Vray Glass Problem

[Hallock]

I'm using VRay 1.46.10, and I've noticed a problem with a simple glass material. I generally work with exponential color mapping, but this is a huge problem. I've set up an entirely default scene, the box shown has a glass material with refract at 255,255,255. The only other thing is that I have affect background turned off, yet when I render in exponential the glass is darker and I don't know how to fix it.

 

Any help would be greatly appreciated, here are pictures of the problem.

 

[Craig Ramsay]

Can you post your material and lighting settings?

[wcraig]

I am not sure how to fix your problem, but some things I would try are: See if in your G buffer settings checking affect background on or off has any effect, Play with the amount of "max depth" rays in your reflection and your refraction, more so probably in your refraction, and try changing your exit color to white, and just in case your fog color as well, even though you will lose you color. Also check affect shadows in your material as well.

[JamesTaylor]

i would have thought the glass is darker simply because you are now using an exponential curve for your exposure control against the previous linear control. This will make the same light levels appear different.

 

Unfortunately its not the easiest thing to explain, but in a linear fashion, if you have white at the bottom level and black at the top level 50% along the linear line will be an exact middle gray, hence it being linear.

 

on the other hand when the same scale is turned to exponential the graph line now curves so 50% along the scale will not be an exact middle gray, its more likely to be nearer white/black.

 

i hope this makes sense, maybe researching linear graph's / scales and exponential graph's / scales will help explain what i'm trying to say, equally maybe someone else can put it a cross in a more understandable manner!

 

James

[Hallock]

i would have thought the glass is darker simply because you are now using an exponential curve for your exposure control against the previous linear control. This will make the same light levels appear different.

 

Unfortunately its not the easiest thing to explain, but in a linear fashion, if you have white at the bottom level and black at the top level 50% along the linear line will be an exact middle gray, hence it being linear.

 

on the other hand when the same scale is turned to exponential the graph line now curves so 50% along the scale will not be an exact middle gray, its more likely to be nearer white/black.

 

i hope this makes sense, maybe researching linear graph's / scales and exponential graph's / scales will help explain what i'm trying to say, equally maybe someone else can put it a cross in a more understandable manner!

 

James

 

I understand the concept, and that's why I use exponential, but in previous versions of V-Ray I'd used exponential and not had this problem with glass. I'd turn it on exponential and it would be clear, regardless of color. I guess because the exponential setting may not have previously affected reflections and refractions?

 

The settings are 100% default, to minimalize error in weird settings. The material has a refract of 255, 255, 255, everything is default. All else I've done under the renderer is simply change it to exponential color mapping.

[Hallock]

Can you post your material and lighting settings?

 

The settings are 100% default, to minimalize error in weird settings. The material has a refract of 255, 255, 255, everything is default. All else I've done under the renderer is simply change it to exponential color mapping.

[ramy]

I'm actually having the same problem. My background is a light blue, but through the glass when rendering exponentially, the light blue turns to the dingy dark blue that is found when you have "Affect background" selected. However I have affect background unselected and it's still affecting my background only through the glass....I'll keep playing with this.

[ramy]

Here is a simple example of the vray glass problem:

This image has a linear exposure and the background color is fine through the glass.

This image is the same image but with an exponetial exposure. The background through the glass becomes very dark even though my refraction is absolutely white. Does anyone have a solution to keep the background color?

[ramy]

ok, it didn't take long after my last post to figure it out:

Check the Override MAX under reflections/refrations in the Environments.

 

 

 

 

This takes care of the glass transparency color when rendering with exponential exposure.

[MAGANGLO]

Thanks, I've been having that same problem for ages - changing to vray overide for reflection/refraction and upping the multiplier sorted it