I was fooling with trying to get an 8x10 photo from Vue and did some renders at 3,000 x  2,400 pixels at 300dpi and turned off anti aliasing, now at the screen resolution I use 1200 x 800 the picture is grainy and larger than the screem, but if i reduce the image size it smooths out the image nicely while retaining detail, in my opinion a better result that  if I had rendereded it at 1200 x 800 with anti aliasing.  What are the downsides of doing this? and if I got an 8 x 10 print at say Walgreens would it look like a photo, especially grainwise,  taken at that resolution from my camera which takes about the same size image?

Rendering at higher resolution without AA, and caling the image down in Photoshop using "bilear" sampling does indeed the antialiasing for you. This trick is used by major studios to cut down their rendr times. Takes less time to render bigger without AA, but somtimes it is not satisfying. But works most of the time.

This has been my experience with most 3D apps I've used...they all seem to render so slowly at fine AA settings. This method was actually suggested by the makers of my first 3D program as they themselves were unhappy with render times and it didn't[IMHO]seem to impact on quality for some of the I had printed after doing the render large and as bruno suggested, running it through PS to get the correct print size.. ...

Rendering at twice the desired size with no AA and then resizing usually works for me.  It saves untold hours.  I often render at Preview and it works fine.  

Well, preview is certainly not good enough for all other parameters: transparency,reflections, atmospheres, indirect lighting and shadows, to name a few...

Quote - Rendering at higher resolution without AA, and caling the image down in Photoshop using "bilear" sampling does indeed the antialiasing for you. This trick is used by major studios to cut down their rendr times. Takes less time to render bigger without AA, but somtimes it is not satisfying. But works most of the time.

Bruno could you please explain how to do this for me. I have used PS for 12 years but I don't know this trick. What settings do I need and in Photoshop what do I use "bilinear" or something? Thanks

Ok, my photoshop is in french, so maybe I won't use the right words for the commands, but you can downsize your image by using the resize command from the image menu, just as you would resize any image. There you have different resizing options when ticking the "resample" box . Bicubic is on by default, but from the drop down list you can change this method to bilinear. Bicubic sharpens the image while resizing, and bilinear smoothes out the image which is what you are looking for if your render isn't anti aliased. In CS2, you also have "smooth bicubic" I haven't tried it, maybe it is as good as bilinear.
Again, the translation may not be accurate.

Along a similar line - I have been using Genuine Fractals Print Pro for years. I usually print on 13 x 19" paper. There are times my images have been as small as 2200 x 1600 pixels from Vue. You can work with downsizing your image and then making it larger if necessary. In GFPP you can work with a sharpness slider also. I have mine turned off. I am very picky about details and colors. I reviewed it when this version came out.
http://www.perpetualvisions.com/renderosity/review-gf5printpro/review-gf5.html

This program has been wonderful for me, and I've mentioned it before in this forum.

Indeed I meant to bring up the PS plugins...at work we had another one as well that was as good tho I don't off hand remember the name but I think Paula mentioned it in her review. I thought it worked better but the AD decided to go with GFPP.. ...