Re: How MR cooks together final image

[Tauno Ööbik <tauno(at)joonisfilm.ee>]

Thanks for the scheme, made the picture little bit more clear. Where does FG or ambient environment probe pass fit in here? My first thought says to use FG in diffuse lighting pass. But problem comes if there are many lights, how should FG and diffuse lighting be mixed together? Same question goes also to environment probe pass.

For diffuse lighting, what kind of shading makes sense to use there...just pure white shader of my own choice?

If using bump, this should be seen only to shadows, reflection and spec pass right as I see it?

Thanks,
-T


Andy Nicholas wrote:

Generally, most layers need to applied either in multiply or additive mode.
In Photoshop, watch out because Screen isn't additive, you actually want
Linear Dodge which is additive.

Off the top of my head, you can break layer order down like this (top to
bottom):


Reflections (Additive)

Loop for each light, and add the final result with the layers below
{
	Specular (Additive and masked by the light's shadow)
}

Loop for each light, and multiply the final result with the layers below
{
	Shadow (Alpha Composite)
}

Diffuse Lighting without shadows (Multiply)
Occlusion (Multiply)
Color


That's assuming that you want to break it down into that many layers. It's
probably overkill for most people.

Andy



 

-----Original Message-----
From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf Of
Tauno Ööbik
Sent: 28 March 2007 21:51
To: XSI(at)Softimage.COM
Subject: Re: How MR cooks together final image

Ok, good to know. But the question still remains :/ Or I'll try to rephrase
my question. What should I investigate to get better understanding about the
requirements of compositing right layers in right order. Of course, before
comping right stuff needs to be output. Should I look to renderman world for
it. Is there more info available? Since everywhere in facilities guys are
comping together complex scenes. Where from do they gain that knowledge.
Only cause some guys in the " inner circle" know about it and are only
sharing it to other who also are in the "circle"?

-T


Andy Nicholas wrote:
  

Mental ray doesn't composite layers to produce the final image. Mental 
ray illumination shaders like Blinn only have one output (color), they 
don't channel the components out to separate channels to be composited
    

later.
  

Don't get confused by the user framebuffers. Shaders will write to 
them only when requested to. They don't form part of the rendering 
pipeline to produce the final image.

Andy


-----Original Message-----
From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On 
Behalf Of Tauno Ööbik
Sent: 28 March 2007 18:56
To: XSI(at)Softimage.COM
Subject: How MR cooks together final image

Where from can I learn more about the topic how MR internaly builds 
together final image. IE in what order does it calculate sub-passes, 
and in the end how does it put together all the layers together for 
final image. I am looking that info to get better understanding about 
the internals of MR and in the end to use that info to put together 
more efficient passes for compositing.

I already took a look to the well known book called "Rendering with 
Mental Ray" but unfortunately this topic is covered insufficiently 
there. Or I missed the right spot :)

Unfortunately, right now I learned more about that topic from here 
then from that book:
http://www.jupiter-jazz.com/wordpress/wp-content/data/tr4kv2/html/chap
ter3-S
OFTHARD.html

I just wanna shorten my work days which are growing way tooo long as 
the bar needs to be risen again and again constantly.


Thanks a bunch,
-T
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