Interior Lighting_Washout wall colours and unexplainable artifacts/blotches

[THEPRAYINGMANTIS]

Hi all,

This is my second go at an interior rendering using mental ray sun/sky and its really testing my patience. This image took 6hrs to render at low FG draft settings with GI turned on using interior exposure settings and LWF/GAMMA SETUP. The colours appear to be a little washed out or gray when they should be something else (except for the bright blues and greens). I set the colour that I want the material to be in the diffuse slot but it doesn't come out the way I intend it to. What could be causing this desaturation. Also, I can't explain the appearance of those splotches on the top right corner of the image. If anyone can give me a hand, I'd appreciate it.

[brynmor530]

Are you using Ambient Occlusion in your texture maps? If not try setting that up as it will bring out some detail. Also try using the non physical tuning in the sky and sun light settings. Reducing the colour saturation of the sky and sun should help to give you back your actual texture map colours. I'm guessing the blotches are from a either low FG or GI. Try upping the number of initial points or the interpolation. Hope that helps.

[mesht]

are you using any custom background map with the physical sky shader? i used to face similar blotchiness, so i off the background mapping, as the RGb level was set to a high value to bring out the contrast. another possibility is your Gamma settings, and the mr exposure control, what is your value?

[THEPRAYINGMANTIS]

Thanks for the responses guys. To answer your questions, all the materials have ambient occlusion switched on to 100mm (I guessed). Mr sky in the background environment is set to 0.1 to reduce glare. My gamma is set to 2.2 input/output=2.2 and my exposure is EV 8.

 

To give you an idea how far off the colours are, the bottom wall on the left hand side of the image should have and RGB value of R:188 G:157 B:129. Its called Brookline Beige from Benjamin Moore Paints. A light reddish brown and its no where near that colour. Instead it shows a light grey. I'm using a mix of Promaterials and A&D material.

 

Thanks

[mesht]

value of EV 8 is pretty wash out, normally, i would use a value of between 12 and 13 for daylighting scene, with skyportal to add additional illumination. AO value of 100mm is ok, perhaps some of your samples values are low? which causes those blotchiness

[Justin Hunt]

AO of 100mm is tiny and will result in a sharp dark line in the corners , try 1000mm or larger which will give a softer graduation.

 

8 EV for an interior is fine, try playing with mid tones to bring back some colour detail.

 

Also bear in mind the refection values of you materials and the reflection trace depth. Once the max trace depth has been reached it will return the backround colour, in this case the mr PhysicalSky. Hence the blues and greens are stronger and the others a greying out. Try changing the brightness of the backround and see if that makes any difference.

 

Post your Photon and FG settings.

 

Are you using portal lights at all?

 

jhv

[THEPRAYINGMANTIS]

Attached are my settings and yes I am using Mr Sky portals, shadow samples set at 16.

[Justin Hunt]

OK a few things to fix

 

Turn Scanline OFF, Saves a bit of memory

Reflection/Refraction Trace depth try Max trace depth 20, max Reflection 3 Max refraction 17

 

Final Gather

When using Photons set the Diffuse bounces to 0, any thing above are disregarded at render time

Leave noise filtering to standers, High takes way too long

 

Photons

 

Turn ON Optimize for FG

Max Trace Depth 20

 

jhv

[THEPRAYINGMANTIS]

Thanks Justin for your settings; it lowered the render time by about 2min. but with no significant change to render quality and the colour saturation problem still exists. Can you elaborate on what you were talking about concerning the reflectance of a material? I'm guessing this is a issue of colour bleeding from the pool water and it's affecting the wall colour and the walls maybe reflecting that colour. This is really frustrating and the long render times for a small test render really complicates the matter. It's times like this that make it really hard to love Mental Ray.

 

Thanks

[John Dollus]

Before you tried Justin's settings, did you turn off the FG Freeze?

Also, for drafts, sampling of 1-16 is too high. That's equivalent to 1-4 in Vray.

[MasterZap]

To give you an idea how far off the colours are, the bottom wall on the left hand side of the image should have and RGB value of R:188 G:157 B:129. Its called Brookline Beige from Benjamin Moore Paints. A light reddish brown and its no where near that colour. Instead it shows a light grey. I'm using a mix of Promaterials and A&D material.

 

Aaaargh, colors specified in sRGB, how I hate this.

 

Mkay, to fix your color, put it into a Utility Gamma/Gain shader. Or re-calculate it to the PROPER color manually.

 

First step is to get rid of the 0-255 range and get into the proper 0-1 range by dividing by 255.

 

Then, you raise that to the power of the gamma (2.2 in this case).

 

This meeans that your color (R:188 G:157 B:129) when correctly fed into an A&D material should be 0.511, 0.344, 0.223

 

/Z

[Justin Hunt]

Finally now I know how to convert the colour ranges, always a pain when given 0-255 colours.

 

As to the reflection refraction, when the max number of reflections are reached then the backround colour is returned. Think of a hall of mirrors where you get reflections of reflection .... Well this number controls how many reflections there are. Low numbers are quick but too low and you get incorrect reflections, too high takes very long to render but refections are more accurate and detailed.

 

Read the document on the A&D shader in the extra help for more detailed information.

 

jhv

[THEPRAYINGMANTIS]

RE: Aaaargh, colors specified in sRGB, how I hate this.

 

Mkay, to fix your color, put it into a Utility Gamma/Gain shader. Or re-calculate it to the PROPER color manually.

 

First step is to get rid of the 0-255 range and get into the proper 0-1 range by dividing by 255.

 

Then, you raise that to the power of the gamma (2.2 in this case).

 

This meeans that your color (R:188 G:157 B:129) when correctly fed into an A&D material should be 0.511, 0.344, 0.223

 

/Z

 

Hi Zap,

 

Thanks for the advice. Can you clarify that last bit of calculation? For example 188/255=0.737 what did you do to it to equal 0.511?

 

I did initially convert the sRGB values by dividing by 255 but I did not apply a Utility Gamma/Gain shader because I was under the impression that by setting input/output at 2.2 that the diffuse colour would be gamma corrected but I guess that only applies to textures.

 

Thanks again

[SandmanNinja]

I got a good tip from Bri at Mental Bout Max.

 

You can copy the RGB colour and paste it into the colour box of a A&D material and it converts it automatically.

 

No maths required and saves a few brain cells...

 

But I copied and pasted that valuable bit of info on converting!