Problems with Yafray and glass

I’m farly new to Blender and just trying out a few things. At the moment I’m stuck using fluids and glass. When I use Blender internal render engine I get strange vertical artefacts in the fluid (no, it’s not because the fluid penetrates the glass, since I moved the glass away and still got the same artefacts.)

Trying to solve this problem I tried using Yafray instead of the internal render engine. After having had a rendered image that was almost completely black I found out, that I have to increase the energy of the area lamps I used.
The table the glass stands on is perfectly lit, but the glass itself and the fluid is way to dark. Does anyone have a clue whats going wrong?

Using internal render engine:
http://blendpolis.serverpool.org/a/glass_fluid2_788.jpg

Using internal render engine with rayshadow (without fluid this time):
http://blendpolis.serverpool.org/a/glass_rayshadow.jpg

Using Yafray:
http://blendpolis.serverpool.org/a/glass_yafray2.jpg[/img]

I’ve encountered the same problem with the internal render engine. For YafRay, you have to make sure that your Raydepth value is high enough. In the YafRay properties tab you can increase the Raydepth value.

What is high enough in this case? I used 5…

I’ve seen the same issue with the glass/splash/liquid tutorial (black liquid and artifacts). In another thread it’s suggested (though more in response to fluid going through the obstacle) that it might be related to the fluid simulation resolution and the size of the fluid domain.

I’ve also had some glass rendered darkly because translucency was turned on…

I used raydepth of 11 now. The render definitely has got more reflections but the glass and the fluid still are very dark…

Translucency was turned off for both the fluid and the glass, the whole time, so the error has to be somewhere else. However, the artefact seem not to occur from what I can see, though the affected area is still quite dark.

Yafray with raydepth 11:
http://blendpolis.serverpool.org/a/glass_yafray3.jpg

Raydepth
http://www.yafray.org/forum/viewtopic.php?t=97

You have just a glass on a plane in the
whole scene correct?

No. As you can see in the render, there is also some fluid in the glass. Which greatly increases the needed raydepth, I think.

EDIT:
However, I just renderet the scene with 3 spotlights instead of arealights. It does light brighter, wihtout the shadows of course. The fluid, that is visible through the glass is still quite dark, though. So it’s the material settings?? Has anyone got good settings for glass and water? I used the clear glass preset…

Yafray with spots:
http://blendpolis.serverpool.org/a/glass_yafray5_spots.jpg