From: wave@waits.media.mit.edu (Michael B. Johnson)
Newsgroups: comp.sys.next.misc
Subject: Re: RenderMan-High resolution rendering?
Date: 12 Nov 92 05:06:29 GMT
Article-I.D.: news.1992Nov12.050629.26616
Organization: MIT Media Laboratory

Charles Fletcher writes
> 
> I have a question about RenderMan (specifically prman, which I would guess
> will be answered by MJ-hi Michael-but I'm  posting it since I thought there
> might be general interest.)

Hi Charles.

> 
> 	How can you get high resolution images out of the NeXT?Well, first I'll  
assume you're either 3D competent (i.e. you understand the 3DKit and can list 3  
reasons why what Dave Springer did is hard) or you're using one of the 3D apps  
that are beginning to appear.  My personal favorite so far is 3D Reality  
(blatant plug) from Stone Design.  Either way, let's say you've modeled  
something, have applied a shader, and have now saved it out to a RIB file.  A  
RIB file is the RenderMan equivalent of a PS file in PostScript - it's an ASCII  
file you hand to RenderMan (the same way you have an ASCII file which you send  
to a PostScript interpreter) and ask it to give you back bits.  

OK, so now you have a rib file, let's say foo.rib.  Since it's just an ASCII  
file, you can edit it with your favorite text editor.  Open it up.  The first  
line you'll probably see will be something like:

Display "/u/wave/tmp/foo.tiff" "file" "rgba"

Where foo.tiff will be the name of the file that will be written out.  A few  
lines later you'll see a line like:

Format 256 128 1.000000

Here's where you could change the resolution of your image from, say, 256x128  
to whatever you'd like (2048x2048?).  

A little bit later, you'll see a line like:

ShadingRate 10

This is the number which (basically) tells prman how many times to call your  
shader in its shading loop.  The smaller the number, the higher quality the  
image.  The lowest number you should ever use is 0.25.  My understanding of  
this number says that 4 samples per pixel will be taken (i.e. 1/4 == 0.25),  
given a wicked sweet anti-aliased image.  Unless you have very high frequency  
shaders and/or you need really clean output, use a higher number (like 10 or  
so) to get a feel for your image before the final rendering.

>	 That is,
> 	images that are photo quality (and saved on slides or film, or
> 	Kodak Photo CD to touch on another thread.) Are there bureaus that
> 	do this as a service? 

Photo Quality is a slippery term.  That really depends on your output device,  
which really depends on your equipment (or service bureau).  Some take 8Kx8K,  
some take 2Kx2K (and make it look like 8Kx8K...), or whatever.  Still images  
always want higher resolution than moving imagery, so that matters too.  

In other words, it depends...

Also realize that PhotoCD is takes an analog image (film) and puts it in a  
digital form (5 varying resolution images on a CD-ROM).  This is the opposite  
of what you're talking about doing, which is taking digital imagery and putting  
it to an analog form.  Kodak has yet to address this with PhotoCD (other than  
to say you could go to a photofinishing store and specify your reprints there).


> Should the image be converted to PS first?

Check with the service bureau, but off the top of my head, I'd say No.  If  
you're going to a service bureau, TIFF will probably be as acceptable (or more  
so since it can be compressed, which makes it easier for you to transport it  
there in the first place).


> 
> 	This may actually be a moot point: My second question--How much
> 	(disk) space is required to do a high resolution image (say, 
> 	1000 to 2000 dpi range)? (BTW-what is the resolution of the images
> 	in the RenderMan Companion?) I have yet to render even a simple
> 	scene at 400 dpi without running out of swap space (I have a single
> 	330M disk with about 50M free for swapping). Any tricks (like tiling)
> 	to help do this? Maybe I should run off my OD and simply use the
> 	HD for swapping!-)

Charlie - supress the urge to do things at 400dpi, unless you are doing things  
that are only an inch or two wide.  For rendering, think in pixels, not dpi.   
You screen is probably (at most) something like 1200 x 900.  RenderMan is  
piggish, but remember that Tin-Toy was done on 8 meg to 32 meg machines.  There  
are some "tiling" commands in RenderMan, but off the top of my head, I don't  
remember them (all my RMan doc is at home).  I'll try to remember to post them.  

Hope this helps.  


--

-->  Michael B. Johnson
-->  MIT Media Lab      --  Computer Graphics & Animation Group
-->  (617) 253-0663     --  wave@media-lab.media.mit.edu
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