This is a fragment of a picture I was going to put in the Challenge Gallery for the current months challenge.

I have attempted a glass of gingerale on a rough surfaced glass table. You can see the rough table reflecting the blue of the sky. Notice though that looking through the gingerale glass the reflections of the sky on the table are not visible! Instead we can easily see through the table to the bricks underneath.

Am I the lucky winner in the new bugs catagory or is this a known problem. Anyone have a solution?

Thanks
Ed

The angle of inflection is downward from what I can see. So you should see something that was lower than the level of the gingerale through the gingerale(via refraction). I can't really make sense of it as I only see the top third of the glass (tumbler).

Ok the pict cane through but I still don't see the table.

Here is the full image so you can better see what is going on. I think the problem will be obvious.

Oh yeah now I see what you're talking about. You can see the rim of the table in the tumbler so its just not picking up the texture of the table in the tumbler. can you up the refraction of the table or make it a little less transparent? Anyrate check the refraction values of the tumbler and the table, check all the tumbler and tables rendering preferences (C2 manual p 531 - 4 and 5 under setting an objects rendering prefs.) It looks to me as though the problem is with the table but I'm not certain. Sorry not to be of more help, - TJ

Ed,

It definitely a bug. I was able to recreate it with a very simple scene.

Best regards,
Eric Winemiller
Digital Carvers Guild
3D extensions for Carrara
http://digitalcarversguild.com

Does it only happen at certain angles?

Thanks all for the help. Maybe I can come up with a workaround. The amazing thing is that I probably rendered this 20 times without noticing the problem! DOH!! Thanks again, ED

ED, I was curious about it. set refraction in the shader to 1.33(not sure exactly how I got to the I.R. setting. I was just playing around - I'll have to do it again if you need to know) and it didn't duplicate the problem. is your glass about 1.6 and your water(ginger ale) about 1.3? looking in the ginger ale in your render the refaction appears to be ok so it might either be the tumbler's I.R. is off. As ewinemiller duplicated the bug this might not help but any time someone mentions refraction or spirals, I gotta fool around with it, anyway. - TJ

TJ I think you were right on with your first suggestion and after preliminary attempts it appears not to be a bug! I moved the attenuation and depth sliders for reflection and refraction to mid values. A "plop" render seems to indicate the problem is resolved but at GREAT expense in rendering time. (Expected) I probably should have mentioned that I am using the fresnel plugin from Lost Horizons for the tumbler and that does not seem to cause problems. I will mess with settings and see if I can pick up the rendering speed and report back if you wish. Thanks: again once again the forums experts come through! I was ready to ditch the project!

Ed Please let me know! after all I'm just learning all this stuff... come to think of it I moved the depth way up in my experiment too. Glad you got it solved - it looks like it's gonna be a great model and render! - TJ

I haven't come across this problem in Carrara, but haven't really done much with refraction. That said, in RayDream, if you had a refractive object in front of a refractive object, the foreground object's refraction would prevail, eliminating the refraction of the background object. This may be related to that effect. You might work around that by rendering scene without the glass in it, set that render as your backdrop, then render the glass with everything else invisible and with an alpha channel. Do a third render of the entire scene and composite all of them together and photoshop the hell out of it to get the reflections of the cherries and such all to work out. Not a pretty solution, but it would work. Hope that's helpful. It's an awesome model; the texture for the glass tabletop is awesome! - Dex

I'm still trying to refine the settings but the render times for small plop renders are running into the hours. I may be resorting to compositing yet. Thanks for the help.

Attached Link: http://www.renderosity.com/viewed.ez?galleryid=423129&Start=1&Artist=sailor%5Fed&ByArtist=Yes

Finally got it to render. The solution seemed to be increasing the "depth" on the tumbler and table reflection and refraction, but I was in a hurry to get this out so I didn't spend a lot of time refining the settings. Just went with what worked! There may still be a bit of wierdness but if so it's not too noticeable IMHO. Thanks again for the help. Happy Ed!