Problem with transparent material

[SCR73]

I am a beginner user of the "realistic" visual style and I'm having some problems with transparent materials which appear kind of checkered or stripy. I've tried changing a bunch of different things fairly randomly but nothing seems to make much difference. My soild materials look okay.
Any sugestions?

[jaberwok]

Make sure you do not have two objects occupying the same volume of space.

[SCR73]

Thanks for the suggestion Jaberwok but that's not it. This is the third project that I've done with a transparent material and the same thing always happens. I thought it might be our new printer (which I have never liked as much as the old one) but I tried a printer on the other side of the building and it was no better.
I also tried plotting to a PDF (I was planning to post it here so that you could see what I meant!) and it looked even worse than the printed one. The material was mostly solid with just a few patches of transparency where there is another object behind it...very bizarre.

[jaberwok]

Does the material contain any maps? Is it any better when rendered?

[SCR73]

No maps. I actually thought of that one myself :) . It did have a diffuse map but I removed it and it didn't make any difference.
I thought maybe it had something to do with my "glass" being about 250mm thick so I turned it all into regions instead of one solid and then erased all the back faces. That didn't make any difference either!

I've never tried rendering. I'm not actually sure how!:Oops:

Oh well, the stripes didn't bother my boss as much as they bothered me so we've issued the drawing anyway. I would still like to figure it out for next time though! Maybe I'll try to work out how to do rendering when I next have some free time and see if that comes out better. Thanks for the suggestion.