Glass, very long render times. What's your settings?

[danieljhatton]

When I render this scene with my 5mm box for glass I get extremely long render times, even to the point of infinity if I mimic double glazing. When I hide the glass altogether I get very fast render times. The area that is effected is where the sunlight hits the floor, any other in-direct areas are fine.

Rendering wise I am using BF+LC, 0.01. LC for glossy's 2500 subdivs @ 2500px. Everything else in vray is pretty much default, nothing wacky going on. Usual EXR Vray Dome Lighting, Physical Cam, No other lighting. Below are the settings I am using for the glass object and material. Where am I going wrong? Is using a box for glass wrong? Do I need to be using a simple plane? Is my set up for Vray Object properties wrong?

With Glass. Just gets stuck on light, takes forever.



Without Glass. Render V Quickly.



Vray Object Properties



Material



Simple Extruded Rectangles, 5mm

[danieljhatton]

Scene render.

[simmsimaging]

You should try setting the diffuse to pure black (0.0.0) and if it's real glass I think you might want to turn on fresnel reflections (and unlink it from the refract IOR because you have that very low).

b

[danieljhatton]

Brett. Thanks a mill. I will give that a try.

[vlado]

You can also try giving the material some glossiness (very slight, like 0.99) for reflections and refractions, with low subdivs (something like 2 or 3).

Best regards,
Vlado

[rikou]

You can also try giving the material some glossiness (very slight, like 0.99) for reflections and refractions, with low subdivs (something like 2 or 3).

Best regards,
Vlado

Just for good understanding, how can that help ? I mean put glossiness to 0,99 with low subdivs ?

[Donald2B]

You may also want to turn on affect shadows under the refraction area.

[simmsimaging]

You may also want to turn on affect shadows under the refraction area.

turning this on affects caustics somehow though doesn't it? I recall there being something with using that option and caustics conflicting. Is that correct? IF so does it apply to photon mapped as well as GI caustics?

[Donald2B]

Ugh...I don't know....I rarely use caustics. I will have to look into it more. Almost all of my glass is setup similar to yours with the black diffuse, etc...

[simmsimaging]

Yeah - it does affect it. Here is a snip from the link below (good tutorial overall btw)
http://www.aversis.be/tutorials/vray...ettings_02.htm

"Turn affect shadows OFF and render again. Notice the shadows are different now. This is because the GI caustics come back into play. This image is the physically correct one! When you have the affect shadow option turned ON, no refractive GI caustics are computed for that material, they are automatically turned off by Vray. The affect shadow option is nothing more than a 'fake caustics' option. So imagine that when using the affect shadow option, refractive caustics would not be turned off automatically, you would get a fake caustic effect AND a real GI caustic effect on top of each other! That's why Vray automatically turns off GI caustics for materials that have the affect shadow option turned on. THIS IS VERY IMPORTANT TO UNDERSTAND!

Use the affect shadows option when you want light to pass trough refractive objects, and you don't want to enable refractive GI caustics, or when you don't use GI at all, or when you're using Max lights. Max lights will never produce refractive GI caustics! So if you want the light of max lights to pass trough refractive objects, you MUST use the affect shadow option."

/b

[Donald2B]

Yeah, that is a great site! This is usually why I turn it off then, because we rarely use caustics due to time constraints.

[nils_p]

It seems you have a gradient ramp in the bump slot. I've had some trouble with gradient ramps in the the past.
You could try using a bitmap for that. See if that helps