VrayMat as glass question - request

[j.galang]

Through a recent project I have noticed that using Vray Mat as a glass material is way faster than using a standard material with a Vray Map is the reflection slot. What I do is usually make the refract value of the Vray Mtl totally white and make the max depth at around 20 (this does not slow the rendering down I think). You can also give the refraction a tiny bit of color if you want to simulate real architectural glass (which has a a very small hint of green). Using this technique you can get fantastic looking glass edges also (that look like real glass edges) which are generally a dark grenish color. Coupled with a small refelction value this I think is the best way to simulate glass for houses and buildings and the speed is way faster than using a standard material.

Now. My only question is why is it always when you increase the reflection value, everything behind the glass looks darker? If refelction is 0, the glass is completely clear (with pure white in the refraction color). The thing is that all the glass I use have to have some sort of reflection. The higher the reflection, the darker the image behind the glass. I know that this might be the correct physical behavior of glass but it would be REALLY NICE if we can control the amount of light filtered by the glass. With the standard material and Vray Map in the reflection slot option, it is very easy to control this. Just play around with the filter colors of both the Vray map and the standard mat. The downside of this is that you get not so nice glass edges and more importantly VERY SLOW rendertimes compared to using a Vray Mtl.

If teh Vray team is reading this post, this option of being able to control how dark/light things appear behind a transparaent Vray Mtl. would be very helpful (even though it may by physically incorrect). By the way I have also played with the exit colors to no avail. If anyone has any insights to this matter please post your reply.

Thanks.


JG

[DanielBrew]

Now. My only question is why is it always when you increase the reflection value, everything behind the glass looks darker?

When you look at a object light bounces off that object and into your eye. If you look at an object through a piece of glass some of the light bouncing off the object is reflected back off the surface of the glass. This reduces the amount of light entering your eye.

This is why sunglasses are often have a mirror like surface, as well as looking cool it reflects some of the light away from your eye.

[DP]

yes, we too have found this and for even quite low reflection values there is a significant darkening of the glass (even with cast shadows turned off), which is a shame because it seems to produce a nicer result than the other method described here, but the darkening makes effect of the vraymat makes it often unusable especially for internal glass.

What we have found for the vraymap method is to turn off generate and recieve GI for that material, which does speed things up by a noticable amount, as does not having force 2 sided on for the material as well.