View Full Version : mental ray / xsi for still imagery?

kidult one
09 September 2006, 09:54 PM
Is mental ray a purely a animation renderer or is it just xsi that does not cater for the print market? I cant seem to change the resolution of my image from 72dpi - this is to low a resolution for printwork so now at the moment I have to render out massive images and scale them down. Are there any people out there using xsi for printwork and if so could U share some insight?

09 September 2006, 09:59 PM
Mental Ray is a robust renderer that is suitable to print work, but is focussed on animation work.

The dpi setting is really a pointless setting until the image goes to print, and you can simply and quickly change the dpi setting in Photoshop (where you will likely convert the image to CMYK anyway). There is a whole conversation on it in the Beginners Sticky at the top of the XSI forum.

09 September 2006, 10:18 PM
BTW: That discussion starts at post 372 and goes on for a bit.

09 September 2006, 11:49 PM
What kind of print work are you doing? We should have asked that first!

Well it was very small print work, but I just did a CD cover using XSI (300dpi 2.8Ghz dual core dell junk machine). Used some BHairy in it as well. Often in print it's easier to do passes etc. and combine it all in PS, even if it's just bootimouse passes than an animation.

I'd say that XSI is great for print work- just make sure to do you homework on using MR "correctly". More RAM is always better- but I find that XSI will render out stuff even if I don't have "enough RAM".

We'll see though- the people I did the CD cover for want tabloid size posters for kiosks now! I used Final Gathering for their CD cover (not really needed though) but after reading a few threads here, and getting the TS and plugins I think I'll be able to do that as well.

The great thing about using FG for print work is you don't have to worry about flicker, and can clear things up in PS if need be while getting away with some quick and dirty FG settings.

You might want to look into one of those fractal enlargment plugins for PS as well. Many people render out at say 80% of their final work, and then go up to %100 with the resizing software. Saves time and money. Toss in some noise (if needed) and print.

Also- think outside the Adobe Suite box on this a little. In PS, make an image that is the final size of print job (if your 3D elements are edge to edge). Make it 300dpi (if that is what you are going out to) and then look at the image size- how many pixels is it? Now in XSI all you need to do is a custom cam, and make sure the aspect ratio is 1 to 1 (square pixels). That is all you need to really do in the end.

So in other words if I have a 3D element for the final print comp, that is 4" by 3" at 300dpi the render for that element needs to be 1200 X 900. Again, unless your 3D elements go edge to edge I suggest you break it down into parts if you can and work with it that way. I find it much more flexable than rendering out each element at the whole documents DPI- and your machine with thank you with faster times and less ram needed IMHO.

kidult one
09 September 2006, 08:01 AM
JDex -thanks having a read-thru

Mocaw - Thanx for all the info - glad to see I was on the right track as I have been doing the rescaling thing - didnt think of the 1 to 1 camera aspect

My only problem with this is the rescaling issue as it is never 100% (bit of a perfectionist on these things) could u name some of the fractal enlargement plugs or where i could look?

Then hate to do the software compare thing and wil spare names but in my previous app changing the dpi had little or no-effect on rendertime so it cant be a major thing to adjust on an image during render?

09 September 2006, 06:36 PM
Someone should do a wiki entry on DPI cause its so often misunderstood.

DPI (dots per inch) is completely relative. Meaning you can change this number without actually changing the size of the image. It is meaningless in 3D rendering and applies to print as a pixel ratio vs real world measurements. You do not rescale (enlarge or reduce) an image to modify its DPI. If you must, it is always better to scale down than to enlarge.

-You probably already know your output (print) size. Lets say its 4h x 6w inches.
-You know you want to print at 300 DPI.
Your render output should be at least (4 inches * 300 pixels)=1200px high by (6*300)=1800pix wide.

So, that being said, No matter what software is used, no matter wether the render settings are in pixels or inches and DPI, Whatever the platform, the renderer will output 1200*1800, because thats the amount of pixels you need to print a 4x6 in 300dpi.

print length in inches * desired output in dots per inch = needed pixel resolution.

09 September 2006, 08:17 PM
You do not rescale (enlarge or reduce) an image to modify its DPI. If you must, it is always better to scale down than to enlarge.

Very true, but depending on the deadline, the client, and the image, sometimes you have too/can enlarge slightly with the correct software. As always though you'll need to see how it looks in print before saying it "worked". I know this is far from ideal though and agree that there is almost never an issue with downsizing.

09 September 2006, 09:33 PM
We used Genuine Fractals Print Pro for upres-ing our Jimmy Neutron banners.

And for my $.02 on DPI, the only time I found it to be a factor (needed to be 72dpi) in After Effects is when copying/pasting paths from PS->AE. If the PS document was anything other than 72dpi, the path/mask would be scaled..

09 September 2006, 12:59 AM
There are also blow up

and enlarger pro (cheap but works, yet not as flexable).

09 September 2006, 02:25 PM
From my experiences, a good rule of thumb would be to render larger than the final output needs to be.

For example, I have to submit stills that are 8 1/2" X 11" for print @ 300 dpi. Following the calculations mentioned in the posts above, that would create renders 2550px X 3300px.

Take that into PS, and you'll get usually a file that's about 30-35mb. Unfortunately, a lot of agencies ask for a minimum of 40mb (or more).

What I usually do is render the images to a 15" X 12.5" (or thereabouts) size, which gives me roughly a 50mb file. That pretty much answers all of the requirements of the agencies, and that way they have enough data to scale up the images if needed.

In PS, create an image with the proper pixel dimensions, then go to Image>Image Size... and uncheck Resample Image. Then, you can specifiy the proper dpi and size in inches (not that we need it, but again, some of the agencies require it).

And when scaling down in PS, you don't lose any information, so that always works.

My 2 shekels...

p.s. RAM is always good :-)
p.p.s. what are the plugs mentioned that you would use for this kind of work? I'm relatively new to XSI, and I'm still a wee bit lost in the addon's world...

09 September 2006, 02:52 PM
Speaking of must have addons for print... Helge recently released an output shader called output_savefile which you can use to force Mental Ray to save the render as a targa on very large renders, before the renderer does the final rendered file save... this is awesome because of MR's tendancy to crash due to lack of memory during that final step.

This is a shader which saves the rendered image as a TGA file (raw / uncompressed). The shader has been implemented because sometimes mental ray crashes when rendering very big images (8k x 8k for example). In most cases the output shader is still called, that's why I implemented the TGA saver as an output shader.

Check it out at

09 September 2006, 02:57 PM
Thanks for the head's-up. I'll definitely give that addon a spin.

09 September 2006, 12:06 AM
I'm a bit confused on how to install the ouput_saveFile addon...
Is my User folder supposed to only have directories with nothing in them?

Any suggestions?


kidult one
09 September 2006, 06:46 AM
any way to get a preview window when doing these large files?

and anyone know good inch to centimeters conversion tables? (inches suck - metric rules)
everything on this side is in centimeters - this damn coverting to inches and then figuring out my image size sucks.

09 September 2006, 01:07 PM
If you want to get 50 mb files, following the calculations mentioned above, you can use a size of 4790px X 3700px.

That should give you 40.56cm X 31.34cm @ 300dpi.

A standard 8.5" X 11" sheet in here in North America would translate to 21.59cm X 27.94cm.

I'm not familiar with the standard sizes you use on your side of the pond, but Photoshop will allow you to do some quick calculations in the image>image size...

Hope this helps.

09 September 2006, 04:22 PM
p.s. RAM is always good :-)
p.p.s. what are the plugs mentioned that you would use for this kind of work? I'm relatively new to XSI, and I'm still a wee bit lost in the addon's world...

There are some good shaders here that can speed things up (like blured reflections):

and the shaders you'll have to do a search for. But ctrl.buffers, ctrl.rays, and ctrl.irradience are some of my top picks- but there are many more!

09 September 2006, 11:44 PM
I've been looking for some of shaders, but can't seem to find any working links (looking for ctrl.rays and some of the others mentioned in this post).
Did find some for Maya though...but this doesn't help really.

Any suggestions, or better yet, a site that might have them?

And if mrs. is(are) reading you guys have a website documenting your work? From what I've read, you seem to be the forefront of MR development. Keep up the excellent job.


09 September 2006, 01:20 AM
Well my spelling doesn't help! Here is what I could dig up-

Post #49

Don't know if this is the newest version...

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