Black Spots of Death: "Black Holes" in Renderings

[jeremyvandyke]

Hi all,

 

This is a recurring problem that has been popping up in my renders lately (2 images attached). Black spheres appear in reflective surfaces in my scenes, and they seem to be roughly related to the photometric lights that I have placed in the scene. They appear under all settings, though the appearance changes somewhat if use Global Illumination, Final Gather, or a combination of the two. I assumed that there was some sort of interference from the light object itself, so I checked the settings and found one setting to make sure photons "pass through" the light object, but that has not made a difference. Is there another setting within the light itself that could be causing this problem? I used to use standard lights almost solely in my scenes, and I have never encountered this problem before, so I feel that it is likely an issue with the lights themselves?

 

The reflective surfaces that are giving me trouble are "standard" materials, with a reflect/refract map in the reflection slot. I have also tried raytrace reflections and have received the same result.

 

Has anyonme ever had this issue before? Any hints / tips how to make this problem go away? Thanks Everyone!

[Scott Schroeder]

Mental Ray doesn't really like standard materials, no renderer outside of scanline really plays well with them. You should always use materials that are native to your rendering engine, they are optimized better. So if you are in mental ray, use arch and design.

[jeremyvandyke]

Scott,

 

I switched out my glass and created a new glass material with arch. and design materials. I got a much more sensible "white spot", a hot spot resulting from the adjacent photometric lights. Do you have any tips from getting rid of these hotspots? On my higher qulaity versions of this render, the output of the lights in the scene are actually quite close to what I need for the final version - if I reduce their output too much to avoid the hot spots, I will dull the scene. Do you have any suggestions? (dim the lights, up the GI, are there some exclusion settings I could use on the glass objects themselves?). OH this brings up one other big thing that I can't seem to fix with my MAX at the moment. When I go to any object's properties by right clicking "object properties", nearly all of the possible options are black out except for "hide/freeze". All other options such as rendering control are not at all available. This is extremely frustrating as I am trying to eliminate some objects from casting shadows etc, and for some reason, the option is not available for me. Is there some setting elsewhere in MAX that is overriding my ability to use these options?

 

Thanks,

 

Jeremy

[Scott Schroeder]

It looks like a reflection of your light. Set your light to not be visible in reflections and it should clear up.

 

It could also be a specular highlight. Try adjusting your glass material to not have such a broad specular falloff or uncheck affect specular in your light.

[jeremyvandyke]

Scott,

 

I have been trying to turn off the visibility to reflections off in the light's "object properties" rollout, but for some reason, all of the options in the "object properties" rollout are grayed out (can't manipulate them for some reason). This is the case not just in my current model, but any new model I create with an entirely new session of max. Object Properties is not working just for lights, but all objects. Is there some other setting in max that would prevent use of the object properties rollout? I can't find anything about this problem in forums or in MAX's help.

 

Thanks again

[Corey Beaulieu]

Try clicking where it says "By Layer" It should actually say "By Object"

 

They look like lables.

[Scott Schroeder]

It's not a problem or a bug. In your object properties, it should now say "By Layer" Click where it says that and choose "By Object" and you'll get your controls back. If you want to set it to default "By Object" go to Prerference -> Uncheck "Default by Layer for new Nodes"

 

Or, you can control your settings by the layer properties in your layer manager rather than object properties.

 

EDIT: Yeah, what Corey said.

[jeremyvandyke]

Yeah that definitely was it... Not sure why that wasn't a roll-down menu like everything else, but thanks for your help guys.