Mental Ray - Color Bleed Control?

[MegaPixel]

Just switched from Radiosity to MR last week and am still very new to it. I'm trying to understand the best way to deal with color bleeding using Mental Ray since the advanced Lighting Override material doesn't work here.

 

The attached image shows my progress so far. Any other tips would be well receieved. Thanks in advance - MegaPixel

[Guest nazcaLine]

that's exactly the same problem i have...so let's wait for someone to help us!!! there must be a special shader for this, i dont know. in the meantime, i tell you your modelling seems ok, and the ambient in gemnral is a little dark. maybe you should rise the energy multiplier value...

[lambros]

I am no mental ray expert, but I think that the global energy multiplier determines the color bleeding. In other words, I think that color bleeding cannot be controlled directly without affecting the global illumination solution. Perhaps a scripted shader would work, but the max controls do not provide anything else.

[William Alexander]

David,

 

Taking the staturation down a bit, PS or other might help. More samples...and this could be a 'keeper'

 

WDA

[DavidR]

Colour bleed in mr is usually controlled through the shader. In the mat. ed., open the 'mental ray connection' panel and unlock 'photon'. Put a photon base shader there and play with the diffuse and specular values to get what you want. It takes a bit of experimenting. I read something interesting about colour bleed in general, which said that default values give unrealistic (way too much) bleeding because your (eg) red carpet is really just a plane with it's normals pointing straight up, unlike a real carpet. You can turn down global settings, but I think a better way might be to create a shader library with the correct properties (wish I had the time!). Maxwell shaders are already set up like this, so it's very hard to do something that isn't great in it. The mr photon base thing is cool because you can do wack stuff like have your red carpet bleed green and blue checkers onto a white wall, etc. Good fun.

[MegaPixel]

So if I have a bitmap in the surface shader slot, I have to come up with an average color of that bitmap for the Photon Base in the photon slot or can I reuse the surface slot bitmap in the photon base and turn it's output/rgb settings down to 1/2 or 1/4 the original to reduce color bleed?

 

WDA, do you have any suggestions for me as to a good final render setting for a 1024x768 Final Gather of this bad boy? The one you see above was 500 GI Photons and 500 Final Gather Samples with a Mitchell Filter @ 1min - 16max.

 

Thanks guys. I'll post an update soon - Mega

 

Edit: I found this article on MR Color Bleeding a little bit after I left:

http://forums.cgsociety.org/showpost.php?p=1260272&postcount=2

[vizwhiz]

MegaPixel

 

Jeff Patton has several additional MR Tutorials at his website

 

www.jeffpatton.net

 

go To his MR pages for Max 6/Max 7

 

http://www.jeffpatton.net/Max6/index.html

 

http://www.jeffpatton.net/Max7/index.html

 

Topics include:

 

Max 6

 

IES-SUn

Lightme

MR-Color bleed

MR-Fluorescent

MR-Interior

MR-Opacity

MR-SSS

MR-Trace-depth

MR-Volume

MR-anistropic1 & 2

MR-bricks

MR-caustic

MR-dome

MR-glaremist

MR-grass

MR-Toon

MR-wire

Metallic-paitns

Photon-lights

Rust

Submerge

Volume

Water-box

Water-ring

volume-test

 

Max 7

 

other Tutorials

 

**

 

i just downloaded all of These just yesterday

and i am reading Thru Joep van der Steen's PDF

 

"Starting with mental ray"

 

Randy

[Guest nazcaLine]

let's take a look...and thanks to all of you pals for helping with MR...hope we can have more threads on MR...by the way, i have a question...i have a room with furniture and a window.i put a photometric area light (Max 7) in the window, to simulate diffuse light...i render with mr and there's good illumination, but no soft shadows on the floor, the objects seem to be floating...any suggestions to get diffuse illumination in MR? sorry for my inexperience...

[MegaPixel]

I had that problem using Radiosity and pulled my hair out trying to tweak the indirect shadows.

 

That image I posted up top uses a single Daylight System with IES sun and IES Sky. I used Log exposure control, about 500 GI Photons and 500 FG samples. The indirect shadows magically appeared and looked decent too.

 

Mental Ray doesn't support Shadow map shadows so make sure your area light uses raytraced or another supported type.

 

Jeff Patton has answered quite a few of my MR questions over at the vizdepot.com forums. He's fairly active over there these days.

 

Thanks guys - MegaPixel

[William Alexander]

OK...you got too much red, LOL

 

Yes, you can use the color bleed parts of the the shader/s interface to correct it. Even before the fancy work arounds...of course this is MY Opinion and maybe not of a sound mind-evil laugh.... there is just too much R in the RGB of your cabinet and floor material....the amount of R is controled by level of the red color component from 0-255 in your materials- the saturation- ( image maps can be adjusted in PS or the enabling the output roll out of the map, and adjusting only the R-red curves/line, in Max). If the saturation is too high, in a photoreal enviroment, compared to the real world this is what you get. Too much red is being transfered to the GI effect of the lighting. The 'lighting & GI are correct enough but there is just too much red. Especially if much of the image is in shadow, more blue and greens typically.

 

or you can color correct / balance in PS. (the red channel is like way bright )Either way you take the relative amounts of red down compared to the Blues and greens by changing its saturation/levels.

 

 

BTW you probably should up the number of FG samples a touch and emmit a greater number of photons....you can see the indivual photon hits on the cieling usally a good inciation to increase numbers and or photon size. I'd start with increasing numbers

 

WDA

[vertexART]

hi there,

as DavidR said, the best thing is to use a photon shader on the mat in question. U can control or even turn off the color bleed completely with it. But with photon shader U'll need a lot less light energy.

 

Apart from that, U should try using MR or DGS mats whenever U can. Render time difference is considerable. I've been experimenting with it after I've read it somewhere and on 800x600 simple 3000poly scene, I got 11 secs difference, only on the rendering. I am not sure about the calculation pass..

 

I just can't find the time(as always) to make a simple scene setup so we can all explore the up's and down's of MR. There is just too much about it (photon sampling, fg, lights, mats, camera shaders, light shaders, etc... ) and so little references and discussions. Thumbs up for Jeff Patton, who's made MR much clearer to wider audience.

 

hope it helps and post some progress!

cheers

[nisus]

Hi,

 

Do you use architectural materials? If so, desaturated the main color EVEN if you use a bitmap at 100% in the diffuse slot!

 

nisus

[auvn]

yes, jeffpatton make great tutorials about mental ray. One of them is about control color bleeding by Photon Base. (great)

 

Or you can search mentalray thread on CGTALK

 

 

MegaPixel

 

Jeff Patton has several additional MR Tutorials at his website

 

www.jeffpatton.net

 

go To his MR pages for Max 6/Max 7

 

http://www.jeffpatton.net/Max6/index.html

 

http://www.jeffpatton.net/Max7/index.html

 

Topics include:

 

Max 6

 

IES-SUn

Lightme

MR-Color bleed

MR-Fluorescent

MR-Interior

MR-Opacity

MR-SSS

MR-Trace-depth

MR-Volume

MR-anistropic1 & 2

MR-bricks

MR-caustic

MR-dome

MR-glaremist

MR-grass

MR-Toon

MR-wire

Metallic-paitns

Photon-lights

Rust

Submerge

Volume

Water-box

Water-ring

volume-test

 

Max 7

 

other Tutorials

 

**

 

i just downloaded all of These just yesterday

and i am reading Thru Joep van der Steen's PDF

 

"Starting with mental ray"

 

Randy

[digtlpete]

I've found that the photon base shader only seems to work for color bleed when FG is not used in the scene. Once I turn on final gather I get alot of unwanted color bleed. Does anyone have any explanation for this. I have a feeling that energy values in the lights are the culperit.

 

-Brian

[raterry]

I've found that the photon base shader only seems to work for color bleed when FG is not used in the scene. Once I turn on final gather I get alot of unwanted color bleed. Does anyone have any explanation for this. I have a feeling that energy values in the lights are the culperit.

 

-Brian

 

Can I revisit this issue? I finally just got MAX 9 and I'm playing with the new Daylight system, Low FG preset, no GI. How do I get my grass plane to NOT bleed green all around my white building? Certainly there has to be a way now to control the color bleed at a shader level? Any thoughts, it's frustrating me and since this post is close to 2 years old maybe the solution is out there and I'm just missing it.

How to control color bleeding at the shader level?

MAX 9 64 Bit, Mental Ray 3.5.2

[IceAged]

How do I get my grass plane to NOT bleed green all around my white building?

 

I have exactly the same issue and have been searching for a solution myself. The methods used in this thread seem to apply to previous versions of mental ray, (using the photon based shader), and seem to make no difference whatsoever when i try them.

Like yourself, I am using the daylight system, a large green plane for the grass, plus I have GI and Final Gather enabled with logorithmic exposure control. The walls of the building are stone, (tried both standard and mental ray materials), yet they end up going a shade of green in the darker parts of the image. Removing the grass plane fixes this, but obviously isn't a proper solution...

[nisus]

Hi guys,

 

Just popped in, didn't wanna read the whole thread... but the easiest solutions is to use an A+D material and set both GI and FG multipliers to ZERO. (The advanced rendering options tab)

 

rgds,

 

nisus

 

ps: this solution is for max9, mr3.5

[nisus]

Yup, that was a quick and dirty solution.

 

Your tutorials really look interesting, Brian. Pitty, it's deadlines just before the summer holidays... Hopefully there is some time to check them out after the holiday ,-)

 

rgds,

 

nisus

 

 

ps:No i won't do them IN my holiday... it's a holiday, not work... ,-)))

[Justin Hunt]

Try turning down the Diffuse level of the grass. In effect with diffuse level at 1 it bouncing more light than absorbing. By dropping the diffuse level causes more light to be absorbed, therefore less bleed. The side effect is that the material will become darker. Which isnt always a bad thing. You can use EC to counter this.

 

JHV

[pixelperfectg]

How do I get my grass plane to NOT bleed green all around my white building?

There's also a good discussion on that here:

http://www.vizdepot.com/forums/showthread.php?t=6388