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mental ray interior rendering; very dark ceiling.
show user profile  Nanne
Here's a test render of a kitchen I'm working on. I'm having some issues with the ceiling being fairly dark. The walls are white but the ceiling is very dark, but it is the same material.

I'm using the Daylight System and two Sky Portals (located "behind" the camera in this render), FG + GI, with the Photon Target of the Sun to direct the photons. I've boosted the GI Photons of the Sky Portals, 250 times (tips from Jeff Patton). I've tried using Ray Type Switcher to make the floor return white FG and GI rays, but it makes no different. I also tried to use the Photon Basic Map to control the GI colour. Booth are tips from Jeff Patton, but it makes no different for me.

Any tips on how to force more light onto the ceiling?

Kristoffer Helander
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read 1950 times
2/7/2012 12:16:05 PM (last edit: 2/7/2012 12:16:05 PM)
show user profile  Stianbl
Lighten the material, or render with linear workflow..
(gamma at 2.2)

read 1937 times
2/7/2012 12:40:48 PM (last edit: 2/7/2012 12:40:48 PM)
show user profile  Nanne
I am working with linear workflow and the walls are bright enough. It seams to be the indirect illumination in the ceiling that's the problem.

Kristoffer Helander
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read 1934 times
2/7/2012 12:53:41 PM (last edit: 2/7/2012 12:53:41 PM)
show user profile  mike_renouf
Looks to me like your lighting solution could be heavily interpolated? What FG and GI settings are you using? The ray type switcher hack is best used for getting rid of colour bleed so I'd suggest you don't need it here. As for the 250x portal photons I've never needed that. Are you using physical units?

read 1922 times
2/7/2012 1:25:00 PM (last edit: 2/7/2012 1:25:00 PM)
show user profile  Nanne
I've been doing some more test renders and the Ray Type Switch hack doesn't effect the image at all :P And I don't see much difference between the 1x and the 250x GI Photons rendering either.

Yes I'm using physical Units. FG is set to Draft (I've also tried with Medium)
FG Point Density: 0.1
Rays oer FG: 50
Interpolate over: 30

Maximum Num. Photons per Sample 500 (also tried 2,000)
Maximum Sampling Radius: disabled
Merge Nearby Photons: disabled
Optimized for Final Gather: checked

Average GI Photons per Light: 200,000
Decay: 2.0
All Objects Generate & Receive GI and Caustics: checked

Here is another render with the wall/ceiling material set as Material Override:

The ceiling is still just as dark, so it doesn't seam to be a problem with Colour Bleed from the floor, as I first expected.

Kristoffer Helander
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read 1912 times
2/7/2012 1:48:52 PM (last edit: 2/7/2012 1:49:12 PM)
show user profile  mike_renouf
In all honesty I dont see that your ceiling is unnaturally dark in the first image. But I do think that the lighting looks a little too smooth. Interpolation settings seems fine.
I learned recently that increasing the trace depth of photons has a really beneficial effect in my scenes. Bumping reflect and refract up to 10 or so and the photon trace depth to 20 means the GI solution is far better.
For FG turn off the noise filtering. If your FG solution is lumpy then increase interpolation points.

Are you using AO in your materials? Something looks very odd around the doorway on the right of the image.

read 1904 times
2/7/2012 2:05:18 PM (last edit: 2/7/2012 2:05:18 PM)
show user profile  Nanne
Thanks for the tips, I'll give it a try :)

Kristoffer Helander
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read 1901 times
2/7/2012 2:12:18 PM (last edit: 2/7/2012 2:12:18 PM)
show user profile  Nanne
Here we go; I set the all of the GI Trace Depth values to 20 and the other Reflections/Refraction Trace Depth to 10. I also set Noise Filtering (Speckle Reduction) to None for FG.

This images is with a cleaner A&D material without bumps, or AO. I think the bright halo by the door in the back is due to light leakage. The "door" is just a box to block the light, I haven't made the door yet :P

And here's the render with the original materials again, with the settings mention above.

Not much difference to be honest. But do you think it looks correct Mike? I'm not really satisfied with it from a artistic view, I think it steal to much attention due to the high contrast between the walls and the ceiling. But perhaps this is better to fix in post.

Kristoffer Helander
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read 1884 times
2/7/2012 3:06:55 PM (last edit: 2/7/2012 3:06:55 PM)
show user profile  herfst1
I preferred the first render. This one looks extremely bland. I would like to give suggestions but I'm a complete noob when it comes to rendering and lighting.
read 1875 times
2/7/2012 3:37:37 PM (last edit: 2/7/2012 3:37:37 PM)
show user profile  mike_renouf
Yeah, the door is causing light leaks for sure.
I'd suggest that you need a direct light source of somekind. Your portal lights provide illumination from the sky, but with them alone it's like a really bright foggy atmosphere outside is giving you an eerie glow. There's no direct light so you don't get any shadows per se. Add a sun or a direct light source to simulate one.
Just my 2 cents.

read 1875 times
2/7/2012 3:55:39 PM (last edit: 2/7/2012 3:55:39 PM)
show user profile  Nanne
Hm, yes I see your points there :) I'll look into it! :)

Kristoffer Helander
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read 1857 times
2/7/2012 5:09:23 PM (last edit: 2/7/2012 5:09:23 PM)
show user profile  Mr_Stabby
the ceiling is fine, its just the walls and furniture that is too white in relation to the floor. For regular materials never use diffuse brightness higher than 0.75, otherwise some surfaces gather more then 1.0 luminosity which will be cut down to 1.0 but only after the effects have already been translated to other surfaces making everything look unrealistic.

read 1841 times
2/7/2012 6:39:16 PM (last edit: 2/7/2012 6:39:16 PM)
show user profile  mike_renouf
Have a read of this "making of". I learned masses of useful techniques and tips from it, including the one that Stabby rightly pointed out:

read 1835 times
2/7/2012 9:17:58 PM (last edit: 2/7/2012 9:17:58 PM)
show user profile  Nanne
Thanks for the tips guys, I'll look into that :)

Meanwhile, this is what I've got this far, I've done some work in post. I cropped the image because I think it made an improvement, to some extent. The ceiling was almost 1/4 of the previous images, thus stealing a lot of attention. Now the kitchen area looks smaller and more believable in scale, I think.

What do you think?

Kristoffer Helander
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read 1814 times
2/8/2012 12:28:16 PM (last edit: 2/8/2012 12:30:29 PM)
show user profile  herfst1
I think you might need to work on the marble granite counter. The material looks very tiled especially at the left most side of the screen.
read 1807 times
2/8/2012 1:05:16 PM (last edit: 2/8/2012 1:05:16 PM)
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