Mental Ray color bleeding

[Brett]

I am creating an interior scene with MR and I am getting a lot of color bleeding. Is there a way to control how much color is bounced after a photon hits a surface? I am thinking of how you contol color bleed in the Radiosity engine in max - just dial down a setting?

 

Thanks

 

Brett

[Tommy L]

You can alter the settings in the advanced lighting override rollout in the material editor. This way you can control the colour bleed, strength of light bounced etc by material. Id advise you read the help on the subject though, as the terms used can be a little misleading. Good luck!

[Brett]

You can alter the settings in the advanced lighting override rollout in the material editor. This way you can control the colour bleed, strength of light bounced etc by material. Id advise you read the help on the subject though, as the terms used can be a little misleading. Good luck!

Tom

 

Thanks for the reply. I believe the rollout you are referring to only applies to Radiosity rendering and not to Mental Ray rendering. I would be very happy if you can prove me wrong.

 

Thanks again

[bio2000]

Hi there, sorry for hijacking this thread but i have a similar problem with MR. I think i've tried to read everythung i could about MR and GI/FG. Thanks to jeff Patton i found out alot of useful things. Thanks alot for that. Actually i am trying to light an interior scene for trying to get some descent results but i have a significant problem!!! The thing is that my floor is emitting ALOT of light and bounces ALOT of coulour (my walls too, but not so much) maybe my light reflectance is too high in my scene, but if i put them below 5 my scene is really dark so i pushed them to 15 (the "max Trace Depth" option under Indirect Illumination in 3dsmax6) i tried to exclude my floor from the GI calculations but it gets all dark

 

i also had to push the GloblaLight to 125000 and lower the decay to 1 !!!

 

What the hell am i doing wrong?

 

p.s. see the images for a before/after turning GI on and off on the floor!

[Brett]

Hey, Luxembourg!

 

I don't think I've encountered anyone from Luxembourg before - cool.

 

 

I have learned a lot since I posted this – I have found that it is a very difficult balancing act. The best way to figure it out is to create a VERY simple scene. Flip the normals on a grey box and create a bright red box inside. Then light with a single spot light. Start with MR default settings and start to play.

 

I found that you should use either an architectural material for architecture or use a MR material from scratch and adjust the photon channel with a basic photon shader. It seems that no matter what you do in final gather you are going to get SOME color bleeding. You just have to live without complete control:-)

 

Try to keep the settings on each surface, floor,walls,ceiling, consistent in terms of the amount of their reflectivity. Once you have turned down the color bleeding with either the Architectural material or the basic photon shader (pull down diffuse and specular to control how the photons react when they hit the surface) you will have to adjust up your lighting. Basically it is a balancing act between how reflective a surface is with how much energy is in the scene. By default surfaces will be very reflective so you have to one way or the other turn down how much light is being reflected and increasing the overall energy in the scene.

 

Keep things as simple as possible and try things one at a time.

 

Nice renderings by the way –

 

Brett

[bio2000]

Hey thanks for the fast reply

 

I didn't even think about using the Architectural Material. I think i should try that!

 

Btw: Does the color bleed scale or reflectance scale do the trick?

 

cheers from luxemburg!

[Brett]

It does - in final gather it can totally eliminate color bleeding from one surface to another. Dial down the "color bleed scale"almost to 0 and reflective scale - maybe between 35 and 85 for most surfaces. 100 in the reflective gives very unrealistic results becouse no surface reflects 100% of all light. walls are around 45-65. However, I believe when you do a final gather it will always grab a little of the ambient color of these scene - meaning it is very difficult to get a totally white material. There may be a way around this but I have not found it yet.

[bio2000]

I finally tried to do some render with ArchMat. and the result lokks kinda ok, but i still have some light splotches here and there and i really don't get it!!

 

are these light leaks due to that my object is not one single object (just boxes stuck one into another) ?? Or am i missing something here??

 

i just took an grey override ArchMat to test my scene without textures and such:

 

p.s. the second one was just a test with some archmats AND textures!

[Brett]

It is one of two things. You either need to increase the “quality” of the rendering meaning turn up # of photons or samples or something like that. More likely it is the material on those objects that are reflecting too much light. Try either using an architectural material on them as well or use a standard MR material with the basic photon shader in the photon channel. Then adjust. I played around with this more yesterday and it was looking great. I don’t think it has anything to do with your modeling.

[Cesar R]

Bio2000,

 

can we have an update on your scene?