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lowkey
10-30-2005, 07:49 PM
Hi there,

I'm currently trying to figure out everything about ambient occlusion and I wonder if there is a good mentalRay (3.4) shader available for this kind of rendering. I found info about some thing called 'Dirtmap', which seems to be a shader pack or something. Can anybody point me in the right direction please? Does mentalRay support AO at all? :shrug:

Thanks a lot!

kapollo
10-30-2005, 11:16 PM
Well, there are two shaders for mr included with maya 7 and one included with maya 6.5
and as an addon to maya 6 but you've mentioned mr 3.4 so you don't need download anything. I haven't been using dirtmap, but from what I know it does similiar thing to mib_ambient_occlusion (that or similiar name sorry don't have maya with me atm ;] )
it's in mr tab in hypershade. To use it simply plug it into ambient color channel and tune it's settings et voila.

cheers
kapollo

lowkey
10-31-2005, 06:59 AM
Thanks a lot, I found it under mrNodes - Textures - mib_amb_occlusion. I wonder why a search in the Shader Reference and Manual didn't produce any results. mentalRay's docs should definitely be improved! :eek:

Mqdice
11-13-2005, 03:52 PM
hey, can you also render ambient occlusion with just software render?

PixelMachine
11-13-2005, 04:17 PM
You could do that if you had an ambient occlusion shader for Maya Software renderer. I never heard about something like that, so the best solution is to use Mental Ray instead, a fast raytracer with a very poor manual. :)

Mqdice
11-13-2005, 04:48 PM
oh ok... I tried my own shader for software render but I dont know if its right.I found this Utility in the hypershade, the lighting info utility, and tried to play with it together with the condition utility. I tried to make the shader, anything that the lights in the scene hits, it will make it color white and if it it doesn't, it will make it black. I dunno if its the same in mental ray.

By the way does ambient oclusion use the lighting setup of the scene or you usually make new lights for just the Ambient oclusion pass?

Pixero
11-13-2005, 04:49 PM
There is one occlusion shader for Maya software that I know of. (And one of the first I think)
Its called RayDiffuse and you can find it here: http://www.lightengine3d.com/index2.html

For Maya software version use the "Download v2.1" link.

jeremybirn
11-13-2005, 05:51 PM
By the way does ambient oclusion use the lighting setup of the scene or you usually make new lights for just the Ambient oclusion pass?

I think most people render an AO pass without any lights. The AO in MR is implemented as a texture. For a separate AO pass, you can map it to the color of a Surface Shader, or the Incandescence of other common maya shaders.

-jeremy

NitroLiq
11-15-2005, 05:14 PM
I was playing with AO last night with a simple dinosaur model on a plane and was wondering how raytracing and final gather affect the render. For example, with AO plugged into the ambientcolor of a lambert, all lights off. It renders fine in MR. If I have raytracing/FG on, the model seems to render fine but I get some splotchy artifacts on the plane, and this at production quality. I tried upping the rays from 500 to 1000 and still the same effect. Are AO passes usually done without these on?

lowkey
11-15-2005, 05:38 PM
As far as I understand the whole fuzz about AO, it's originally thought to be a quicker substitute for GI/FG, isn't it? I mean IMO it's just a different calculation method for ambient lighting, which sends out rays from the shaded geometry only, instead of spilling photons across the whole scene like GI and then sending out secondary rays from there like FG.

So, I guess it wouldn't make sense to use all of these methods in conjunction. Or did I get something wrong with the whole concept? :shrug:

anthonymcgrath
11-15-2005, 06:11 PM
i use the dirtmap shader - fast, easily controllable and tweakable for each shot. when its comped over my render its so subtle any flickereing or noise simply doesn't show up but when the dirtmap aint there it dont look right. I've applied it to the floor on my render and it enhances the shadows quite a bit more and the nice thing is you can set negative numbers so you can 'boost the darks' hehe!

current wip below showing the dirtmap - I'm rendering off sep ao passes using dirtmap but I think I'll get my copy of maya7 on my system and get into the rendering overrides as its something I adored about xsi but maya has never had till now...

dirtmap pass
http://img.photobucket.com/albums/v90/anthonymcgrath/frm260_dirtmap.jpg

beauty
http://img.photobucket.com/albums/v90/anthonymcgrath/frm260_colour.jpg

spray n mist renders (I know they're not ao-related but just including em)
http://img.photobucket.com/albums/v90/anthonymcgrath/frm260_water.jpg

http://img.photobucket.com/albums/v90/anthonymcgrath/frm260_spray.jpg

and finally the composite
http://img.photobucket.com/albums/v90/anthonymcgrath/frm260_composite.jpg

azshall
11-15-2005, 07:28 PM
You could do that if you had an ambient occlusion shader for Maya Software renderer. I never heard about something like that, so the best solution is to use Mental Ray instead, a fast raytracer with a very poor manual. :)

RayDiffuse by mark davies.

http://www.lightengine3d.com .. been around for since at least 2000 or 2001? .. Pretty nice actually, and has a MR version.


--
argh, you beat me to it Pixero.

azshall
11-15-2005, 07:29 PM
I've foudn the Dirtmap shader to be very nice and reliable. Quick too. I've had troubles getting the mib_amb_occlusion shader to even work. I can't get it to give me ANY occlusion no matter what I plug it into.

az

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