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View Full Version : Blurry reflections. Mental Ray

anoon
06-12-2008, 10:03 PM
(This post is largely a duplicate of what I posted over at "The-Area" but I thought I'd try my luck here.)

I cannot seem to get decent blurry reflections no matter what I try. Looking through the help files on the subject of the Arch & Design materials, I can see that the Glossiness and Glossy Samples parameters are supposed to do what I want, but I’m not having much luck.

Details:
3dsmax 2008 64bit
Mental Ray
Arch & Design material
Sky portals
Sky light
No HDRI

Please refer to:
MR_Settings.ods (http://www.alan-noon.com/misc/MR_Experiment_016/MR_Settings.ods)
or
MR_Settings.xls (http://www.alan-noon.com/misc/MR_Experiment_016/MR_Settings.xls)
These are duplicate spreadsheets in Open Office and Excel format, containing the material settings for the metal material seen in the images linked within the docs.

Image 016d (http://www.alan-noon.com/misc/MR_Experiment_016/A_016d.jpg) is close, though a bit too smooth.
Image 016k (http://www.alan-noon.com/misc/MR_Experiment_016/A_016k.jpg) is pretty close, though too noisy.

I think I want to end up somewhere in between.

Perhaps I am screwing something up, but it seemed as if increasing the samples made the situation worse. For example:
016m (http://www.alan-noon.com/misc/MR_Experiment_016/A_016m.jpg) was rendered with Glossy Sampels set to 64. Lower samples seemed to look better. Also, render times were insane at 47+ minutes!!! (I work in games, so I am used to a frame rendering in 1/60 of a second. Is this normal? A 2 minute render is almost unbearable!)

I guess what I really want is a way to control the glossiness the same way I would do it in realtime: with a mask. White being shiny, black being not shiny, and grey being some degree of matte-ness inbetween.

Any suggestions?
Riffmaster
06-13-2008, 05:36 PM
The general rule of thumb with regards glossy reflections is the more blurry you want the reflections the more samples you need.

A perfectly specular surface would have a glossiness value of 1.0 and a perfectly diffuse surface a glossiness value of 0.

Having glossiness values of over 64 samples is not unusual it can depend on the resolutions you are rendering to but obviously be prepared for huge increases in render times.

However for view 016m 47 mins sounds quite a steep render time what resolution and spec machine are you rendering?

View 016d this looks as though you are using the fast interpolate mode checked?

You can interpolate the glossy reflections that can greatly improve render times although it can mean playing around with the settings quite a bit.

There is some really good max help files relating to these settings.
anoon
06-13-2008, 08:29 PM
Thanks for the response David.

I have to profess that I am very inexperienced when it comes to offline rendering. It took me a long time of fiddling with all manner of settings and configurations before I finally got the general color and contrast of the scene. I would not be surprised to find that I have set things up in some fashion that is technically "wrong" and now my sampling increase is working conversely as to how it should. I have not posted up the latest render yet, but last night I rendered version 016n with 200 samples and it looked even worse and took 3 hours to render.

At this point, i think i need to scrap the scene and start over.
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06-13-2008, 08:29 PM
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