ray tab / Color Mapping rollout - untick affect background.

    Basically now your background is independent of your dome light and you can adjust each individually. This also will mean you get a proper alpha map as having the background visible in your dome light will just fill in the whole frame with a solid alpha.

    Hopefully this works for you - let me know if it makes sense.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Ah - in re-reading your question, I think I misread and have answered it wrong (for some reason I assumed you were using a dome light). Anyway you could try lighting your scene with a dome light with a hdri map in it.

    Alternatively you can put a copy of the material in your background slot and adjust its exposure in the material.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Hi Luke, thanks for reply, before telling whether it worked or not i would like to clarify my points further regarding background and lighting.

    Step 1 - In vray render setup I choose default lights off in global swithches, then in frame buffer i tick on enable built in frame buffer, colour mapping as exponential and in global illumination tab use irradiance map and light cache as primary and secondary engine. Rest settings are as default.
    Step 2- For my background setting I first go to environment and effects (keyboard shortcut 8) and from there i choose vray hdri as environment map. I open material editor window and copy vray hdri map in environment tab in one of the material editor slots as instacne.
    Step 3 - Then for extra lighting I choose daylight from systems, and in skylight drop down menu i choose none, in sunlight drop down menu i choose v-ray sunlight, when asked about assigning vray sky environment map i choose no (as i prefer to use hdri spherical map as background for animation)
    Step 4 - Then I use vray physical camera for camera with values f number = 7, shutter speed 175 and rest as default.

    Now after step 2 when i render without any vray camera the objects are properly lit as well as the background image appearing fine. But as soon as i assign vray physical camera with above mentioned settings and render i get dark image(near black), multiplying the intensiy multipliers in material editor slot somewhat brightens it up but not as what it should look like. After assigning vray sun for direct light and hitting render i can see the objects in the scene but they are dark and the background even darker. Objects and background works fine with all the above settings but with vray sky environment map in place of vray hdri.

    I tried as you've suggested with dome light as direct light source with settings you've mentioned but got the same result with dark background.
    However, when i unticked affect background in colour mapping rollout it does resulted in fine looking background as i was looking for but vray hdri spherical map was no more working as hdri spherical map but as any other background image. I tested it in my scene. Like I mentioned in stepwise manner above, after step 2 unticking affect background did result in desired background but the objects in the scene rendered pure black (so hdri image was not lighting up the scene as it was supposed to do)
    I hope I made it clear
    Thanks..
    Last edited by rm; February 9th, 2012 at 10:50 PM.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Ah - ok that gives me a better idea of your scene.

    It sounds to me like it is simply an exposure issue in the camera. I know it may sound silly, but have you tried pushing the shutter speed up a bit - like bring it up to about 50 - maybe more? A quicker answer to solve this I think would be just to untick the exposure check box in the vray camera properties. It sounds to me like your lighting is working right in your scene, its just your camera is under exposing it, so checking this box will disable the exposure and act the same as a standard camera.

    Try that and let me know how you go.

    You may find you'll get better results with your render by lighting your scene with a domelight with a hdri in the map slot instead of using the environment slot (like we talked about above), however this is just a bit of a side note and not relevant to your question.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    I've been out lately, so i'll give it a try and let you know.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    "Now when I render again, the image in the Vray frame buffer looks also very dark... This is because the max gamma preferences don't affect the vray VFB.
    Luckily, the Vray VFB has it's own gamma correction. It's the small button labeled 'sRGB' on the bottom of the frame buffer."

    Quote from: http://www.aversis.be/tutorials/vray...l_gamma_03.htm

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Use Vray physical cam. only with Vray sun and VraySky map. But if you persisit to use hdri with it you gotta boost it's value very much (like, push it from 1 to 1000, maybe more, depending on camera settings).

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    One more point would be to just play with the vray camera exposure a little, trust me that's actually what you need in your case, as it has got me to various illumination levels by putting it to (incredibly high as) 2, 4, 6 or sometimes 10, all devided by one second where 2 means half a second.

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    Default Re: hdri spherical background renders dark in 3ds max vray physical camera

    Quote Originally Posted by LukeC View Post
    It sounds to me like it is simply an exposure issue in the camera. I know it may sound silly, but have you tried pushing the shutter speed up a bit - like bring it up to about 50 - maybe more? A quicker answer to solve this I think would be just to untick the exposure check box in the vray camera properties. It sounds to me like your lighting is working right in your scene, its just your camera is under exposing it, so checking this box will disable the exposure and act the same as a standard camera.
    I've tried altering the value of shutter speed to different levels but they're not working... like you said in value of 50 it is not bright enough (actually it's dark, just brighter than previous one), i've even tried it in 5,10 but all of them are not working.
    when i untick the exposure check box like you've said, it works fine as a standard camera, gives background as i was looking for. But maybe i'm looking for everything in one package it won't give me the controls i can have with vray physical camera, one most important for me being white balance. So maybe i'll have to go one way or other.
    Thanks a lot for helping

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