Frosted glass oddity

[thomthom]

I did a quick test render and noticed something unexpected with some frosted glass I had in the scene. As you see in the attached image, the frosting clips where there's a regular window infront of it. Any clue to why this happens?

The frosted and clear window materials are based on the sample materials that came with V-Ray. The rest is just plain SU materials.

[dalomar_cg]

Re: Frosted glass oddity

To be honest, I'm not sure which part you're talking about. So if you could point that out a little clearer that would be helpful.

Off of the top of my head I think it might be 1 of 2 things. First is that the glass isn't modeled as a solid, but is just a simple plane. Its really important for refraction to have an entrance and exit surface, so without that some interesting things can happen. Second thing is that you may need to increase your Max Depth as that might be cutting out refractions too early.

[thomthom]

Re: Frosted glass oddity

The problem is the frosted glass seen in the image, a little to the left. In the model it extends down to the flooring. All the glass objects are closed square boxes.

When you say Max Depth, what are you refering to then?

[dalomar_cg]

Re: Frosted glass oddity

Okay thats what I thought it was, but it kinda looked like it was randomly placed, so I didn't know what it was supposed to be doing.

Max Depth (its in Global Switches) is a setting that will tell V-Ray how many reflection/refraction bounces to calculate before it cuts off the calculation. By default its set at 2 for speed, but once you start getting refractions through refractions and things, then you hit that ceiling pretty quick. A good all-purpose quality setting is to have it between 6-8 and if you come to a situation that needs more, then increase it (usually only for jewelry stuff though...not really archviz). If its still at 2, then I'd say thats the culprit, but if it isn't then post back.

[thomthom]

Re: Frosted glass oddity

Upping it to 4 worked!

So, if I want to render an image where I look down a row of these, the Max Depth needs to be at least the number of faces overlapping each other? The image is showing one module of the house which is repeated about 5-6 times.

Also, when I make my windows I make a window frame and then I insert a solid box acting as glass. But since the edges of the glass is coplanar with the inside of the window frame, can I then delete these edges? Would it be enough with just two faces opposite each other?

[dalomar_cg]

Re: Frosted glass oddity

No you can't delete the edges. V-ray needs a way to know that the entrance and exit surface are connected. The only way to do that in SU is to have them as a joined solid...Give me a few min and I'll track down an example from the beginning of the summer.

[dalomar_cg]

Re: Frosted glass oddity

Here's a post by Micha where he was asking the same thing essentially (separate surfaces not max depth). We went back and forth for a few posts, and in the process the entrance exit thing gets explained a little more fully and in a practical example. Its Rhino specific in some parts, so I'm not sure how everything would get translated to SU, but its a good reference I think

http://asgvis.com/index.php?option=c...11201#msg11201

[thomthom]

Re: Frosted glass oddity

I see. That's what I was suspected.

However, would it be enough to have lines connecting them, and remove only the edge faces? If it's solely to make V-Ray work out what's connected...?

The reason I ask is that my glass component is repeated hundreds of times around the building. I figured I might be able to save some polygons if I could remove the edges.

[dalomar_cg]

Re: Frosted glass oddity

I don't think that having lines connecting them would work since we don't actually read those when we export the geometry.

I see your point with the extra polys, but realistically you're only looking at 8 "useless" polys per window. So you'd have to have several thousand windows in order for that to have a truly adverse affect on the poly count. Chances are there are better places to save some faces.

[thomthom]

Re: Frosted glass oddity

Understood! Thanks for shedding some light on this.

One last thing. From what I gather from the manual, glass material should be 2-sided? Or will that cause extra refractions? Or is it required in order to make the exit refraction work?